Hydrolysis of pretreated lignocellulosic biomass releases pentoses and hexoses. Ethanol production incorporating co-culture of hexose and pentose fermenting microorganisms in lignocellulose hydrolysates is gaining importance. However, 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 wild strain of hexose fermenting Saccharomyces cerevisiae (NRRL Y-132) and pentose fermenting Scheffersomyces stipitis (NCIM 3507) in fermentation media containing glucose and xylose, under microaerophilic conditions. The model equations consider the dissolved oxygen dependence of Scheffersomyces stipitis's growth rate. The model predictions were statistically validated conducting t-test and evaluating indices of agreement. Willmott's index of agreement for the models predicting the concentration profiles of Saccharomyces cerevisiae, Scheffersomyces stipitis, glucose, xylose, ethanol and oxygen 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.