Bibliothek

Notizen: The ligninolytic fungus Phlebia radiata growing in a low-nitrogen medium with wheat bran as the sole carbon source was induced by some lignin monomers, e.g. vanillic, veratric and ferulic acids. In the medium these substances showed a mainly stimulating influence on the hemicellulolytic enzymes activity except for arabinofuranosidase and ferulic acid esterase.

Notizen: This paper approaches the problem of oxygen mass transfer. This transfer is in antibiotic biosynthesis liquids produced by microorganisms belonging to the actinomycete and fungi classes, which exhibit a shear thinning non-Newtonian rheological behaviour.The volumetric oxygen mass transfer coefficients in these liquids (kL ab) change during biosynthesis processes. The change is mainly due to rheological parameter modifications, such as increasing the consistency index (K) and decreasing the flow behaviour index (n). The values of kL ab were 3.0-6.5 times lower than those recorded in water, and their decreasing depended on the kL a values obtained without biological liquid and on the nature of fermentation broths, as well.Starting from experimental data, two correlations were established between kL ab and P/V,υSG and P/V,υSG, N, respectively. These correlations contain a dimensionless factor (ηam/ηg)a6, which takes into account the rheological properties of the liquid phase and offers the possibility for a fast and sufficiently accurate estimation of kL ab. The empirical correlations developed in the paper correspond reasonably well with the relatively wide variety of experimental data, as in the model proposed by PEREZ and SANDALL, and allow for the comparison of the fermentation batches of the same or different microorganisms; also, they may be applied to the workings of design, scale-up, control and monitoring of bioreactors.

Notizen: A covalent binding to cellulose granules of two yeast strains Candida tropicalis and Trichosporon cutaneum was achieved. The maximum activity for destroying furfural by the immobilized cells was obtained when the procedure conditions were: reaction medium at pH 5.0, 20°C and cell suspension concentration of 80 mg/ml. The continuous furfural transformation was studied using a growth medium in a fermenter with immobilized Trichosporon cutaneum in which a 84% bioconversion was achieved. The reduced values of furfural remained constant even after 10-fold transformation.

Notizen: A thermophilic bacterial mixed culture was isolated from spent liquor of pulp mills, using a chemostat under aerobic conditions. It consists of two components belonging to genus Bacillus. The thermophilic Bacilli were cultivated aerobically and continuously at 67-70°C and pH 6.8-7, rising the percentage of spent liquor in stages. The dilution rate ranged from 0.2 to 0.33 h-1 during the experiments. The composition of the cell mass produced was analyzed.

Notizen: The growth of different strains of Pleurotus spp. on sugar cane agrowastes was evaluated. Three hybrid strains with good production outcomes and yields exceeding 17% were selected. Strain 184 (P. ostreatus x P. pulmonarius) showed the best results.Three spawn materials (wheat grain, millet grain and milled corn cob) at different spawning levels were tested and a significant influence was found. The obtained results were best explained in terms of total nitrogen content of the initial mixture (spawn + substrate), suggesting a probable nitrogen limited growth of the mushroom on sugar cane residues. A 10% millet grain spawn was found to be a reasonable compromise.Productive responses decreased with an increase in bag's capacity (8-10-12 kg), even though the same diameter was maintained in order to avoid pronounced temperature profiles. Smaller bag's capacities (8-10 kg) were recommended.It was also shown that the utilization of water hyacinth (Eichhornia crassipes) mixed 50/50 with sugar cane residues as substrate caused a twofold increase of crop responses, confirming the advantages of this substrate supplementation.The obtained results identified sugar cane agrowastes as a feasible substrate for Pleurotus spp. production with yields and biological efficiencies comparable and to some extent better than others reported with conventional lignocellulosic residues such as cereal straw.

Notizen: Optimization studies have been carried out for the production of L-lactic acid from the fermentation of beet molasses by Lactobacillus delbrueckii. A PLACKETT-BURMAN Design and a Central Composite Design have been used to determine the most suitable nutrient medium for obtaining a maximum cell concentration. A second-order polynomial empirical model relating both the cell and nutrient concentrations was formulated. The variables selected for the study were Yeast Extract, Peptone, Tween 80 (antifoam), MgSO4 · 7H2O, MnSO4·4H2O, FeSO4 · 7H2O and K2HPO4/KH2PO4. Among them, only Yeast Extract and Peptone were found to significantly affect the cell concentration. A maximum cell yield was found when the concentrations of Yeast Extract and Peptone were, respectively, 5.31 g/l and 5.08 g/l. All conclusions are restricted to the experimental range studied.

Notizen: The biodegradation of leguminous and non-leguminous organic materials by Pleurotus sajor-caju and P. ostreatus was studied. Comparisons were made between mushroom yield on both types of substrates. The conversion percentage from dry substrate to fresh mushroom (biological efficiency) was determined. Mushrooms were analyzed for their protein content, carbohydrates, percentages of ash, fat content and crude fibre. The energy value of fruit bodies was computed. The yield obtained from leguminous substrates was significantly high as compared to that yield which was obtained from non-leguminous substrates. The lowest yield of P. sajor caju (10 g ± 0.3 g) and P. ostreatus (6.5 g ± 1.2 g) was obtained using the Bougainuillea substrate and the highest one (519 g ± 16 g, P. sajor-caju and 488 g ± 18 g, P. ostreatus) using nitrogen-fixing leguminous Leucaena leucocepholea. The nitrogen content in fruit bodies was found to be higher with leguminous substrate than with non-leguminous ones.

