Breaking the Glucose Feedback Barrier: An Integrated Process Enables Efficient High-Solid L-lactic

During saccharification and fermentation, glucose feedback inhibition severely restricts enzymatic hydrolysis efficiency. To address this issue, an integrated Mild Pretreatment-Pre-Enzymatic Hydrolysis-High-Solid Synchronized State Fermentation (MP-PEH-HSSF) process was developed using corn stover (CS) for efficient lactic acid production. In the mild pretreatment (MP) stage, treatment with low-dosage sodium hydroxide (0.02gg⁻¹ CS) and 5% (w/w) aqueous ammonia at 50% solid loading achieved 43.01% lignin removal while reducing chemical consumption. In the pre-enzymatic hydrolysis (PEH) stage, optimized enzymatic conditions and a staged enzyme addition strategy (PEH:EH = 3:7) effectively alleviated product inhibition, increasing cellulose and hemicellulose conversion rates to 45.72% and 30.01%, respectively. In the high-solid synchronized saccharification and fermentation (HSSF) stage, at a solid loading of 30% (w/w), PEH markedly enhanced the release of fermentable sugars, with a peak glucose concentration of 36.86gL⁻¹. Among six screened L-lactic bacteria, Lacticaseibacillus rhamnosus exhibited the best performance, achieving a L-L-lactic titer of 49.57gL^-1 with an optical purity of 97.12%, and a yield of 0.165gg^-1 of pretreated CS. In addition, the xylose recovery from fermentation residues reached 83.27%, enabling efficient cascade utilization of carbon sources. Overall, the proposed MP-PEH-HSSF integrated strategy effectively mitigates glucose feedback inhibition, enhances the overall conversion efficiency of CS, and improves L-lactic production, providing a feasible pathway for the high-value utilization of lignocellulosic biomass.