Production of optically pure D-lactic acid from brown rice using metabolically engineered Lactobacillus plantarum.
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.
Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Kenji
K
Okano
Bio-energy Corporation, Research & Development Laboratory, 2-9-7 Minaminanamatsu, Amagasaki, 660-0053, Japan.
Shinji
S
Hama
Bio-energy Corporation, Research & Development Laboratory, 2-9-7 Minaminanamatsu, Amagasaki, 660-0053, Japan.
Maki
M
Kihara
Bio-energy Corporation, Research & Development Laboratory, 2-9-7 Minaminanamatsu, Amagasaki, 660-0053, Japan.
Hideo
H
Noda
Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan.
Tsutomu
T
Tanaka
Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan. akondo@kobe-u.ac.jp.
Akihiko
A
Kondo
D019149:Bioreactors / Q000382:microbiology*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000235:genetics*; D019344:Lactic Acid / Q000096:biosynthesis*; D048191:Lactiplantibacillus plantarum / Q000235:genetics* / Q000378:metabolism*; D060847:Metabolic Engineering; D012275:Oryza / Q000378:metabolism*
D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase; D005947:Glucose
Acid adaptation; Brown rice; D-lactic acid; Lactobacillus plantarum; Simultaneous saccharification and fermentation