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Journal of Bioscience and Bioengineering
Vol. 119, No.2, 2015; Pages: 153-158


Fed-batch fermentation for enhanced lactic acid production from glucose/xylose mixture without carbon catabolite repression

Mohamed Ali Abdel-Rahman, Yaotian Xiao, Yukihiro Tashiro, Ying Wang, Takeshi Zendo, Kenji Sakai, Kenji Sonomoto

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

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 tol-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

Keywords: Glucose/xylose mixture; l-Lactic acid production; Fed-batch fermentation; Carbon catabolite repression; Enterococcus mundtii QU 25

 

 
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