Assessment of multiple pretreatment strategies for 2G L-lactic acid production from sugarcane bagasse

The bioprospecting of sugarcane bagasse (SCB) through alkali, acid, and hydrodynamic cavitation pretreatment methods and their combinations were evaluated based on bagasse composition, enzymatic hydrolysis, and lactic acid productivity using Bacillus coagulans NCIM 5648. From 100.0 g of SCB, L-lactic acid production of 26.16 g, 8.78 g, 14.15 g, 14.33 g, and 24.61 g in alkali, acid, sequential acid-alkali, sequential alkali-acid, and cavitation with alkali pretreatment was obtained, respectively. Considering the holistic approach from SCB to L-lactic acid, alkali pretreatment is found to be the best method with L-lactic acid titer of 68.7 g/L, the productivity of 2.86 g/L/h, and yield of 0.92 g/g which has resulted in 82.5% higher product yield from SCB as compared to alkali-acid pretreatment. Cavitation in presence of alkali evolved as the next better route with L-lactic acid titer of 62.5 g/L, the productivity of 2.60 g/L/h, and yield of 0.92 g/g. Though the highest glucose release of 89.3 g/L was achieved during enzymatic hydrolysis with sequential alkali-acid-pretreated SCB that resulted in the highest L-lactic acid titer of 71.8 g/L, the productivity of 2.99 g/L/h and fermentation yield of 0.90 g/g.