title: Fed-batch fermentation for enhanced lactic acid production from glucose/xylose mixture without carbon catabolite repression.
abstract: There has been tremendous growth in the production of optically pure l-lactic acid from lignocellulose-derived sugars. In this study, Enterococcus mundtii QU 25 was used to ferment a glucose/xylose mixture to l-lactic acid. Maintenance of the xylose concentration at greater than 10 g/L achieved homo-lactic acid fermentation and reduced the formation of byproducts. Furthermore, carbon catabolite repression (CCR) was avoided by maintaining the glucose concentration below 25 g/L; therefore, initial concentrations of 25 g/L glucose and 50 g/L xylose were selected. Supplementation with 5 g/L yeast extract enhanced the maximum xylose consumption rate and consequently increased lactic acid production and productivity. Finally, a 129 g/L lactic acid without byproducts was obtained with a maximum lactic acid productivity of 5.60 g/(L·h) in fed-batch fermentation with feeding a glucose/xylose mixture using ammonium hydroxide as the neutralizing agent. These results indicate a potential for lactic acid production from glucose and xylose as the main components of lignocellulosic biomasses.
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), Al-Azhar University, Nasr City PN:11884, 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: vacrite@hotmail.com.
authors.forename: Yaotian
authors.initials: Y
authors.lastname: Xiao
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: wangyingcqu@gmail.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
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 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: D064753:Ammonium Hydroxide; D018533:Biomass; D019149:Bioreactors; D057465:Catabolite Repression / Q000187:drug effects; D016983:Enterococcus / Q000201:enzymology / Q000378:metabolism*; D005285:Fermentation / Q000187:drug effects; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D019344:Lactic Acid / Q000096:biosynthesis*; D009584:Nitrogen / Q000378:metabolism / Q000494:pharmacology; D014994:Xylose / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D019344:Lactic Acid; D064753:Ammonium Hydroxide; D014994:Xylose; D005947:Glucose; D009584:Nitrogen
keywords: Carbon catabolite repression; Enterococcus mundtii QU 25; Fed-batch fermentation; Glucose/xylose mixture; l-Lactic acid production