The growth and activity of formate dehydrogenase (FDH) in five methanol-utilizing yeasts at vario... more The growth and activity of formate dehydrogenase (FDH) in five methanol-utilizing yeasts at various methanol concentrations were investigated. The parameters observed were inhibited at 4% methanol concentration in the medium. For Candida boidinii and Pichia trehalophila FDH activity was not found. The highest value was detected for Pichia lindneri (0.14 U/mg protein).
Bioprocess and Biosystems Engineering, Aug 6, 2004
In this contribution, the advantages of the artificial neural network approach to the identificat... more In this contribution, the advantages of the artificial neural network approach to the identification and control of a laboratory-scale biochemical reactor are demonstrated. It is very important to be able to maintain the levels of two process variables, pH and dissolved oxygen (DO) concentration, over the course of fermentation in biosystems control. A PC-supported, fully automated, multi-task control system has been designed and built by the authors. Forward and inverse neural process models are used to identify and control both the pH and the DO concentration in a fermenter containing a Saccharomyces cerevisiae based-culture. The models are trained off-line, using a modified back-propagation algorithm based on conjugate gradients. The inverse neural controller is augmented by a new adaptive term that results in a system with robust performance. Experimental results have confirmed that the regulatory and tracking performances of the control system proposed are good.
The possibility to discriminate the three-step mechanisms of thermal inactivation of jack bean ur... more The possibility to discriminate the three-step mechanisms of thermal inactivation of jack bean urease was analyzed, the models being suggested in a previous study from the activity data. The simulations of the concentration courses of individual structural forms of urease incorporated in the mechanisms were performed. The results showed that all mechanisms could be discriminated if the dynamics of the evolution of oligomeric structural forms of urease was monitored. A careful choice of temperatures and combination of several analytical techniques is, however, required to achieve a reliable discrimination of the inactivation mechanism.
The growth and activity of formate dehydrogenase (FDH) in five methanol-utilizing yeasts at vario... more The growth and activity of formate dehydrogenase (FDH) in five methanol-utilizing yeasts at various methanol concentrations were investigated. The parameters observed were inhibited at 4% methanol concentration in the medium. For Candida boidinii and Pichia trehalophila FDH activity was not found. The highest value was detected for Pichia lindneri (0.14 U/mg protein).
The e ect of the initial sucrose concentration (50 g dm−3, 200 g dm−3, and 350 g dm−3) and time o... more The e ect of the initial sucrose concentration (50 g dm−3, 200 g dm−3, and 350 g dm−3) and time of cultivation (1 d, 2 d, and 4 d) on the fructosyltransferase production by Aureobasidium pullulans CCY 27-1-1194 in shaken flask cultivations was investigated. It was found that the overall fructosyltransferase production depended strongly on the initial sucrose concentration when the highest value of enzyme activity (130 000 U dm−3) was achieved at 350 g dm−3 in the fourth cultivation day. The maximum of speci c activity per dry cell mass was achieved at the same sucrose concentration, but already in the second day. Since the second cultivation day, the ratio of the enzyme activity contained in cells and released into medium was 1.3—1.6, independently of sucrose concentration. In order to discuss the fructosyltransferase production in relation to cell growth and state of the culture, the sucrose conversion, produced amount of fructooligosaccharides and organic acids, and the yield fact...
β-Apiosidase is a rare glycosidase applied in winemaking for flavour enhancement. This enzyme is ... more β-Apiosidase is a rare glycosidase applied in winemaking for flavour enhancement. This enzyme is involved in the release of volatile terpenes by hydrolysis of their odourless glycosidic precursors. It is found as a minor component in commercial pectinase/cellulase preparations. Microbial production of β-apiosidase by two Aspergillus sp. strains was investigated. Apiin-induced production of this extracellular glycosidase was confirmed only during the cultivation of Aspergillus niger CBS 554.65 but the high productivity value reported in the work of Dupin et al. (1992) J. Agric. Food Chem. 40(10): 1886—1891 could not be reproduced. The achieved productivity was by far not satisfactory considering the apiin cost. Commercial enzyme preparations with β-apiosidase side-activity thus remain a better alternative as the enzyme source for biocatalytic applications.
Thermal inactivation of a commercial β-galactosidase from Aspergillus oryzae in a 300 g/L lactose... more Thermal inactivation of a commercial β-galactosidase from Aspergillus oryzae in a 300 g/L lactose solution was studied in the temperature range of 65–75 °C. Lactose exhibited a stabilisation effect when similar inactivation rates as those in lactose solution were observed in a lactose-free solution at temperatures lower by 5°C. Inactivation process in the lactose solution was biphasic. A kinetic model based on the Lumry-Eyring mechanism was proposed and successfully verified. Estimated activation energy values were very different. Rather high activation energy values of the forward reactions were responsible for both the significant change of rate constants and the rate-controlling reaction with temperature. For these two reasons, an increase of the operational lifetime of the enzyme from 7 days at 60 °C to 580 days at 55 °C was predicted.