Notizen: Results of pilot plant studies using an external-loop airlift bioreactor (170 l fermentation volume, liquid height-to-riser diameter: 27, loop-to-tower cross-section-area: 0.1225) have proven the relative merits of such a system in the bacitracin biosynthesis produced by the Bacillus licheniformis submerged aerobic cultivation.The results were compared to those obtained in a pilot-scale stirred-tank bioreactor with the same values of kLa. Excepting the aeration rate of 0.2 vvm, the fermentation process performed at 0.5 vvm and 1/0 vvm, respectively, unfolded similarly in the two fermentation devices with respect to the cell mass production, substrate utilization and bacitracin production during the fermentation process.In the riser section of the airlift bioreactor, the dissolved oxygen levels were higher, while in the downcomer section they were lower than those realized in the stirred tank bioreactor.Power requirements of the airlift fermenter were by 17-64% lower than those for a mechanically agitated system, depending on the aeration rates, which led to an important energy saving.Moreover, the lack of mechanical devices in the airlift system provides safety and a more gentle environment for the cultivation of microorganisms.

Notizen: The enzymatic esterification of octanoic acid with racemic butanol-2 was investigated. Esterifications of the acid were performed in a forced flow enzyme membrane reactor. The used membrane was prepared by a phase inversion process in polyamide-6 solution followed by the chemical immobilization of a lipase-catalyst.Influences of water content and pH were estimated. Their optimum values are equal to 0.5% w/w and pH 8. The reaction rate (at 303 K) of 5.1 × 10-5 mol/h·cm2 of the membrane area, and at least 85% enantiomeric excess in the produced ester mixture were obtained.The activity of immobilized lipase in the membrane process is about two times higher than that of the native lipase in the esterification performed in a tank reactor.

Notizen: Carbon and nitrogen influence the lipid accumulation and arachidonic acid production by Mortierella alpina CCF 185 cultivated at 28°C for 7 days on a rotary shaker. The fungus grown with glucose, starch or dextrin as the carbon source produced satisfactory amounts of lipid and arachidonic acid. The maximum arachidonic acid values were obtained on media with yeast extract or NaNO3 as the nitrogen source. The C/N ratio of 40:1 resulted in the highest yields of lipid and arachidonic acid with different amounts of NaNO3 concentration.

Notizen: The lipid accumulation, fatty acid composition and γ-linolenic acid (GLA) production by 28 strains belonging to Mucorales were investigated. The lipid content varied from 5 to 30% on dry biomass and the percentage of γ-linolenic acid in total intracellular lipid was in a range from 2.5 to 15.4% (w/w). The best yield of γ-linolenic acid (expressed as mg GLA per 1 g biomass) was found for Mucor mucedo CCF - 1384 (28.4) and Cunninghamella echinulata CCF - 103 (25.1).

Notizen: Acetobacter methanolicuswas grown on glucose in the presence of dinitrophenol (DNP) under carbon/energy-limited conditions. DNP affected both the growth yield and the growth rate (Dsh) at which the energy generation was shifted from a complete to an incomplete substrate oxidation by using the PQQ-linked glucose dehydrogenase. The more the growth yield was decreased, the higher both the DNP concentration and the growth rate became. At about 0.53 mM DNP, growth was completely stopped. Dsh decreased from 0.21h-1in the absence of DNP to 0.175 h-1and 0.075 h-1in the presence of 0.2 mM and 0.4 mM DNP, respectively. The experimental data are discussed in terms of the limitations in the generation of energy and some stress situations which are exerted by the presence of the uncoupler.

Notizen: The presence of dinitrophenol (DNP) during the chemostatic growth of Acetobacter methanolicuson glucose led to i) no significant increase in glucose dehydrogenase, ii) a decrease in the capacity to oxidize glucose by about 30%, not depending on the DNP concentration, and iii) a gradual decrease in the capacity to form gluconic acid, depending on the concentration of the uncoupler. Similar effects of DNP on Acetobacter methanolicuswere observed during the gluconic acid formation process. The loss in the capacity to form gluconic acid is indicated by a drop in the ATP concentration of the cells which cannot be counteracted by the ATP syntheses originating from the oxidation of gluconic acid and of glucose. ATP could be necessary for pumping protons out of the cells that were taken up together with gluconic acid and by the effect of DNP.

Notizen: The mechanism of catabolic repression is not yet fully understood. Oxygen seems to control the level of cytochrome in the in situ state. The level of glucose seems to control other enzymes; glucose by itself does not repress the cataboism. An unidentified product of glucose metabolism is believed to be involved. In bacterial cultures, there is convincing evidence that cyclic AMP is involved and this operates at the levels of gene trancription. In yeast, it is not clear. The level of CAMP is found to be reduced with catabolic repressed cells, but there is little evidence to conclude that CAMP acts at the transcription level [1]. There are results to indicate that it acts at the translational level or enzyme activation phase in yeast. In order to understand this mechanism, the bioenegetics of yeasts grown under catabolic repression is analyzed with the data available [2] and appended.

