Comparative fermentability of a glucose/xylose enriched enzymatic slurry using different yeast strains

Lignocellulosic biomass represents a sustainable energy source as ethanol fuel demand increases; process integration and efficient C6/C5 sugars utilization are essential for achieving techno-economically viable production. Here, alkaline-sulfite pretreatment combined with disc refining was applied to sugarcane bagasse for conserving most of cellulose and hemicellulose fractions. Then, β-glucosidase supplementation of cellulase at rational enzyme dosage (18 FPU/g biomass) was established for the enzymatic hydrolysis of the pretreated solids, achieving approximately 75% conversion yield for both cellulose and xylan. The resulting enzymatic slurry was directly fermented without solid-liquid separation and used to evaluate the effects of temperature and nutrient supplementation on ethanol fermentation by three yeast strains. Under optimal conditions (30 °C with nutrients), Kluyveromyces marxianus Y-6860 exhibited higher ethanol productivity ( $${Q_P}$$ = 3.25 g L− 1 h− 1) than Saccharomyces cerevisiae PE-2 ( $${Q_P}$$ = 2.17 g L− 1 h− 1). Notably, Scheffersomyces stipitis Y-7124 was the only strain capable of significantly consuming xylose, resulting in 46% higher ethanol production than the other strains. To simulate industrially relevant conditions, the slurry was supplemented with anhydrous glucose up to 100.0 g L− 1. Under these conditions, K. marxianus Y-6860 and S. cerevisiae PE-2 maintained robust fermentation performance, while S. stipitis Y-7124 exhibited limited xylose uptake during the evaluated period. The results demonstrate the potential of direct slurry fermentation for integrated 2G ethanol production, with K. marxianus Y-6860 showing strong potential for industrial-scale glucose fermentation and S. stipitis Y-7124 being a prospective candidate for improving xylose conversion. Graphical abstract