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  • 1
    Electronic Resource
    Electronic Resource
    Mathematical modeling of production of microbial lipids (1991)
    Springer
    Bioprocess and biosystems engineering 6 (1991), S. 227-234 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract As a part of the investigations on the microbial lipid production using the yeast Rhodotorula gracilis, CFR-1, kinetics of the biomass synthesis has been studied using shake flask experiments. Using a medium containing a carbon to nitrogen ratio of 70∶1, the rates of biomass production were followed at different initial substrate concentrations in the range of 20–100 kg/m3. A logistic model was found to be reasonably adequate to describe the kinetics of the growth of biomass; the maximum specific growth rate of 0.105 h−1 was applicable for substrate concentrations less than 60 kg/m3, which gave reasonable agreement between predicted and actual biomass concentration values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369716
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  • 2
    Electronic Resource
    Electronic Resource
    Mathematical modeling of production of microbial lipids (1991)
    Springer
    Bioprocess and biosystems engineering 6 (1991), S. 241-248 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In the microbial lipid production system using the yeast Rhodotorula gracilis, CFR-1, kinetics of lipid accumulation and substrate utilisation at initial substrate concentrations in the range of 20–100 kg/m3 were investigated using shake flask experiments. A mathematical representation based on logistic model for biomass and Luedeking-Piret model for lipid accumulation gave reasonably good agreement between the theoretical and experimental values for substrate concentration less than 60 kg/m3. The kinetic expressions and parameters obtained through shake flask studies were directly applied to experiments in the laboratory fermentors also and the models were found to hold good for the prediction of the change of biomass, product as well as substrate with time. The attainment of a saturation in the intracellular lipid accumulation with time, however, was not predicted by the model which was shown to be an inherent feature of the Luedeking-Piret model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369553
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  • 3
    Electronic Resource
    Electronic Resource
    Gaseous concentration gradients in tray type solid state fermentors — Effect on yields and productivities (1992)
    Springer
    Bioprocess and biosystems engineering 8 (1992), S. 67-72 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In aerobic solid state fermentation systems, interaction of mass transfer effects with bioreaction plays an important role on the yields and productivities of the bioreactors. Experimental observations on the oxygen and carbon dioxide concentration gradients in a tray type solid state fermentation system are reported in this paper. Steep gradients are experienced in deep beds making large portions of the bioreactor ineffective. The results are useful in the design of the bioreactor in terms of efficient mass transfer as well as critical thickness of the substrate bed to be used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369266
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation of the utilization of 4-hydroxybenzoate and 4-hydroxycinnamate in batch and continuous cultures of Pseudomonas testosteroni (1979)
    Springer
    Archives of microbiology 120 (1979), S. 97-103 
    Details
    ISSN: 1432-072X
    Keywords: Aromatic substrates ; Regulation ; Alternating induction and repression ; Continuous culture ; Pseudomonas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pseudomonas testosteroni metabolized 4-hydroxycinnamate by an initial cleavage of the side chain to yield acetate and the aromatic moiety, 4-hydroxybenzaldehyde. The latter was further oxidized via 4-hydroxybenzoate to protocatechuate, which underwent meta cleavage. During growth of the organism on 4-hydroxycinnamate, the $$Q_{O_2 } ^{\max } $$ for acetate showed an undulating pattern, which was attributed to alternating induction and repression of enzymes involved in the oxidation of acetate. Repression was caused either by 4-hydroxybenzoate or by its later metabolites, formate and pyruvate. In batch culture, P. testosteroni oxidized mixtures of 4-hydroxybenzoate and 4-hydroxycinnamate in a diauxic pattern. The capacity to oxidize 4-hydroxycinnamate appeared in the cells before 4-hydroxybenzoate was exhausted, indicating that the enzymes catalysing the conversion of 4-hydroxycinnamate into 4-hydroxybenzoate. were induced despite the presence of 4-hydroxybenzoate. The induction of these early enzymes of 