Thermal inactivation of immobilized glucose isomerase in a concentrated glucose solution was inve... more Thermal inactivation of immobilized glucose isomerase in a concentrated glucose solution was investigated in the batch mode and temperature range of 83–95 °C, which is substantially higher than the temperature used in the industrial production of high-fructose corn syrup. Simultaneous evaluation of all inactivation data showed that first-order kinetics with the Arrhenius temperature dependence of the rate constant provided a good approximation of the biocatalyst stability under the investigated conditions. The model parameters were then used to predict the operational temperature for this biocatalyst in the production of high-fructose corn syrup based on the set operational life-time of the biocatalyst. The simulation predicted a window of operational temperature of 60–65 °C, which corresponds very well with the industrial applications of this biocatalyst. This observation demonstrates that the multi-temperature method of enzyme inactivation can provide a good estimate of biocatalys...
Biotransformation of acetophenone to R-1-phenylethanol with Pichia capsulata immobilized in Caalg... more Biotransformation of acetophenone to R-1-phenylethanol with Pichia capsulata immobilized in Caalginate gel beads was studied. Experiments were carried out in a batch reactor stirred on an orbital shaker (300 rpm) at 25 ℃. Based on experimental data, uncoupled parameters of reaction kinetics (measurements with free cells) and diffusion coefficients (sorption method) were estimated. The model expressing the conversion of acetophenone with immobilized cells in the batch reactor consisted of mass balance equations of acetophenone and R-1-phenylethanol in the liquid and solid phases. A satisfactory agreement between the experimental and predicted values of acetophenone and R-1-phenylethanol concentrations was achieved
2(E)-hexenal is a green note flavour molecule that is widely used in various compositions of arom... more 2(E)-hexenal is a green note flavour molecule that is widely used in various compositions of aromas, flavours and perfumery. As there is considerable demand for naturally produced aromas this article deals with some aspects of this C6-volatile production with regard to the selection of plant source material and reaction conditions. The following plants were tested for this purpose: runner bean (Phaseolus coccineus), common bean (Phaseolus vulgaris), three (Capsicum annuum) bell pepper varieties, garden cress (Lepidium sativum), green slicing cucumber (Cucumis sativa), mung beans (Vigna mungo) and brown lentils (Lens culinaris). Selection of source material was considered on the basis of 2(E)-hexenal yield and productivity. The common bean leafs were able to produce up to 35 mg of 2(E)-hexenal/kg fresh leaves.
Optimal conditions of spray drying of a fructooligosaccharide-rich mixture prepared by enzymatic ... more Optimal conditions of spray drying of a fructooligosaccharide-rich mixture prepared by enzymatic conversion of sucrose were investigated. It was found that efficient drying of the mixture containing about 40 % of monosaccharides and sucrose required addition of a compound with a high glass transition temperature. The addition of maltodextrin helped to achieve satisfactory solids yield and moisture. Optimized process parameters were the feed flow rate and solids concentration, drying air flow rate and inlet temperature.
Efficient chromatographic separation of fructosyltransferase from Aureobasidium pullulans was ach... more Efficient chromatographic separation of fructosyltransferase from Aureobasidium pullulans was achieved on a preparative scale using a weak anion-exchanger Sepabeads FP-DA. The recovery yield was about 70% and the purification factor reached a value of 28. The molecular weight of the enzyme determined by size-exclusion chromatography was 570,000. The enzyme exhibited both hydrolytic and transferase activity when the latter was higher in the whole concentration range and completely dominating at higher sucrose concentrations. It was found that sucrose was the only donor of fructosyl moiety used in the transfer reaction. The initial rate method was used for the investigation of the kinetics of the action of fructosyltransferase on sucrose in the concentration range 30-2,430 mM. The initial transfructosylation rate was well fitted with a linear function of the sucrose activity where the activity coefficient was an exponentially decreasing function of the sucrose concentration.
... For example, the absence of alkaline phosphatase (ALP, EC 3.1.3.1) activity in milk is common... more ... For example, the absence of alkaline phosphatase (ALP, EC 3.1.3.1) activity in milk is commonly used as a standard test for the determination of proper pasteurization of milk (Painter & Bradley, 1997); during pasteurization, the ALP activity should decrease about 500-fold. ...
