Advancements in sustainable lactic acid production: revolutionizing biorefineries by harnessing genetically engineered LAB and lignocellulosic biomass

The fermentative production of lactic acid from lignocellulosic biomass as a renewable feedstock addresses the challenges which include high feedstock costs, and biomass recalcitrance. These pretreatment processes, such as organosolv fractionation and high-solids enzymatic saccharification, enhanced sugar recovery by achieving a 566.6 g/bagasse Kg yield. The application of genetic engineering to lactic acid bacteria (LAB) improved efficiencies even further, as shown by the engineered strains Bacillus coagulans which achieved lactic acid yields of 110 g/L under optimized fermentation conditions. The application of advanced technologies like the use of twin-screw extrusion systems and green or eco-friendly solvent systems aided in the process efficiency and carbohydrate recovery. The study demonstrated the latest innovations, such as the application of CRISPR/Cas9 for strain improvement to overcome tolerances against inhibitors and optimize substrate utilization. Moreover, co-fermentation and integrated saccharification approaches upgraded the overall process of sustainable treatment and reduced the production cost. This review highlights the lactic acid (LA) potential in the sugar industry alongside its use in bio-based fuel production. Future research should concentrate on optimizing other genetically engineered techniques to improve LAB performance, exploring cost-effective and energy-efficient pretreatment and saccharification methods, incorporating lactic acid production into industrial processes, and addressing regulatory and market acceptance issues for genetically modified LAB in commercial applications. Sugarcane bagasse (SCB) is recognized as an economically advantageous, renewable lignocellulosic feedstock with a significantly elevated sugar recovery yield of up to 566.6 g/kg. Organsolv fractionation followed by high-solids enzymatic saccharification greatly reduces biomass recalcitrance and increases the availability of fermentable sugars. CRISPR/Cas9-engineered lactic acid bacteria greatly enhance inhibitor tolerance, substrate utilization, and lactic acid yields (up to 110 g/L). High-purity lactic acid recovery is achieved through downstream processing methods such as membrane separation and molecular distillation. Lignocellulosic hydrolysates contain both hexose and pentose sugars which can be fermented by genetically engineered microbial platforms.