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Todor Vasiljevic - One of the best experts on this subject based on the ideXlab platform.
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lactose hydrolysis in milk as affected by neutralizers used for the preparation of crude β galactosidase extracts from lactobacillus bulgaricus 11842
Innovative Food Science and Emerging Technologies, 2002Co-Authors: Todor Vasiljevic, Piotr JeleńAbstract:Three different neutralizers (NaOH, KOH, NH4OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH4OH as a neutralizer resulted in significantly (P 0.05) difference in kcat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial Enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the Enzyme Deactivation occurred within 1–1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P<0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses.
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lactose hydrolysis in milk as affected by neutralizers used for the preparation of crude β galactosidase extracts from lactobacillus bulgaricus 11842
Innovative Food Science and Emerging Technologies, 2002Co-Authors: Todor Vasiljevic, P JelenAbstract:Three different neutralizers (NaOH, KOH, NH4OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH4OH as a neutralizer resulted in significantly (P 0.05) difference in kcat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial Enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the Enzyme Deactivation occurred within 1–1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P<0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses.
Joseph T.y. Wong - One of the best experts on this subject based on the ideXlab platform.
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type ii topoisomerase activities in both the g1 and g2 m phases of the dinoflagellate cell cycle
Chromosoma, 2005Co-Authors: Carmen K.m. Mak, Victor K. L. Hung, Joseph T.y. WongAbstract:Dinoflagellate genomes are large (up to 200 pg) and are encoded in histoneless chromosomes that are quasi-permanently condensed. This unique combination of chromosomal characteristics presents additional topological and cell cycle control problems for a eukaryotic cell, potentially exhibiting novel regulatory requirements of topoisomerase II. The heterotrophic dinoflagellate Crypthecodinium cohnii was used in this study. The topoisomerase II activities throughout its cell cycle were investigated by DNA flow cytometry following Enzyme Deactivation. Fluorescence microscopy was also used for studying the chromosome morphology of the treated cells. Two classes of topoisomerase II inhibitors were applied in our study, both of which caused G1 delay as well as G2/M arrest in the C. cohnii cell cycle. At high doses, the topoisomerase poisons amsacrine and ellipticine induced DNA fragmentation in C. cohnii cells. Topoisomerase II activities, as measured by the ability to decatenate kinetoplastid DNA (kDNA), are normally detected throughout the cell cycle in C. cohnii. Our results suggest that the requirement of type II topoisomerase activities during the G1 phase of the cell cycle may relate to the unwinding of quasi-permanently condensed chromosomes for the purpose of transcription. This was also the first time that topoisomerase II activity in dinoflagellate cells was detected.
P Jelen - One of the best experts on this subject based on the ideXlab platform.
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lactose hydrolysis in milk as affected by neutralizers used for the preparation of crude β galactosidase extracts from lactobacillus bulgaricus 11842
Innovative Food Science and Emerging Technologies, 2002Co-Authors: Todor Vasiljevic, P JelenAbstract:Three different neutralizers (NaOH, KOH, NH4OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH4OH as a neutralizer resulted in significantly (P 0.05) difference in kcat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial Enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the Enzyme Deactivation occurred within 1–1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P<0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses.
Piotr Jeleń - One of the best experts on this subject based on the ideXlab platform.
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lactose hydrolysis in milk as affected by neutralizers used for the preparation of crude β galactosidase extracts from lactobacillus bulgaricus 11842
Innovative Food Science and Emerging Technologies, 2002Co-Authors: Todor Vasiljevic, Piotr JeleńAbstract:Three different neutralizers (NaOH, KOH, NH4OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH4OH as a neutralizer resulted in significantly (P 0.05) difference in kcat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial Enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the Enzyme Deactivation occurred within 1–1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P<0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses.
đurđa Vasicracki - One of the best experts on this subject based on the ideXlab platform.
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modelling of continuous l malic acid production by porcine heart fumarase and fumarase in yeast cells
Chemical and Biochemical Engineering Quarterly, 2009Co-Authors: Vrsalovic A Presecki, Bruno Zelic, đurđa VasicrackiAbstract:Continuous production of L-malic acid will be presented in this paper.The fumarase isolated from porcine heart, fumarase in the permeabilized non-growing cells of baker’s yeast and Saccharomyces bayanus (UVAFERM BC) were used as biocatalysts.In the pro duction of L-malic acid with fumarase isolated from porcine hearts, there was no Enzyme Deactivation for a period of two days.At the average residence time of 4 hours, the conversion of about 80 % was achieved.Inactivation of the Enzyme was observed using permeabilized cells.This inactivation is described as a reversible process.Conversion of about 50 % was achieved with the remaining Enzyme activity.A mathematical model that describes the pro duction of L-malic acid, which contains the Enzyme inactivation rate, was developed.Based on simulations, the used biocatalysts were compared.The results show that in the continuous production of L-malic acid, one milligram of purified Enzyme corresponds to 68 g (wet weight) cells of Saccharomyces bayanus or 120 g (wet weight) cells of baker’s yeast.
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coEnzyme regeneration catalyzed by nadh oxidase from lactobacillus brevis in the reaction of l amino acid oxidation
Biochemical Engineering Journal, 2008Co-Authors: Zvjezdana Findrik, Ines Simunovic, đurđa VasicrackiAbstract:Abstract In this paper l -methionine oxidation catalyzed by l -phenylalanine dehydrogenase from Rhodococcus sp. M4 was studied. It was found that the reaction equilibrium is shifted to the side of reduction, and it was therefore necessary to regenerate NAD+ to increase l -methionine conversion. NADH oxidase from Lactobacillus brevis was used for that purpose. The Enzyme was kinetically characterized. It was found that the Enzyme is inhibited by NAD+. Hence, NADH oxidation catalyzed by NADH oxidase was described by the Michaelis–Menten equation which included anticompetitive NAD+ inhibition. l -Methionine oxidation was described by formal double-substrate Michaelis–Menten model which included competitive product inhibition by NADH. 2-Oxo-4-methylthiobutyric acid reduction was described by formal three-substrate Michaelis–Menten kinetics which included competitive inhibition by NAD+. Experiments were carried out in the batch and in the continuously operated Enzyme membrane reactor. 100% l -methionine conversion was achieved in the batch reactor. The conversion was lower in the continuously operated Enzyme membrane reactor where Enzyme Deactivation occurred.