Kinetics Of Lactic Acid Production In Alcohol Fermentation By Several Strains Of Saccharomyce

The lactic acid is a important kind of flavor substance，there’s no article about thekinetics of saccharomyces cerevisiae producing lactic acid in China. The object initiallyidentified that the style of saccharomyces cerevisiae producing lactic acid couples productformation and cell growth. The methods of assaying the yeast’s concentration, the lactic acid’sconcentration, the pyruvic acid’s concentration and the residual glucose’s concentration in thefermentation process were determined. We assayed the biomass produced in the fermentationprocess by the dry weight method, the lactic acid’s content by the visible spectrophotometrymethod, the hydroxy biphenyl as the colour-display reagent, the residual glucose’sconcentration by the3,5-dinitrosalicylic acid method and the pyruvic acid’s concentration bythe2,4-dinitrophenylhydrazine colorimetric method as chromogenic agent. Eight standardcurves were made. They are the residual glucose’s standard curve, the dry weight’s standardcurve of the No.1wine yeast etc., the lactic acid’s standard curve, the pyruvic acid’s standardcurve The formulas of assaying the residual glucose’s concentration, the pyruvic acid’sconcentration, the5kinds of the saccharomyces cerevisiae’s dry weight, and the lactic acidare defined by regression equation.The culture temperature of yeast is30℃. The medium is made up with corn syrup at2g/L and glucose at different concentration. The models of the yeast growth kinetics, the lacticacid kinetics produced by yeast fermentation, and the substrate consumption kinetics wareestablished by Origin8.0software through the Logistic equation and the Luedeking-Piretequation, then the fitting of their equations ware completed. We estimated the kineticsequation parameters of the yeast cell growth, the lactic acid production, and the substrateconsumption.The results show that the kinetics model of the lactic acid production belongs to Ⅰstyle,coupling product formation and cell growth. The final ratio of the lactic acid produced bythese saccharomyces cerevisiae accounting for the substrate glucose is between0.4%and0.8%, the final ratio of the lactic acid produced by brewer’s yeast eventually accounting for the substrate glucose is lower. The final ratio of the lactic acid produced by the alcohol yeasteventually accounting for the substrate glucose is higher. The final lactic acid wine yeast andother yeast increased with the increase of the concentration of glucose, the final ratio of thelactic acid produced by the NO.1wine yeast accounting for the substrate glucose increasedwith the increase of glucose concentration. The final ratio of the lactic acid produced bybrewer’s yeast and alcohol yeast accounting for the substrate glucose decreased with theincrease of glucose concentration. The final lactic acid amount of the beer yeast is lower, thealcohol yeast’s is higher, and the rest yeast’s is moderate.