Production of optically pure d-lactic acid from brown rice using metabolically engineered Lactobacillus plantarum

• Published in: Applied microbiology and biotechnology 2017-03, Vol.101 (5), p.1869-1875
• Main Authors: Okano, Kenji, Hama, Shinji, Kihara, Maki, Noda, Hideo, Tanaka, Tsutomu, Kondo, Akihiko
• Format: Article
• Language: English
• Subjects: Acids; Bacteria; Biomass; Biomedical and Life Sciences; Bioreactors - microbiology; Biotechnological Products and Process Engineering; Biotechnology; Dehydrogenases; Engineering; Engineering schools; Enzymes; Fermentation; Glucose; Glucose - metabolism; L-Lactate Dehydrogenase - genetics; Lactic Acid - biosynthesis; Lactobacillus plantarum; Lactobacillus plantarum - genetics; Lactobacillus plantarum - metabolism; Life Sciences; Metabolic Engineering; Microbial Genetics and Genomics; Microbiology; Nutrients; Oryza - metabolism; Rice; Studies
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-016-7976-8

Simultaneous saccharification and fermentation (SSF) of d -lactic acid was performed using brown rice as both a substrate and a nutrient source. An engineered Lactobacillus plantarum NCIMB 8826 strain, in which the ʟ-lactate dehydrogenase gene was disrupted, produced 97.7 g/L d -lactic acid from 20% ( w / v ) brown rice without any nutrient supplementation. However, a significant amount of glucose remained unconsumed and the yield of lactic acid was as low as 0.75 (g/g-glucose contained in brown rice). Interestingly, the glucose consumption was significantly improved by adapting L. plantarum cells to the low-pH condition during the early stage of SSF (8–17 h). As a result, 117.1 g/L d -lactic acid was produced with a high yield of 0.93 and an optical purity of 99.6% after 144 h of fermentation. SSF experiments were repeatedly performed for ten times and d -lactic acid was stably produced using recycled cells (118.4–129.8 g/L). On average, d -lactic acid was produced with a volumetric productivity of 2.18 g/L/h over 48 h.