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  • 1
    Electronic Resource
    Electronic Resource
    Use of cheese whey as a substrate to produce manganese peroxidase by Bjerkandera sp BOS55 (1999)
    Springer
    Journal of industrial microbiology and biotechnology 23 (1999), S. 86-90 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: cheese whey; manganese peroxidase; Bjerkandera sp; white-rot fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Manganese peroxidase, MnP, is one of the major ligninolytic enzymes produced by a number of white-rot fungi. The ability of this enzyme to degrade lignin by the fungus Bjerkanderasp BOS55 has opened its application to related bioprocesses such as recalcitrant-compound degradation and effluent decolorization. The medium reported to induce MnP production is composed of chemical grade reagents, all with relatively high costs for application to detoxification purposes. The use of inexpensive sources for MnP production can bring its implementation closer. For this purpose, dairy residues from cheese processing were considered. MnP production obtained using crude whey as the sole substrate reached appreciable levels, around 190 U L−1, values comparable to those found with synthetic media (between 175–250 U L−1). Thus, this cheese-processing byproduct can be used as an inexpensive alternative for the large-scale production of MnP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900691
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  • 2
    Electronic Resource
    Electronic Resource
    A pulsing device for packed-bed bioreactors: I. Hydrodynamic behaviour (1994)
    Springer
    Bioprocess and biosystems engineering 10 (1994), S. 61-73 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper describes a new pulsing device which permits the insertion in pulsing form of a liquid phase fed into an equipment where a microbial or enzymatic transformation occurs. It also analyzes the modifications of the flow model caused by the pulsation generated by means of three kinds of pulsators: A hydropneumatic pulsator, a selfpropelled pulsator and a newly designed elastic membrane pulsator. The hydrodynamic behaviour of a packed-bed column, to which each of these pulsators has been connected is compared with the correspondent system without pulsation. The flow model is determined by the study of the curves of residence times distribution, obtained by using a stimulus-response technique. A computer programme has been used to determine the axial dispersion coefficients from the response curves. In all cases we worked within a wide range of Re p(10–215). The pneumatic pulsing device causes a backmixing in the system due to the alternative movement that communicates to the fluid contained in the column. The application of the pulsation by means of the selfpropelled injector or the elastic membrane pulsator reduces the axial dispersion coefficient in regard to those corresponding to the system without pulsation, a fact which becomes even more significant when operating at high flow velocities. For the study of the hydraulic model of the pulsing system of elastic membrane we worked under different conditions in order to determine the effect of the particle's diameter, the viscosity, and the frequency of pulsation. At the same frequency at which the Re pincreases, the axial dispersion coefficient also increases, following in all cases an almost linear tendency. For the same Re p, the dispersion coefficient decreases when the particle diameter increases. On the other hand, the dispersion coefficients obtained for a fluid of a viscosity of 2 cp are, in some cases, up to 3 times higher than the corresponding values for water. All the results indicate that the new pulsator is specially applicable to reactors which, as in many biological transformations, present inhibitory problems by the product, or, in general, to those reactions that require that the flow model in the reactor be a plug flow model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393388
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  • 3
    Electronic Resource
    Electronic Resource
    A pulsing device for packed-bed bioreactors: II. Application to alcoholic fermentation (1994)
    Springer
    Bioprocess and biosystems engineering 10 (1994), S. 75-81 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract When the immobilized cells are employed in packed-bed bioreactors several problems appear. To overcome these drawbacks, a new bioreactor based on the use of pulsed systems was developed [1]. In this work, we study the glucose fermentation by immobilized Saccharomyces cerevisiae in a packed-bed bioreactor. A comparative study was then carried out for continuous fermentation in two packed-bed bioreactors, one of them with pulsed flow. The determination of the axial dispersion coefficients indicates that by introducing the pulsation, the hydraulic behaviour is closer to the plug flow model. In both cases, the residence time tested varied from 0.8 to 2.6 h. A higher ethanol concentration and productivity (increases up to 16%) were achieved with the pulsated reactors. The volumes occupied by the CO2 were 5.22% and 9.45% for fermentation with/without pulsation respectively. An activity test of the particles from the different sections revealed that the concentration and viability of bioparticles from the two bioreactors are similar. From the results we conclude that the improvements of the process are attributable to a mechanical effect rather than to physiological changes of microorganisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393389
