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

Abstract

The use of all sugars from biomass fractionation – that is, 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 is the conversion of pentoses, especially when mixed with hexoses. Improving sugar conversion in co-fermentation is a major challenge, which was explored in this work. Co-culture using Saccharomyces cerevisiae and evolved Kluyveromyces marxianus strains was evaluated by screening using 24 deep-well plates. Glucose depletion and 83% of xylose conversion were achieved with supplemented hemicellulosic hydrolysate medium (medium volume corresponding to 2/5 of deep-well volume), and initial cell concentrations of 2.5 g L-1 for each yeast, incubated at 150 rpm. 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.