OPTIMIZED CO-FERMENTATION OF GLUCOSE-XYLOSE MIXTURES BY SACCHAROMYCES CEREVISIAE AND SCHEFFERSOMYCES STIPITIS CO-CULTURE FOR MATHEMATICAL MODELLING

Abstract

Economical production of ethanol from bio-based processes requires the utilization of both hexose and pentose sugars. Although conversion of the sugar mixture (available in different lignocellulosic feedstock) into ethanol is being carried out by various strains of the same or different organisms in co-culture system, very few models are available to predict the fate and the interaction between these microorganisms during fermentation. In this study, mathematical models are proposed to predict the dynamics involved in the co-culture of hexose fermenting Saccharomyces cerevisiae(wild strain) and pentose fermenting Scheffersomyces stipitis(NCIM 3507) in fermentation media containing glucose and xylose, under microaerophilic conditions. The models were statistically validated conducting t-test and evaluating indices of agreement. Wilmott’s index of agreement for the models predicting the concentration profiles of Saccharomyces cerevisiae, Scheffersomyces stipitis, glucose, xylose, ethanol and oxygen concentrations were 0.867, 0.929, 0.980, 0.995, 0.910 and 0.850, respectively, satisfying the criteria for ‘very high’ agreement between model-predicted and experimental values. The co-culture models described in this work can prove to be a valuable tool for quick optimization of S. stipitis and S. cerevisiae co-culture for ethanol production from lignocellulose efficiently and in a sustainable way so that it can be implemented to encounter the economic necessities of the lignocellulosic ethanol industry.