4-hydroxycinnamate catabolism started when the molar concentration ratio of 4-hydroxybenzoate to 4-hydroxycinnamate fell below a value of 0.3. In continuous culture of P. testosteroni on a mixture of 4-hydroxybenzoate and 4-hydroxycinnamate, both substrates were almost completely utilized up to a dilution rate of about 0.5/h. At higher dilution rates, 4-hydroxycinnamate was decreasingly utilized so that eventually at a dilution rate of 0.74/h, its effluent concentration equalled its influent concentration. At D M, a utilization ratio of 1.23 in favour of 4-hydroxybenzoate was found to become established in the culture. The $$Q_{O_2 } ^{\max } $$ of the cells for acetate was maximal at a dilution rate of 0.38/h and decreased before 4-hydroxycinnamate utilization was at its peak at 0.59/h. This suggested that it was mainly the aromatic moiety of 4-hydroxycinnamate which was metabolized at high dilution rates. The failure to utilize acetate at high dilution rates was apparently due to the repression of its catabolic enzymes by later metabolites of 4-hydroxybenzoate and to the relatively low concentration of acetate in the fermenter. This low concentration, due to the continuous washout of acetate, prevented it from relieving the repression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00409095
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  • 5
    Electronic Resource
    Electronic Resource
    Comparative studies on the metabolism of aniline and chloroanilines by Pseudomonas multivorans strain An 1 (1979)
    Springer
    Applied microbiology and biotechnology 7 (1979), S. 181-189 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Pseudomonas multivorans strain An 1 used aniline but not chloroanilines as the sole source of carbon and energy for growth. The aniline-adapted cells, however, were able to oxygenate chloroanilines. Relative oxygenation rates for aniline, 2-chloroaniline, 3-chloroaniline, 4-chloroaniline, and 3,4-dichloroaniline were 100, 46, 66, 20, and 3%, respectively. The first intermediates in the metabolism of chloroanilines were chlorocatechols. 3-Chlorocatechol accumulated during growth of the organism in the presence of 2-chloroaniline, whereas 4-chlorocatechol was an intermediate metabolite of 3-chloroaniline and 4-chloroaniline. Chloroanilines were able to induce synthesis of the aniline oxygenating enzyme system of Pseudomonas multivorans strain An 1. In continuous culture experiments, induction of this enzyme system appeared to depend on cell density, concentration, toxicity, and pK-values of aniline or chloroanilines. Studies with 14C-labelled 3-chloroaniline and 4-chloroaniline showed that the turnover of chloroanilines did not cease with the formation of chlorocatechols, because radioactivity was detected in the CO2 released and in bacterial cell components. The results suggest that the turnover of chloroanilines is due to metabolism rather than to cometabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00505024
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation of stearoyl lactic acid ester catalyzed by lipases from Rhizomucor miehei and porcine pancreas optimization using response surface methodology (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 579-584 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The esterification reaction between stearic acid and lactic acid using Rhizomucor miehei lipase and porcine pancreas lipase was optimized for maximum esterification using response surface methodology. The formation of the ester was found to depend on three parameters namely enzyme/substrate ratio, lactic acid (stearic acid) concentration and incubation period. The maximum esterification predicted by theoretical equations for both lipases matched well with the observed experimental values. In the case of R. miehei lipase, stearoyl lactic acid ester formation was found to increase with incubation period and lactic acid (stearic acid) concentrations with maximum esterification of 26.9% at an enzyme/substrate (E/S) ratio of 125 g mol−1. In the case of porcine pancreas lipase, esterification showed a steady increase with increase in incubation period and lactic acid (stearic acid) concentration independent of the E/S ratios employed. In the case of PPL, a maximum esterification of 18.9% was observed at an E/S ratio of 25 g mol−1 at a lactic acid (stearic acid) concentration of 0.09 M after an incubation period of 72 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051563
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  • 7
    Electronic Resource
    Electronic Resource
    Study on the production of 6-pentyl-α-pyrone using two methods of fermentation (2000)
    Springer
