Co-production of L-lactic acid and xylitol from corn stover by high-solid loading alkali-ammonia pretreatment

Developing environmentally friendly and low-toxicity pretreatment methods is essential for advancing sustainable biorefinery processes. This study introduced an alkali-ammonia pretreatment at high-solid loading combined with co-production of L-lactic (L-LA) and xylitol, achieving high-value utilization of corn stover (CS). Through a fed-batch strategy, the process achieved a cellulose conversion rate of 84.51 % and a hemicellulose conversion rate of 67.12 % at 30 % solid loading, while eliminating the need for energy-intensive drying and detoxification steps. The obtained hydrolysate was subsequently employed for efficient two-stage fermentation: (1) L-LA fermentation yielded 78.21 g/L with 97.87 % optical purity upon 2 % nitrogen supplementation, and (2) xylitol fermentation achieved 16.48 g/L with a 0.51 g/g xylose yield. Overall, this easily operated and low-toxicity pretreatment effectively disrupted the recalcitrant structure of CS, enhanced product formation, and demonstrated strong potential as a promising and sustainable biorefinery strategy.