Notizen: Cell disruption studies for the extraction of HBsAg from a recombinant P. pastoris strain (r-HBsAg) were done using a bead mill disintegrator. Three sequential passages (4 min retention time each) were enough to disrupt the cells and extract most of the r-HBsAg and soluble proteins. An acid precipitation step was performed just after cell disruption to precipitate proteins together with the cell debris. Different precipitation pH values (2.5 to 6.0) were investigated. A pH value of 4.2 was selected as a compromise between recovery and improvement of specific activity. A 6 to 8-fold enhancement of the specific activity was obtained, having a r-HBsAg overall yield of about 80%. The influencing presence of a chaotropic salt (potassium thiocyanate) during the acid precipitation step was also studied.

Notizen: For the immobilization of spores of Penicillium raistrickii i 477 the formation of polyelectrolyte complexes using the sodium salt of cellulose sulphate as polyanion and poly-dimethyl-diallylammoniumchloride as polycation was used. Light and scanning electron microscopy have shown that during germination of spores the capsule walls do not cause effective limitations on hyphal growth and that there are no significant morphological changes of the mycelium detectable by an outgrowth of immobilized spores. By comparing the 15α-hydroxylation of 13-ethyl-gon-4-en-3,17-dione with free and encapsulated cells it was found that an increase of total dry biomass per immobilized system led to a higher product formation in relation to free cells.

Notizen: The kinetics of batch fermentation during the growth of S. cerevisiae ATCC 36859 was studied in various glucose/fructose mixtures. It was found that the growth is inhibited equally by glucose and fructose even though fructose is not consumed to any large extent by the yeast under the conditions tested here. The inhibition of growth by the substrate and ethanol is represented by linear equations. These equations were combined with the MONOD expression in order to formulate equations for the biomass growth, glucose and fructose consumption and ethanol production. Parameter estimates were obtained by fitting these equations to batch fermentation data and so developing models which indicate that the growth is completely inhibited when 62 g/l ethanol is produced by the yeast, while glucose consumption and ethanol production continue up to an ethanol concentration of 152 g/l. Products containing a high concentration of fructose are best produced by using a high initial biomass concentration.

Notizen: Optimization studies have been carried out for the production of L-lactic acid from the fermentation of whey by Lactobacillus casei. Two Statistical Designs, a full 24 Factorial Design and a full 32 Factorial Design, have been used to determine the most suitable values of the operational variables for obtaining the maximum lactic acid production rate. The variables selected for study were temperature, pH, lactose concentration, and inoculum concentration. Among them only temperature and pH were found to affect the response significantly. A second-order polynomial empirical model relating both the response (lactic acid production rate) and the variables was formulated. The maximum acid production rate was found when the values of pH and temperature were 5.4 and 38°C, respectively. All conclusions are restricted to the experimental range studied.

Notizen: The influence of different process kinetics on the course of phenol degradation has been studied as well as the influence of axial dispersion in the liquid phase on the reactor height with relatively large biofilm thickness in a conventional fluidized bed and air-lift bioreactor. The object of this was to achieve a high conversion of substrate in a device of real size in real process time. For calculating the mathematical model, the method of orthogonal collocation with the STIFF integration routine has been used.

Notizen: The killing/immunity interactions among killer strains of the genera Kluyveromyces, Hansenula and Saccharomyces from the Czechoslovak Collection of Yeasts were studied with the aim to find the strains with broad specificity and killer activity targeted against a range of undesirable wild yeasts causing stuck fermentations. Among 49 tested Kluyveromyces strains, five strains were found, and among 55 Hansenula strains, ten yeast strains were found with activity against a sensitive strain of Saccharomyces. Hansenula mrakii CCY 38-7-1 and Hansenula saturnus var. subsufficiens CCY 38-4-2 showed exceptional activity against the wine contaminants, Zygosaccharomyces bailii, as well as against pathogenic Candida species within a broad range of pH 2.9-5.1. Their potential biotechnological application is discussed.

Notizen: α-Galactosidase (E.C.3.2.1.22) from Penicillium janthinellum was purified by precipitation and fractionation with ammonium sulphate, cold acetone or ethanol, calcium phosphate gel, and column chromatographies on Sephadex G-100 and G-200. The enzyme was purified about 110.39-fold when Sephadex G-100 was used. α-Galactosidase exhibited the optimum pH and temperature at 4.5 and 60°C, respectively. The optimum enzyme stability was obtained at pH 3.5 for 24 h (at room temperature). The enzyme was found to be thermostable below 65°C up to 40 minutes and was gradually inactivated by increasing the temperature above this degree. The MICHAELIS constant was 0.55 mM for p-nitrophenyl-α-D-galactoside. The α-galactosidase activity was strongly inhibited by Hg++ and slightly activated by Mn++. The results show the possibility of producing a thermostable enzyme from a low-priced agricultural product, for instance, lupine.

