Screening of yeast co‐culture using crude hydrolysate for co‐fermentation of pentose and hexose

The use of all sugars from biomass fractionation, i.e., hexoses and pentoses, is essential to develop feasible processes in a biorefinery context. Hexoses are converted into different products by most microorganisms, the main issue being the conversion of pentoses, especially when mixed with hexoses. Improving sugar conversion in co-fermentation is a major challenge that was explored in this work. Co-culture using S. cerevisiae and evolved K. marxianus strains was evaluated by a screening using 24 deep-well plates. Glucose depletion and 83% of xylose conversion were achieved from supplemented hemicellulosic hydrolysate, using 2/5 of deep-well volume filled with medium (at 150 rpm) and initial cell concentrations of 2.5 g/L for each yeast. The screening strategy provided reliable data that confirmed the co-culture as a promising approach for the co-assimilation of biomass-derived sugars. The importance of aeration control for effective xylose assimilation was also pointed out.