Cellulose saccharification to alleviate CCR of xylose for enhanced 1, 2, 4-butanetriol production

1,2,4-Butanetriol (BT) is a valuable polyol with applications in pharmaceuticals, materials, and military sectors. BT biosynthesis primarily uses xylose as substrate, with glucose supporting cell growth. However, glucose-mediated carbon catabolite repression (CCR) suppresses xylose assimilation, limiting BT production. This study aimed to investigate the impact of glucose on xylose-driven BT production in dual-carbon-source utilization and to develop a cellulose-based simultaneous saccharification and fermentation (SSF) strategy for enhanced glucose management, thereby alleviating CCR and improving BT yields. Heterologous BT biosynthesis pathways were introduced into Escherichia coli, with catabolic genes xylAB and yiaE/ycdW knocked out and xylose transporter xylE overexpressed, the BT synthesis pathway was constructed. Optimized fermentation conditions yielded 2.85 g/L BT. Next, the glucose-xylose ratio was optimized by adding xylose at early exponential phase, while low initial glucose with fed-batch feeding significantly reduced CCR, resulting in a BT titer of 3.59 g/L. To further alleviate CCR, an SSF strategy with continuous low-concentration glucose supply from cellulose was implemented, achieving 4.48 g/L BT. Finally, cellulose-xylan co-utilization strategy yielded 1.35 g/L BT. This study provides a reference for alleviating the CCR effect caused by the utilization of dual-carbon-source in biosynthesizing BT, and offers insights for producing BT from lignocellulose.