Notizen: The cultivation of Acetobacter methanolicus on various substrates revealed that the respective maximum growth rates are obtained at an almost identical oxidative capacity of about 16 mmoles of oxygen g (biomass)-1·h-1 under conditions of energy generations by complete substrate oxidation. This is considered to be an indication that the energy production rate determined by the capacity of the respiratory chain limits the growth rate in this strain. However, with glucose and glycerol, for example, a further increase in the growth rate is observed accompanied by the generation of products (gluconic acid or dihydroxyacetone, respectively). The incomplete oxidation should play the role of an additional energy generation. The potential for this rate increase is looked for in a higher energy gain derived from reduction equivalents (PQQH2) in this periplasmic oxidation step in relation to the cytoplasmic reduction equivalents.

Notizen: In this paper, we consider a model for a chemostat in which two microbial species compete for a single rate-limiting nutrient, while one of the species feeds on another. Under certain simplifying hypotheses, such a chemostat can be described by a system of three nonlinear ordinary differential equations. A theoretical study is conducted to characterize the possible types of solutions. A limit cycle solution was obtained for some parametric values of the system indicating that coexistence of the two species is possible in a significant range of the operating parameters.

Notizen: Pretreated wheat straw was enzymatically hydrolyzed in 250-ml flasks using the culture filtrate of Trichoderma reesei QM-9414. The influence of the initial enzymatic activity in the liquid phase was studied. The unreacted core model was used to analyze the experimental data obtained at 40, 46 and 50°C. The model adequately describes the data for hydrolysis times lower than 10 h.

Notizen: This paper intends to focus the attention to characteristic features of microbial lignin degradation from the phenomenological point of view. Six fundamental principles are discussed under special consideration of white-rot fungi. The necessity of mycelial growth and the formation, secretion, and extracellular action of peroxidases are main requirements for a successful microbial attack on polymeric lignin.

Notizen: The ligninolytic fungus Phlebia radiata growing in a low-nitrogen medium with Avicel cellulose as the sole carbon source produced a full spectrum of celluloytic enzymes. Some properties of these enzymes were investigated during the growth of the fungal culture.

Notizen: The ligninolytic fungus Phlebia radiata growing in a low-nitrogen medium, with wheat bran as the sole carbon source, produces a wide spectrum of hemicellulolytic enzymes. During the growth of the fungal culture, some properties of these enzymes were investigated.

Notizen: The synthesis of extracellular serine proteinase of Lactococcus lactis was studied during the growth in a batch and a continuous culture on chemically defined media. In a batch culture the proteinase synthesis started during the exponential phase of growth and the highest proteinase concentrations were found at the end of the exponential and beginning of the stationary phase of growth. During the growth in a lactose-limited chemostat with amino acids as the sole source of nitrogen, the specific rate of proteinase synthesis was maximal at a μof 0.23 h-1. At higher growth rates the proteinase productin declined. The proteinase synthesis was dependent on the amino acid sources in the medium. In batch cultures of L. lactis grown on a chemically defined medium with amino acids, the proteinase production was increased four-fold compared to media containing casein or a tryptic digest of casein as the sole source of nitrogen. The inhibition of the rate of proteinase synthesis by casein and peptides was also observed during the growth in a chemostat. The addition of the dipeptide leucylproline (final concentration of 100 μM) to a lactose-limited continuous culture during the steady state (D = 0.23 h-1) resulted in a transient inhibition of the rate of proteinase synthesis. This suggested that exogenously supplied peptides control the regulation of proteinase synthesis of L. lactis.

Notizen: 515 microorganisms of the genus Bacillus which produce starch-degrading enzymes were isolated from natural environments in the course of a screening programme. Treating the Bacillus strains on agar plates with iodine reagent for 30 seconds led to the selection of clones with increased amylolytic activity. This methods is very convenient for the screening of large numbers of amylolytic strains.

Notizen: Presently, an urgent problem is the application of artificial intellect (AI) methods as a complex way of controlling and optimizing technological processes. The paper presents major principles of a bystage application of AI in biotechnology as knowledge extraction from data obtained by decomposing the sign space to clusters.

