title: L-Lactic acid production from glycerol coupled with acetic acid metabolism by Enterococcus faecalis without carbon loss.
abstract: Glycerol is a by-product in the biodiesel production process and considered as one of the prospective carbon sources for microbial fermentation including lactic acid fermentation, which has received considerable interest due to its potential application. Enterococcus faecalis isolated in our laboratory produced optically pure L-lactic acid from glycerol in the presence of acetic acid. Gas chromatography-mass spectrometry analysis using [1, 2-(13)C2] acetic acid proved that the E. faecalis strain QU 11 was capable of converting acetic acid to ethanol during lactic acid fermentation of glycerol. This indicated that strain QU 11 restored the redox balance by oxidizing excess NADH though acetic acid metabolism, during ethanol production, which resulted in lactic acid production from glycerol. The effects of pH control and substrate concentration on lactic acid fermentation were also investigated. Glycerol and acetic acid concentrations of 30 g/L and 10 g/L, respectively, were expected to be appropriate for lactic acid fermentation of glycerol by strain QU 11 at a pH of 6.5. Furthermore, fed-batch fermentation with 30 g/L glycerol and 10 g/L acetic acid wholly exhibited the best performance including lactic acid production (55.3 g/L), lactic acid yield (0.991 mol-lactic acid/mol-glycerol), total yield [1.08 mol-(lactic acid and ethanol)]/mol-(glycerol and acetic acid)], and total carbon yield [1.06 C-mol-(lactic acid and ethanol)/C-mol-(glycerol and acetic acid)] of lactic acid and ethanol. In summary, the strain QU 11 successfully produced lactic acid from glycerol with acetic acid metabolism, and an efficient fermentation system was established without carbon loss.
authors.affiliation: Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: n.murakami329@gmail.com.
authors.forename: Nao
authors.initials: N
authors.lastname: Murakami
authors.affiliation: Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: mana.oba.ct@gmail.com.
authors.forename: Mana
authors.initials: M
authors.lastname: Oba
authors.affiliation: Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Iwamoto
authors.affiliation: Laboratory of Soil Microbiology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan; Institute of Advanced Study, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: tashiro@agr.kyushu-u.ac.jp.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Tashiro
authors.affiliation: Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: gucci1448@gmail.com.
authors.forename: Takuya
authors.initials: T
authors.lastname: Noguchi
authors.affiliation: Laboratory of Food Process Engineering, Division of Food Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: 3BE13023G@s.kyushu-u.ac.jp.
authors.forename: Kaori
authors.initials: K
authors.lastname: Bonkohara
authors.affiliation: Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan; Botany and Microbiology Department, Faculty of Science (Boys branch), Al-Azhar University, PN:11884, Nasr City, Cairo, Egypt. Electronic address: mohamedali@kyudai.jp.
authors.forename: Mohamed Ali
authors.initials: MA
authors.lastname: Abdel-Rahman
authors.affiliation: Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: zendo@agr.kyushu-u.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Zendo
authors.affiliation: Laboratory of Food Process Engineering, Division of Food Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: mshimoda@agr.kyushu-u.ac.jp.
authors.forename: Mitsuya
authors.initials: M
authors.lastname: Shimoda
authors.affiliation: Laboratory of Soil Microbiology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: kensak@agr.kyushu-u.ac.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sakai
authors.affiliation: Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan; Laboratory of Functional Food Design, Department of Functional Metabolic Design, Bio-Architecture Center, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. Electronic address: sonomoto@agr.kyushu-u.ac.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sonomoto
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D056804:Biofuels / Q000600:supply & distribution; D002244:Carbon / Q000378:metabolism*; D013293:Enterococcus faecalis / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D005990:Glycerol / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D056804:Biofuels; D019344:Lactic Acid; D000431:Ethanol; D002244:Carbon; D005990:Glycerol; D019342:Acetic Acid
keywords: Acetic acid metabolism; Carbon loss; Enterococcus faecalis; Glycerol; Lactic acid fermentation