Fed-batch simultaneous saccharification and fermentation for valorization of sugarcane bagasse to lactic acid and evaluation of the residual solids as nutrient-rich feed ingredient

• Biorefinery process development for valorization of sugarcane bagasse. • Multiple feedings influenced lactic acid yield and fermentation efficiency. • Residual solids obtained after the fermentation have a potential as a feed ingredient. • Sustainable approach for producing valuable bioproducts from agro-industrial waste. Sugarcane bagasse (SB) is one of the high-potential fermentation feedstocks due to its ready availability, low cost, and high cellulose content. In this study, SB was delignified using a deep eutectic solvent (DES) prepared from lactic acid (LA) and choline chloride (ChCl), and used as the sole substrate for LA production by Lactiplantibacillus plantarum TS-KKU P-8. Three fermentation process configurations were tested, i.e., batch, fed-batch simultaneous saccharification and fermentation (SSF) with a single feeding of pre-hydrolyzed SB, and SSF with double feeding of pre-hydrolyzed SB. The batch process produced 20.2 ± 0.5 g-LA, with a yield and fermentation efficiency of 0.48 ± 0.0 g-LA/g-SB and 71.3 ± 0.0 %, respectively. In the fed-batch process with a single feeding, LA production increased to 38.7 ± 1.9 g-LA, with a yield and fermentation efficiency of 0.49 ± 0.0 g-LA/g-SB and 71.0 ± 0.0 %, respectively. This process enhanced LA productivity by 89 % compared to the batch process (0.36 against 0.19 g/h). However, when pre-hydrolyzed SB was fed twice into the bioreactor, a drop in LA yield and fermentation efficiency was observed. Additionally, the residual solids remaining after the fermentation were evaluated for animal feed application. Their nutrient profile was comparable to other common feed ingredients, implying their applicability as a low-cost feed ingredient substitute.