Notizen: In biotechnological processes, fundamental performances of microorganisms are used. The economy of these processes is essentially determined by the efficiency, velocity (productivity) and quality of the products. Therefore it is a permanent task and challenge for basic and biotechnological research to seek out measures for improving the actually attained parameters. The auxiliary substrate concept supplics an approach. It is based on the fact that chemo-organo-heterotrophic substrates differ in the carbon: energy ratio, thus, growth yield is limited in energy and/or reducing power. It says that, by simultaneous utilization of physiologically similar substrates (mixed substrates), the growth yield increases. The substrates are to combine in such a way that with their simultaneous utilization a minimum of carbon is dissimilated merely for the purpose of the generation of biologically useful energy and/or reducing power. Since all chemo-organo-heterotrophic substrates are more or less energy-deficient, an increase in growth efficiency can be expected if the individual substrates of the mixture are assimilated more efficiently than the respective substrates alone. This may result, for instance, from an immediate assimilation of a substrate (according to the “manner of finished part construction”).An increased growth rate is rather the rule than the exception in mixed substrate utilization.In product syntheses the substrates are, depending on the concrete product and metabolic pathway, either energy-excess or energy-excess or energy-deficient. or, in other words, the processes are energy-generating or energy-consuming, respectively. If this is responsible for discrepancies between the possible yields determined by the carbon metabolism and the experimentally obtained yields, the discrepancies should be able to be decreased and the yields increased by mixing substrates. The substrates are to choose and combine so that, due to simultaneous utilization, the product formation process becomes energy neutral.As a rule, the enhanced efficiency is accompanied by an increased velocity. This does not only apply to syntheses, but also to degradation (and detoxification) reactions. Even supposedly inert compounds or persistent substances can be activated by simultaneous (co-)metabolization of another (an auxiliary substrate, victim substrate or co-substrate) and converted at a considerable rate. It is of interest for syntheses of products but in particular for degradation and decontamination of harmful and waste products in the environment that the residual concentrations of the substrates are smaller than those achieved if the compounds of a mixture are metabolized separately.The auxiliary substrate concept has proven to be fruitful, both for theoretical and practical questions. It was practically already being used before it was formulated (mixed substrate utilization, cometabolism). However, an abundance of regulatory and energetic aspects are waiting to be investigated in more detail.

Notizen: The basic parameters were studied influencing the conversion of orbitol to sorbose by Gluconobacter oxydans(industrial strain from FARMAKON Co., Czechoslovakia). The most effective conversion in the stationary phase was reached at pH 5.0, no inhibitory effect of sorbitol in a concentration ranging from 20 to 200 g/l and a minimum inhibitory effect of the sorbose concentration up to 200 g/l were observed. According to the optimum conditions mentioned above the optimized course of the fed-batch cultivation was proposed. The final concentration of sorbose of 410 g/l was reached after 36 hours.

Notizen: The optimization task was performed using the gluconic acid synthesis by the Acetobacter methanolicusMB 58 strain. The microorganisms were grown continuously on methanol as the growth substrate. After finishing the growth process by the deficiency of N and P, the gluconic acid synthesis was started by adding glucose. The synthesis process was performed continuously. The oxygen transfer rate depended on the gluconic acid concentration. During the growth process, the oxygen transfer rate reached a value of about 13 g O2 · kg-1 · h-1using a 30-l glass fermenter equipped with a 6 blade stirrer and fully baffled. This rate declined to a value of between 2 and 5 g O2 · kg-1 · h-1 in the presence of gluconic acid concentrations above 150 g gluconic acid · kg-1medium. The yield (g gluconic acid · g-1glucose) depended on the gluconic acid concentration and amounted to y = 0.7 in relation to 150 g gluconic acid · kg-1medium and y = 0.8 in relation to 200 g · kg-1medium, respectively. The fermenters were coupled with ultrafiltration moduls (Fa. ROMICON and Fa. SARTORIUS). The biomass concentrations amounted from 5 to 40 g dry mass kg-1medium. The ultrafiltration modules retained the biomass within the fermentation system. A glucose solution (30 to 50 weight percent glucose) was continuously dosed into the fermenter. The retention time was chosen between 2 and 30 h. The gluconic acid synthesis rate reached values of up to 32 g gluconic acid · kg-1 · h-1. Within a range of up to 250 g gluconic acid · kg-1medium, the acid concentration had no influence on the enzyme activity.

Notizen: Cylinder-shaped sintered glass carriers were successfully used for immobilizing and cultivating cells of murine line L929. The process has been performed in a fixed-bed bioreactor (working volume of 150 ml) with perfusion and aeration of the medium (total volume of 3.5 l). The maximum cell density of 1.23 × 107cells/ml was achieved when the basal medium (MEM + 10% bovine serum) was enriched with glucose (up to 2 g/l) and L-glutamine (up to 4 mM). The carriers have proved to be nontoxic, mechanically stable and reusable.

Notizen: In order to optimize the thermophilic lactic acid fermentation on saccharose as the sole carbon source and improve the effectiveness of the process, alternative nitrogen sources were tested and a minimal broth composition was found. Of the alternative nitrogen sources, whey protein hydrolyzate (WPH) was the best; the broth composition was reduced from seven down to three items. Application of ammonium as a neutralizing agent instead of sodium hydroxide brought an important positive change.

Notizen: Dual or multiple parameter flow cytometric analysis is developing into a powerful method for characterizing microbial populations. The distinguishing of the populations only by assignment of size/shape measurements by scattered ligth renders as not satisfactory.To differentiate between the cells, the employment of a specific fluorescence marker is absolutely necessary. Methods are presented for the flow cytometric determination of DNA and the polymer poly-β-hydroxybutyrate (PHB) content in three different bacterial strains. The measurement of the 3β-hydroxysterol content enables the differentation between yeast and bacterial organisms in mixed microbial populations. Monitoring the ratio of live to dead bacterial cells in soil or water samples, e.g. in pure culture systems, is shown.