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  • 4
    Electronic Resource
    Electronic Resource
    Hydraulic model of a gas-lift bioreactor with flocculating yeast (1995)
    Springer
    Bioprocess and biosystems engineering 12 (1995), S. 269-272 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The hydraulic model of a gas lift bioreactor, during a continuous alcoholic fermentation by using a strongly flocculating yeast, is analysed. Sucrose at two different concentrations (50 and 100 g/l) was used as substrate and the dilution rate for all the experiments was 1 h−1. The biomass concentrations were between 85 and 110 g dry weight/1. A stimulus response technique was used to obtain the Residence Time Distribution curves, a pulse of a lactose solution being used as the tracer. Mixing time was determined by means of the response to a pulse of an acid tracer. These experiments were carried out by using an on-line data-acquisition system. The bioreactor behaviour is completely homogeneous, except for high substrate and biomass concentrations. A two parameters combined model is necessary, in this case, to fit the experimental data. Mixing times are very low, in the order of 10 seconds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369501
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  • 5
    Electronic Resource
    Electronic Resource
    Knowledge based control applied to fixed bed pulsed bioreactors (1996)
    Springer
    Bioprocess and biosystems engineering 14 (1996), S. 113-118 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In this work, an expert system was developed and applied for on-line control and supervision of ethanolic fermentation by immobilized Saccharomyces cerevisiae in a fixed-bed pulsed bioreactor of 1.2 l of working volume. A number of experiments with different substrate concentrations (75, 100, 150 and 200 g/l) and hydraulic residence times (2.4, 1.2 and 0.8 h) were carried out. Knowledge-based computer-aided supervision of this process involves accurate on-line measurement of the relevant process variables (temperature, pH, flow rate, carbon dioxide production, etc.). Carbon dioxide production was used for the estimation of the ethanol productivity. The analysis of the measured data allowed to detect states or trends that may be indicative of process or system failures, providing advices and/or alarms. The results showed the reliability of the control system. In previous works, it was proven that pulsing the feed stream highly improves the productivity of fermentation processes carried out in fixed-bed bioreactors [14, 15, 16]. The amplitude and frequency of the pulsation, which is a key factor in the performance of a pulsed feed bioreactor [13], was selected by the control system by using an algorithm allowing the ethanol productivity to be optimized. The pulsation frequency which maximizes the ethanol productivity, presents a high dependency on the hydraulic residence time and the feeding substrate concentration. When increasing the substrate concentration the optimum pulsation frequency also increases; when increasing the hydraulic residence time the optimum pulsation frequency decreases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369427
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  • 6
    Electronic Resource
    Electronic Resource
    Oxalic acid production by Aspergillus niger (1998)
    Springer
    Bioprocess engineering 19 (1998), S. 247-252 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Aspergillus niger is able to produce a quite high concentration of oxalic acid using sucrose as carbon and energy source. Operating at pH higher than 6 and an enriched N and P medium is necessary in order to conduct the fermentation towards oxalic acid production. A pH shift technique, operating at acid pH in the first two days and then setting pH to 6, allowed the productivity to slightly increase in shaking flasks cultures up to 3.0 kg/m3 · d, with a final oxalic acid concentration of 29 kg/m3. When operating at more controlled conditions, in a stirred tank, both productivity and oxalic acid concentration were improved (4.1 kg/m3 · d and 33.8 kg/m3, respectively). However the main drawback of this fermentation is the low yield attained (about 0.3 kg oxalic acid/kg sucrose) because most of glucose, resulting from the hydrolysis of sucrose by the extracellular enzymes secreted at the beginning of the fermentation, is very quickly oxidised to gluconic acid, a process which is favoured at a pH close to 6. Milk whey was proved to be a very good substrate as it allows oxalic acid to be produced with a similar productivity (2.5 kg/m3 · d in shaking flasks) giving excellent yields of almost 0.6 kg oxalic acid/kg lactose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009017
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  • 7
    Electronic Resource
    Electronic Resource
    Oxalic acid production by Aspergillus niger (1998)
    Springer
    Bioprocess engineering 19 (1998), S. 337-342 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Oxalic acid is formed by Aspergillus niger at nearly neutral pH values. In this study the applicability of milk whey as a carbon source was investigated, both in shaking flask experiments and in a stirred tank reactor. The influence of pH on oxalic acid formation showed that the maximum production rate and higher concentration of the product are observed at pH 6. At pH 7 the same production rate was obtained although at a lower oxalic acid concentration. The process was shown to be inhibited by product from an oxalic acid concentration of about 10 kg/m3 and its behaviour was fitted by Luong's equation. In a 10-dm3 strirred tank ferment the stirrer speed was varied in a range from 100 to 600 rpm. At values between 200 and 400 rpm, maximum production rates of oxalic acid of 6.8 kg/m3·d and 6.5 kg/m3·d were reached, respec-tively. A final concentration of 41.4 kg oxalic acid/m3 was reached operating at 400 rpm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009022