    Applied microbiology and biotechnology 53 (2000), S. 610-612 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The lactone 6-pentyl-α-pyrone has a characteristic coconut aroma and is produced by Trichoderma species. A study on the fermentative production of 6-pentyl-α-pyrone in both surface and submerged conditions by Trichoderma harzianum was carried out. Maximum concentrations of 455 mg/l and 167 mg/l after 96 h and 48 h of fermentation in surface and submerged conditions, respectively, were obtained without using any additional recovery operations. The resultant yields are higher than those previously reported in the literature, which may be attributable to strain characteristics in combination with the choice of fermentation conditions employed in the present study. Enough scope exists for further improvement in the yields by optimizing the cultural and nutritional parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051665
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  • 8
    Electronic Resource
    Electronic Resource
    Enzymatic synthesis of isoamyl butyrate using immobilized Rhizomucor miehei lipase in non-aqueous media (2000)
    Springer
    Journal of industrial microbiology and biotechnology 25 (2000), S. 147-154 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: enzymatic synthesis; esterification; flavor ester; isoamyl butyrate; lipase; solvent-free synthesis; Rhizomucor miehei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Isoamyl butyrate, an important fruity flavor ester, was synthesized using Rhizomucor miehei lipase immobilized on a weak anion exchange resin (Lipozyme IM-20) by the esterification of isoamyl alcohol and butyric acid. The effects of various reaction parameters such as substrate and enzyme concentrations, substrate molar ratio, temperature and incubation time have been investigated. Yields above 90% were obtained with substrate concentrations as high as 2.0 M. No evidence of enzyme inhibition by butyric acid was present up to 1.0 M concentration. Acid inhibition and, to a small extent, alcohol inhibition were evident above 1.0 M substrate concentration. Conversions reached a saturation value by the end of 24–48 h of incubation due to the accumulation of the water of reaction. The equilibrium was successfully pushed forward towards esterification by removing the accumulated water using a molecular sieve.Journal of Industrial Microbiology & Biotechnology (2000) 25, 147–154.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.7000045
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  • 9
    Electronic Resource
    Electronic Resource
    Scale up studies for the production of biosurfactant in packed column bioreactor (2000)
    Springer
    Bioprocess engineering 22 (2000), S. 95-99 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Biosurfactants capable of emulsifying pesticides have great potential to assist in microbial degradation of the pesticides. Solid State Fermentation (SSF) due to several advantages, is one of the efficient ways of producing these surfactants and seldom receives attention for commercial exploitation. In this study, a packed column bioreactor with wheat bran as the raw material and Bacillus subtilis has been used to produce a biosurfactant specific to disperse Fenthion, an organophosphrous pesticide. The emulsifier activity (EA) and surface tension from the packed column bioreactor were compared with flask fermentation experiments, which served as control. Airflow rate in the packed column bioreactor was varied from 10–20 l/min. Maximum EA and minimum surface tension occurred at airflow rate of 20 l/min. Peak EA in the control was 1.2 at 29 h while it was 1.9 in the bioreactor. The least surface tension of 24 dynes/cm was noticed at 54 h in the bioreactor, which was 33% better than the control at the same time period. The results indicate that the packed column bioreactor can become a more acceptable solid state fermentation system for commercial exploitation of Fenthion specific biosurfactant production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004490050017
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  • 10
    Electronic Resource
    Electronic Resource
    Multiple continuous stirred tank reactors VS. Batch reactors — some design considerations (1979)
    Springer
    Biotechnology letters 1 (1979), S. 139-144 
    Details
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A comparison of the performance of single CSTR and 2-CSTR systems against a stirred batch immobilized enzyme (IME) reactor has been made. When the downtimes in a batch reactor are not too small, the 2-CSTR system may become attractive and therefore a proper consideration should be given to the 2-CSTR system particularly when the application of a plug flow reactor is not practicable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01386713
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