Notizen: The growth rate and the maximum cell concentration of methanotrophic bacteria are limited by the transfer of methane and oxygen to the culture fluid. The operation under moderate pressure results in an increase in driving force for the mass transfer of both nutrients and, therefore, in a large increase in the attainable biomass concentration.Our laboratory pressure fermenter with a volume of 12 litres operates under a system pressure of up to 0.5 MPa. In this reactor a maximum productivity of 6 g biomass/lh is achieved. However, operating under moderate system pressure and exhaust gas recycling has also disadvantages because the concentrations of the gas phase components may inhibit the growth process.From the results of the laboratory fermenter we have developed kinetic models of the influence of dissolved oxygen and carbon dioxide on the specific growth rate of the methanotrophic strain GB 25. These models are the basis for processing under increased system pressure and exhaust gas recycling.

Notizen: A spontaneous association of Cellulomomas sp. with another bacterial strain was studied for its capabilities for single cell protein (SCP) production from bagasse pith. The associated strain was identified as Pseudomonas sp. and further characterized for its physiological properties. The effect of the initial proportions of both strains, the way of propagation, and the effect of pH on the growth of the mixed culture on bagasse pith was studied. Separate propagation of both strains before the fermentation step (“controlled mixed culture”), a range of proportions Cellulomonas-Pseudomonas from 4:1 to 100: 1, and pH 7.0, were found to be the most appropriate conditions of growth. A mutualistic symbiotic relationship was demonstrated to take place between both strains during the mixed growth on bagasse pith, the Cellulomonas supplying the carbon source (glucose produced from bagasse degradation) to the Pseudomonas, and the latter producing the vitamin supplements necessary for the Cellulomonas growth, allowing the growth of the mixed culture in a minimal medium, without any growth factor supplement. Fed-batch cultivation of the mixed culture on this substrate was successful, giving rise to high biomass production (19.4 g/l), thus increasing the productivity of the system. Due to its improved productivity, high biomass production, inexpensiveness of the culture medium, (without any vitamin supplement), and good stability, this culture presents economical advantages and constitutes an attractive choice for lignocellulosic substrate utilization.

Notizen: A mathematical model, DH = 1/k(10-2ΔpH - 1), between the pH-drop (ΔpH) and degree of hydrolysis (DH) of an enzymatic modification of casein was developed to assess the DH in a packed-bed column reactor by directly monitoring the pH value of the modified protein system. It was demonstrated that the linear DH range and the k value of the equation were dependent on the reactor type and the specificity of the proteolytic enzymes immobilized on chitin used in the present study, but no effect of the substrate casein concentration on the linear DH range was observed. Since DH and ΔpH values of the modified casein correlated with the flow rate in a packed-bed column reactor, it was suggested that the DH value, in a considerably wide range of casein modification with a certain immobilized protease in a column reactor, could be controlled by adjusting the flow rate of the substrate and monitored by a pH-meter. This relationship might be used as a basis for scale-up and long-term operation of enzymatic modification of proteins by immobilized protease in a column reactor.

Notizen: The expression of the human Growth Hormone (hGH) in transgenic mice is accompanied by health afflictions and structural changes in several organs and tissues. A macroscopic and light microscopic study was conducted to examine the morphological alterations related to the exposure of endogenously expressed hGH. Although many transgenic mice were under cachectic status, their body and organ weights were significantly higher than those of the controls matched. Kidney, liver and female genital organs were massively damaged.The most common findings in these organs were glomeruli hyalinosis and glomerulosclerosis in the kidneys accompanied by a varying degree of segmental sclerosis and necrosis. Tubuli dilatation was observed with hyaline casts and atrophied epithelium as well as interstitial fibrosis with mononuclear infiltrate. In the liver the hepatocytes were pleomorphic and exhibited vacuolar degeneration. Intranuclear lipid droplets were also found. Individual necrosis, mononuclear infiltrate and nuclear pseudoinclusions were also detected. The uterus exhibited cystic glandular hyperplasia and ovaries were observed to have several, large foamy cells as well as stromal infiltration of adipose cells. Other changes were found in the heart, the spleen and the salivary glands. A possible role of GH and/or the Insulin-like Growth Factor-I is suggested according to the morphological changes found. The similarity to kidney changes with human diabetic glomerulosclerosis was noticed.

Notizen: The tissue specificity of the expression of the hepatitis B surface antigen (HBsAg) in transgenic mice was studied. Northern blot hybridization and electron microscopy of various tissues revealed the higher HBsAg transcription levels confined to the liver and kidney, and to a lesser extent to the spleen and intestines. In electron microscopic studies we found HBsAg particles in the serum of transgenic animals to be positive by ELISA to HBsAg. The expression of the transgene was localized in situ in the ovary, liver, kidney, and spleen of transgenic mice, employing a polyclonal antiserum directed against the HBsAg and conjugated with protein A-gold. Surprisingly, F1 transgenic females from the CB-104 line, expressing HBsAg in the serum, showed impaired fertility, although the ovarian function was not diminished. Normal off-spring were obtained after cross embryo transfer between transgenic (Tg) females to non-transgenic (Ntg) recipients or from Ntg embryos transferred to Tg recipients. We speculate that this phenomenon could be related to a disruption on a gene(s) somehow involved in the reproductive performance of the transgenic females.

