D-Lactic acid production by Sporolactobacillus inulinus YBS1-5 with simultaneous utilization of cottonseed meal and corncob residue

D-Lactic acid, is an important organic acid produced from agro-industrial wastes by Sporolactobacillus inulinus YBS1-5 was investigated to reduce the raw material cost of fermentation. The YBS1-5 strain could produce d-lactic acid by using cottonseed meal as the sole nitrogen source. For efficient utilization, the cottonseed meal was enzymatically hydrolyzed and simultaneously utilized during d-lactic acid fermentation. Corncob residues are rich in cellulose and can be enzymatically hydrolyzed without pretreatment. The hydrolysate of this lignocellulosic waste could be utilized by strain YBS1-5 as a carbon source for d-lactic acid production. Under optimal conditions, a high d-lactic acid concentration (107.2 g/L) was obtained in 7-L fed-batch fermenter, with an average productivity of 1.19 g/L/h and a yield of 0.85 g/g glucose. The optical purity of d-lactic acid in the broth was 99.2%. This study presented a new approach for low-cost production of d-lactic acid for an industrial application.