The growth and activity of formate dehydrogenase (FDH) in five methanol-utilizing yeasts at vario... more The growth and activity of formate dehydrogenase (FDH) in five methanol-utilizing yeasts at various methanol concentrations were investigated. The parameters observed were inhibited at 4% methanol concentration in the medium. For Candida boidinii and Pichia trehalophila FDH activity was not found. The highest value was detected for Pichia lindneri (0.14 U/mg protein).
Bioprocess and Biosystems Engineering, Aug 6, 2004
In this contribution, the advantages of the artificial neural network approach to the identificat... more In this contribution, the advantages of the artificial neural network approach to the identification and control of a laboratory-scale biochemical reactor are demonstrated. It is very important to be able to maintain the levels of two process variables, pH and dissolved oxygen (DO) concentration, over the course of fermentation in biosystems control. A PC-supported, fully automated, multi-task control system has been designed and built by the authors. Forward and inverse neural process models are used to identify and control both the pH and the DO concentration in a fermenter containing a Saccharomyces cerevisiae based-culture. The models are trained off-line, using a modified back-propagation algorithm based on conjugate gradients. The inverse neural controller is augmented by a new adaptive term that results in a system with robust performance. Experimental results have confirmed that the regulatory and tracking performances of the control system proposed are good.
The possibility to discriminate the three-step mechanisms of thermal inactivation of jack bean ur... more The possibility to discriminate the three-step mechanisms of thermal inactivation of jack bean urease was analyzed, the models being suggested in a previous study from the activity data. The simulations of the concentration courses of individual structural forms of urease incorporated in the mechanisms were performed. The results showed that all mechanisms could be discriminated if the dynamics of the evolution of oligomeric structural forms of urease was monitored. A careful choice of temperatures and combination of several analytical techniques is, however, required to achieve a reliable discrimination of the inactivation mechanism.
The growth and activity of formate dehydrogenase (FDH) in five methanol-utilizing yeasts at vario... more The growth and activity of formate dehydrogenase (FDH) in five methanol-utilizing yeasts at various methanol concentrations were investigated. The parameters observed were inhibited at 4% methanol concentration in the medium. For Candida boidinii and Pichia trehalophila FDH activity was not found. The highest value was detected for Pichia lindneri (0.14 U/mg protein).
The e ect of the initial sucrose concentration (50 g dm−3, 200 g dm−3, and 350 g dm−3) and time o... more The e ect of the initial sucrose concentration (50 g dm−3, 200 g dm−3, and 350 g dm−3) and time of cultivation (1 d, 2 d, and 4 d) on the fructosyltransferase production by Aureobasidium pullulans CCY 27-1-1194 in shaken flask cultivations was investigated. It was found that the overall fructosyltransferase production depended strongly on the initial sucrose concentration when the highest value of enzyme activity (130 000 U dm−3) was achieved at 350 g dm−3 in the fourth cultivation day. The maximum of speci c activity per dry cell mass was achieved at the same sucrose concentration, but already in the second day. Since the second cultivation day, the ratio of the enzyme activity contained in cells and released into medium was 1.3—1.6, independently of sucrose concentration. In order to discuss the fructosyltransferase production in relation to cell growth and state of the culture, the sucrose conversion, produced amount of fructooligosaccharides and organic acids, and the yield fact...
β-Apiosidase is a rare glycosidase applied in winemaking for flavour enhancement. This enzyme is ... more β-Apiosidase is a rare glycosidase applied in winemaking for flavour enhancement. This enzyme is involved in the release of volatile terpenes by hydrolysis of their odourless glycosidic precursors. It is found as a minor component in commercial pectinase/cellulase preparations. Microbial production of β-apiosidase by two Aspergillus sp. strains was investigated. Apiin-induced production of this extracellular glycosidase was confirmed only during the cultivation of Aspergillus niger CBS 554.65 but the high productivity value reported in the work of Dupin et al. (1992) J. Agric. Food Chem. 40(10): 1886—1891 could not be reproduced. The achieved productivity was by far not satisfactory considering the apiin cost. Commercial enzyme preparations with β-apiosidase side-activity thus remain a better alternative as the enzyme source for biocatalytic applications.
Thermal inactivation of a commercial β-galactosidase from Aspergillus oryzae in a 300 g/L lactose... more Thermal inactivation of a commercial β-galactosidase from Aspergillus oryzae in a 300 g/L lactose solution was studied in the temperature range of 65–75 °C. Lactose exhibited a stabilisation effect when similar inactivation rates as those in lactose solution were observed in a lactose-free solution at temperatures lower by 5°C. Inactivation process in the lactose solution was biphasic. A kinetic model based on the Lumry-Eyring mechanism was proposed and successfully verified. Estimated activation energy values were very different. Rather high activation energy values of the forward reactions were responsible for both the significant change of rate constants and the rate-controlling reaction with temperature. For these two reasons, an increase of the operational lifetime of the enzyme from 7 days at 60 °C to 580 days at 55 °C was predicted.