Notizen: Fifteen trace elements have been tested to determine the requirements for the growth of Phellinus pachypholeus Pat. The fungus requires in ppm, Fe: 10, Zn: 10-100, Mn: 1.0, Cu: 1.0, Mo: 1.0, B: 10.0-100. It does not require Ca, Pb, Br, I, Cr, Hg, W, Li or Cd. Concentrations higher than the optimum were progressively inhibitory for its growth.

Notizen: Several types of high organic matter pollutants containing (COD-range: 3-50 kg · m-3) industrial waste waters were treated in laboratory scale (1.2-23 dm3) sludge blanket (UASB) and UASB-fixed bed hybrid (UBF) reactors. In most cases higher than 80% of COD-removal efficiency has been attained. The CO2 content of the biogas developed was mainly influenced by the neutralization (base to acid) ratio related to feed pH.Cell immobilization by granule formation was considered as a change in microbial population: enrichment and aggregate formation of Methanotrix-like filamentous microorganisms. Based on physiological and physical indexes of microbial selection and with regard to the different sensitivities of microorganisms to substrate inhibition, a new start-up method was developed for rapid (40-45 days) granulation of raw digested sludge.

Notizen: Micro-organisms have often been considered for the production of oils and fats as an alternative to agricultural commodities. However, with the continuing low cost of agricultural production of oil-seeds, biotechnology has little to offer in the way of competition against such items as soybean oil, groundnut oil, and even polyunsaturated oil such as sunflower oil even though good facsimiles of these oils could be produced. It is now clear that if we are to use microorganisms to produce lipids, i.e. Single Cell Oil, then these must be highly specific ones which are currently expensive to obtain from agricultural sources. In particular, the possible production of a cocoa-butter substitute using mutated yeast cells is reviewed here as well as the production of highly polyunsaturated fatty acids (PUFAs) using various species of mould. With regard to producing a cocoa-butter equivalent fat, it is necessary to identify not only a cheap carbon source on which the yeast may grow (this is now considered likely to be lactose arising from whey) as well as deriving a mutant strain of the yeast which will accumulate large amounts of stearic acid within the oil. The recent work carried out in The Netherlands and New Zealand to achieve these goals is described. With regard to polyunsaturated fatty acid production, various prospects exist and indeed, the commercial production of one acid, gamma-linolenic acid, is now being produced commercially in both the U.K. and Japan. The background work leading to this product is described and opportunities for other PUFAs being produced biotechnologically are discussed.

Notizen: Bradyrhizobium sp. isolated from the root nodules of a leguminous shrub, Crotalaria retusa L., produced a high amount of indole acetic acid (IAA) from tryptophan in the culture. The bacteria preferred D-isomer to the DL- or L-isomer of tryptophan for the IAA production. The IAA production could be increased up to 153.6% over control by supplementing the medium with arabinose (0.5%), ZnSO4(0.01 μg/ml), KNO3 (0.1%), thiamine-HCl (0.01 μg/ml) and EDTA (5 μg/ml).The possible role of the rhizobial production of IAA with the rhizobia-legume symbiosis is discussed.

Notizen: The production of genetically engineered antibodies in Escherichia coli is now possible. The resulting fragments are completely functional and have antigen binding constants industinguishable from the natural antibody. This article summarizes the biochemical basis of this newly developed technology and the properties of the resulting fragments. It is likely that this technology will have an important role in antibody production for technical, medical and research uses. Screening of E. coli libraries may mount a challenge to traditional antibody production methods.

Notizen: Two isoenzymes of chorismate mutase (EC 5.4.99.5), designated as CM-1 and CM-2, were isolated and partially purified from suspension-cultured cells of Ruta gravelens by DEAE-sephacel chromatography and gel filtration. 60-72% of the total activity measured after DEAE-sephacel chromatography were obtained as CM-1 and 28-40% were CM-2 activity. CM-1 was inhibited by phenylalanine (K1 = 4 · 10-6 M) and tyrosine (K1 = 8. 10-6M) and activated by tryptophan. In contrast, CM-2 was not influenced by these three amino acids. The molecular weights estimated by gel filtration on SEPHADEX G-150 were 56000 for CM-1 and 45000 for CM-2, respectively. Both isoenzymes were stable at -20°C, but exhibited different behaviour during thermal inactivation and different optima of reaction temperature. CM-1 catalysed the reaction at a pH optimum of pH 7.8 and CM-2 showed a broad optimum between 6-10. The Km-values for chorismic acid were determined to be 1.1 mM for CM-1 and 0.5 mM for CM-2. The isoenzymes showed different behaviour to inhibitors of sulfhydryl groups. There were no differences in all parameters of chorismate mutase examined for two various cell lines of Ruta graveolens.

