Elevating fermentation yield of cellulosic lactic acid in calcium lactate form from corn stover feedstock

Abstract

Chiral lactic acid is recovered as sodium lactate or calcium lactate from fermentation broth, then the lactate are released to its lactic acid form as monomer chemical of polylactic acid (PLA). This study investigated the fermentation behaviors of chiral lactic acid from corn stover feedstock when lactic acid was recovered in different lactate forms, calcium lactate or sodium lactate. When chiral lactic acid is recovered in calcium lactate form in the simultaneous saccharification and co-fermentation (SSCF) of corn stover feedstock, L-lactic acid titer reached 130.3 g/L, approximately 14% greater than that in sodium L-lactate form; D-lactic acid titer reached 124.8 g/L, approximately 11.2% greater than that in sodium D-lactate form. The lessened lactate inhibition in calcium lactate form on cellulase activity and cell viability was found to be responsible for the elevated cellulosic L- and D-lactic acid yield. The techno-economic analysis showed the greater economic advantage of chiral lactic acid in calcium lactate than that in sodium lactate. This study provides the strong evidence and simple option for improving cellulosic chiral lactic acid yield.