14 research outputs found
Aumento na produção de biomassa de levedura em propagador aerado por processo descontĂnuo e semicontĂnuo para produção de cachaça
Incorporation of copper ions by yeast Kluyveromyces marxianus during cultivation on whey
The production of
Kluyveromyces marxianus
biomass enriched with copper ions were studied. For that reason the growth of
Kluyveromyces marxianus
in whey with different concentrations of copper ions in batch process under semiaerobic and aerobic conditions were examined. The kinetics of copper ions accumulation in yeast cells, under the same conditions, as well as the reduction of chemical oxygen demand (COD) during yeast growth in aerobic condition, were monitored, as well. The concentration of copper ions in media up to 4 mg lâ1 did not affect the yeast growth, whereas at a higher concentration, a marked decrease in the rate of yeast growth, ethanol production and lactose consumption occurred. In semiaerobic conditions, the maximum uptake of 0.35 mg Cu gâ1 d.m. was obtained, while in aerobic conditions a lower uptake of 0.26 mg Cu gâ1 d.m. and COD reduction of 85% were achieved. COD reduction was independent of the copper addition or uptake
Uptake of iron by yeast cells and its impact on biomass production
Procedures for the production of Saccharomyces cerevisiae biomass enriched with iron and the effects of the iron ions addition into the molasses medium on the yeast growth and the production of ethanol were studied. The growth of the yeast S. cerevisiae and the ethanol production in media with different concentrations of Fe were monitored in the batch process under semiaerobic and anaerobic conditions. The highest biomass concentration and ethanol production were achieved in the medium with 0.6-0.8 g l-1 of Fe under both (semiaerobic and anaerobic) conditions. Kinetics of the iron ions accumulation in yeast cells during 24 h of growth in the batch process under semiaerobic and anaerobic conditions were monitored. In anaerobic conditions the maximum uptake (10 mg g-1 d.m. yeast biomass) was obtained after 12 h of fermentation, while in semiaerobic conditions a four times lower uptake (2.5 mg g-1 d.m. yeast biomass) was obtained after 16 h of fermentation
Enhancement of Trigonopsis variabilis D-Amino Acid Oxidase Overproduction in Fed-batch Cultivation of Escherichia coli
D-Amino acid oxidase is a key enzyme in the production of semisynthetic cephalosporins. The Trigonopsis variabilis D-amino acid oxidase with 12- amino-acid peptide at N-terminus was expressed in Escherichia coli BL21(DE3), in a series of short fed-batch cultivations. The strategy of gradual induction and gradual feeding with D-methionine during expression resulted in active enzyme production twice as high as that in which the inducer and methionine were added all at once at the expression start. In optimal conditions during 14 h of aerobic cultivation, 350 mg Lâ1 of active enzyme was produced