Production of lactic acid from corn straw: One step and two step pre-Treatment strategies and bioconversion efficiency evaluation

As a rich and low-cost lignocellulosic biomass, corn straw (CS) holds great potential for enzymatic saccharification and subsequent bioconversion into high-value-Added chemicals, although its efficiency heavily depends on pretreatment strategies. This study employed two sequential pretreatment strategies-alkaline catalysis and alkaline-ultra-dilute acid treatment-to enhance the processability of CS. Alkaline pretreatment removed 61.18% of lignin, yielding delignified corn straw (CS-RL). Subsequently, CS-RL was subjected to ultra-dilute acid hydrolysis, resulting in the degradation of 75.8% of the hemicellulose and ultimately yielding a hemicellulose-removed substrate (CS-RLHC). Enzymatic hydrolysis of CS-RL and CS-RLHC yielded reducing sugars at rates of 86.58% and 95.54%, respectively. Separate hydrolysis and fermentation (SHF) converted these sugars to lactic acid (LA) at rates of 67.43% and 63.65%. While the two-step pretreatment enhanced enzymatic efficiency, it also generated inhibitors that reduced LA conversion rates. We further explored simultaneous saccharification and fermentation (SSF) and biofilm-based immobilized fermentation (BIF) using CS-RL for LA production, demonstrating their potential for cost-effective industrial applications. These findings provide valuable insights into industrial lactic acid production from lignocellulosic biomass.