Thermal inactivation of immobilized glucose isomerase in a concentrated glucose solution was inve... more Thermal inactivation of immobilized glucose isomerase in a concentrated glucose solution was investigated in the batch mode and temperature range of 83–95 °C, which is substantially higher than the temperature used in the industrial production of high-fructose corn syrup. Simultaneous evaluation of all inactivation data showed that first-order kinetics with the Arrhenius temperature dependence of the rate constant provided a good approximation of the biocatalyst stability under the investigated conditions. The model parameters were then used to predict the operational temperature for this biocatalyst in the production of high-fructose corn syrup based on the set operational life-time of the biocatalyst. The simulation predicted a window of operational temperature of 60–65 °C, which corresponds very well with the industrial applications of this biocatalyst. This observation demonstrates that the multi-temperature method of enzyme inactivation can provide a good estimate of biocatalys...
Biotransformation of acetophenone to R-1-phenylethanol with Pichia capsulata immobilized in Caalg... more Biotransformation of acetophenone to R-1-phenylethanol with Pichia capsulata immobilized in Caalginate gel beads was studied. Experiments were carried out in a batch reactor stirred on an orbital shaker (300 rpm) at 25 ℃. Based on experimental data, uncoupled parameters of reaction kinetics (measurements with free cells) and diffusion coefficients (sorption method) were estimated. The model expressing the conversion of acetophenone with immobilized cells in the batch reactor consisted of mass balance equations of acetophenone and R-1-phenylethanol in the liquid and solid phases. A satisfactory agreement between the experimental and predicted values of acetophenone and R-1-phenylethanol concentrations was achieved
2(E)-hexenal is a green note flavour molecule that is widely used in various compositions of arom... more 2(E)-hexenal is a green note flavour molecule that is widely used in various compositions of aromas, flavours and perfumery. As there is considerable demand for naturally produced aromas this article deals with some aspects of this C6-volatile production with regard to the selection of plant source material and reaction conditions. The following plants were tested for this purpose: runner bean (Phaseolus coccineus), common bean (Phaseolus vulgaris), three (Capsicum annuum) bell pepper varieties, garden cress (Lepidium sativum), green slicing cucumber (Cucumis sativa), mung beans (Vigna mungo) and brown lentils (Lens culinaris). Selection of source material was considered on the basis of 2(E)-hexenal yield and productivity. The common bean leafs were able to produce up to 35 mg of 2(E)-hexenal/kg fresh leaves.
Optimal conditions of spray drying of a fructooligosaccharide-rich mixture prepared by enzymatic ... more Optimal conditions of spray drying of a fructooligosaccharide-rich mixture prepared by enzymatic conversion of sucrose were investigated. It was found that efficient drying of the mixture containing about 40 % of monosaccharides and sucrose required addition of a compound with a high glass transition temperature. The addition of maltodextrin helped to achieve satisfactory solids yield and moisture. Optimized process parameters were the feed flow rate and solids concentration, drying air flow rate and inlet temperature.
Efficient chromatographic separation of fructosyltransferase from Aureobasidium pullulans was ach... more Efficient chromatographic separation of fructosyltransferase from Aureobasidium pullulans was achieved on a preparative scale using a weak anion-exchanger Sepabeads FP-DA. The recovery yield was about 70% and the purification factor reached a value of 28. The molecular weight of the enzyme determined by size-exclusion chromatography was 570,000. The enzyme exhibited both hydrolytic and transferase activity when the latter was higher in the whole concentration range and completely dominating at higher sucrose concentrations. It was found that sucrose was the only donor of fructosyl moiety used in the transfer reaction. The initial rate method was used for the investigation of the kinetics of the action of fructosyltransferase on sucrose in the concentration range 30-2,430 mM. The initial transfructosylation rate was well fitted with a linear function of the sucrose activity where the activity coefficient was an exponentially decreasing function of the sucrose concentration.
... For example, the absence of alkaline phosphatase (ALP, EC 3.1.3.1) activity in milk is common... more ... For example, the absence of alkaline phosphatase (ALP, EC 3.1.3.1) activity in milk is commonly used as a standard test for the determination of proper pasteurization of milk (Painter & Bradley, 1997); during pasteurization, the ALP activity should decrease about 500-fold. ...
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