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  • 8
    Electronic Resource
    Electronic Resource
    Knowledge based control applied to fixed bed pulsed bioreactors (1996)
    Springer
    Bioprocess engineering 14 (1996), S. 113-118 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  In this work, an expert system was developed and applied for on-line control and supervision of ethanolic fermentation by immobilized Saccharomyces cerevisiae in a fixed-bed pulsed bioreactor of 1.2 l of working volume. A number of experiments with different substrate concentrations (75, 100, 150 and 200 g/l) and hydraulic residence times (2.4, 1.2 and 0.8 h) were carried out. Knowledge-based computer-aided supervision of this process involves accurate on-line measurement of the relevant process variables (temperature, pH, flow rate, carbon dioxide production, etc.). Carbon dioxide production was used for the estimation of the ethanol productivity. The analysis of the measured data allowed to detect states or trends that may be indicative of process or system failures, providing advices and/or alarms. The results showed the reliability of the control system. In previous works, it was proven that pulsing the feed stream highly improves the productivity of fermentation processes carried out in fixed-bed bioreactors [14, 15, 16]. The amplitude and frequency of the pulsation, which is a key factor in the performance of a pulsed feed bioreactor [13], was selected by the control system by using an algorithm allowing the ethanol productivity to be optimized. The pulsation frequency which maximizes the ethanol productivity, presents a high dependency on the hydraulic residence time and the feeding substrate concentration. When increasing the substrate concentration the optimum pulsation frequency also increases; when increasing the hydraulic residence time the optimum pulsation frequency decreases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369427
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  • 9
    Electronic Resource
    Electronic Resource
    Manganese Peroxidase production by Bjerkandera sp. BOS55 (2000)
    Springer
    Bioprocess engineering 23 (2000), S. 663-667 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The use of ligninolytic enzymes in biotechnological applications requires a highly effective production system, with sufficient amounts of the enzymes to be applied in experimental research and herein after at large-scale operations. To reach this final goal, we propose scale-up of ligninolytic production of one of the most well-known enzymes, Manganese Peroxidase (MnP), by Bjerkandera sp. BOS55. Taking into account previous results obtained in shaken flask cultures, MnP production was attempted in stirred fermenters of 2, 10 and 50 l, with levels of activity comparable to those obtained at a lower scale. Additionally, environmental factors as agitation rate, fungus immobilisation and use of buffer were evaluated to maximise MnP production. A fed-batch strategy was proved to reactivate MnP production and to maintain MnP activity for a longer period of time. Operational parameters, such as pH and Redox potential, monitored along the fermentation were found to be useful indicators of MnP production. These variables experimented drastic changes at the MnP peak production, signalling the right moment to collect the enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004490000217
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  • 10
    Electronic Resource
    Electronic Resource
    Manganese peroxidase production by Bjerkandera sp. BOS55 (2000)
    Springer
    Bioprocess engineering 23 (2000), S. 657-661 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The white-rot fungus Bjerkandera sp. BOS55 has been suggested as a good alternative for the production of ligninolytic enzymes, specially Manganese peroxidase (MnP), by its potential ability to degrade complex compounds. However, the application of this fungus requires the complete knowledge of the fermentation pattern in submerged cultures, conditions similar to those existing in industrial size reactors. For this purpose, the nutritional and environmental factors enabling high ligninolytic activity were studied. According to the results, under limitation and sufficiency of nitrogen, there is a threshold concentration for nitrogen from which MnP is produced. However, under nitrogen excess, the ligninolytic stage of the fungus was coincident with growth, with no apparent substrate limitation according to existing levels of carbon and nitrogen. Concerning carbon concentration, MnP synthesis took place independently of glucose concentration, this indicating that carbon limitation does not seem to be the triggering factor for MnP secretion. Other two environmental factors were studied: oxygenation and agitation, but no significant effect on MnP production was observed, a quite different aspect from the behaviour of other known fungi like Phanerochaete chrysosporium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004490000216
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