Notizen: The kinetics of D-glucose isomerization to D-fructose by an original whole-cell immobilized biocatalyst preparation based on Streptomyces thermovulgaris (strain 127) have been studied under various process conditions, substrate concentration, particle size. Two versions of different activity were applied. For the biocatalyst of moderate activity the kinetic constants in the MICHAELIS -MENTEN equation for reversible reaction were determined. Effectiveness factors for both preparations were calculated and compared with other reported data.

Notizen: The occurence of multiple forms of alcohol dehydrogenase (ADH) in methylotrophic yeasts is known from the literture. But no systematic work has been done to characterize these enzymes in detail. The aim of this work was to establish a suitable electrophoretic method for visualization of the ADH-patterns of these organisms. It was found that the recovery of the enzyme activity during polyacrylamide gel electrophoresis (PAGE) depends on the composition of the gel buffer. The ADH of five different methylotrophic yeasts from the genera Candida, Pichia and Hansenula were analyzed. Every investigated organism shows rather complex ADH-patterns.

Notizen: Pseudomonas sp., strain S ATCC 43 388 utilizes α-santonin by inducible enzyme system measurable by oxygen uptake. Cells grown on acetate or benzoate show negligible oxygen consumption with α-santonin. However, glucose grown cells show evidence of a rapid induction of santonin utilizing enzyme system indicating the implication of glucose or its metabolites in the regulation of degradation of santonin. As a consequence, growth of strain S on mixtures of glucose and α-santonin occurs at rates higher than on either of the substrates alone. Mutants with lesion in the glucose metabolism, independent of α-santonin degradation, fail to exhibit higher growth rates with the binary substrates. The results infer simultaneous metabolism of substrates.

Notizen: A new metabolite, identical with dehydroaltenusin was isolated from a strain Talaromyces flavus B 5 which was selected from parental strain 51 C/I. Metabolite inhibited the growth of wooddamaging fungi, especially Ciadosporium sphaerospermum and P388 leukemid cells.

Notizen: Laccase (E.C. 1.10.3.2) is slowly inhibited by lower fatty acids in a reversible reaction. The degree of inhibition depends on kind and concentration of the fatty acid, but not on the concentration of the enzyme itself. The degree of inhibition increases with the chain length of the fatty acids. The maximum inhibition was found with butyric acid.

Notizen: We studied some mechanisms of cellobiase formation in Asp. Japonicus VKM F-2092 aiming at the subsequent development of controlled cultivation to produce the enzyme.Formation of cellobiase was found to be of noninducible constitutive character. The enzyme was predominantly localized in the cytosole and the periplasm, its minor portion being cell-wall bound.The release of the enzyme into the medium was due to autolytic processes.The two-phaseness of cellobiase formation in Asp. Japonicus grown on a mineral medium with 0.5% glucose was shown to be determined by the following mechanisms: 1Catabolic repression. We established glucose concentrations causing the repression and found it to be dependent on carbon sources in the growth medium.2Catabolic inhibition. Cellobiase activity was found to be inhibited by assumed glucose metabolites in the presence of nitrate nitrogen in the medium..Practical recommendations to optimize the process of cellobiase production by Asp. Japonicus are given.

Notizen: The solubilization of silicates was investigated using kaolin and quartz sand as model substances. The mineral solubilization was studied in the concentration of solubilized Si and Al. The chemical leaching of the silicates was carried out using inorganic and organic acids as well as sodium hydroxide. The process was more effective in the alkine than in the acid pH range. In the acid medium, oxalic acid showed maximum acidity and a tendency to form complex structures, especially with aluminium, and was most effective in leaching.The microbiological influence on solubilization reactions was tested using a number of microorganisms among them acid, alkali and slime-forming species. The highest leaching activity was observed in the case of Thiobacillus thiooxidans, whereas the heterotrophic microorganisms (among them Bacillus mucilaginosus) did not exercise a sollubilizing effect on the silicates.X-ray phase analysis of leached kaolin samples did not show any differences from the non-leached mineral.

Notizen: An effect of the Au(III) energy dependent concentration has been discovered by living Chlorella cells. The process is most intensive within the alkaline interval of pH, fading away in the dark, and is suppressed in the presence of arsenate (C ≧ 1 μM), fluorides (C ≧ 0.01 mM), sodium azide (1 mM), DCCD (10 μM), 2, 4-dinitrophenol (0.1 mM). In the dark the process is stimulated by ATP (but not by ADP, or AMP). ATP also neutralizes NaN3 effect, but not that of DNP. An energy dependent Au(III) concentration is also observed for other green, blue-green, and, red singlecell algae.

Notizen: Solid state fermentation of canola meal has been carried out for the reduction of its phytic acid content using the following microorganisms: Rhizopus oligosporus NRRL 2990, Aspergillus niger NRC 5765 and NRC 401 121, Aspergillus ficuum NRRL 3135 and a wild Saccharomyces cerevisiae strain.The results showed that all these microorganisms can be used for the reduction of the phytic acid content in the tested material. A. ficuum which completely hydrolyzed the phytic acid in 48 hours was the most efficient.Buffered systems, aeration and an increase in inoculum concentration caused faster and higher reduction of phytic acid content in canola meal.