title: Systematic Engineering of Escherichia coli for d-Lactate Production from Crude Glycerol.
abstract: Crude glycerol resulting from biodiesel production is an abundant and renewable resource. However, the impurities in crude glycerol usually make microbial fermentation problematic. This issue was addressed by systematic engineering of Escherichia coli for the production of d-lactate from crude glycerol. First, mgsA and the synthetic pathways of undesired products were eliminated in E. coli, rendering the strain capable of homofermentative production of optically pure d-lactate. To direct carbon flux toward d-lactate, the resulting strain was endowed with an enhanced expression of glpD-glpK in the glycerol catabolism and of a heterologous gene encoding d-lactate dehydrogenase. Moreover, the strain was evolved to improve its utilization of cruder glycerol and subsequently equipped with the FocA channel to export intracellular d-lactate. Finally, the fed-batch fermentation with two-phase culturing was carried out with a bioreactor. As a result, the engineered strain enabled production of 105 g/L d-lactate (99.9% optical purity) from 121 g/L crude glycerol at 40 h. The result indicates the feasibility of our approach to engineering E. coli for the crude glycerol-based fermentation.
authors.affiliation: Department of Chemical Engineering, Feng Chia University , 100 Wenhwa Road, Taichung 40724, Taiwan.
authors.forename: Zei Wen
authors.initials: ZW
authors.lastname: Wang
authors.affiliation: Department of Chemical Engineering, Feng Chia University , 100 Wenhwa Road, Taichung 40724, Taiwan.
authors.forename: Mukesh
authors.initials: M
authors.lastname: Saini
authors.affiliation: School of Chinese Medicine, College of Chinese Medicine, China Medical University , Taichung 40402, Taiwan.
authors.forename: Li-Jen
authors.initials: LJ
authors.lastname: Lin
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, China Medical University , No. 91, Hsueh-Shih Road, Taichung 40402, Taiwan.
authors.forename: Chung-Jen
authors.initials: CJ
authors.lastname: Chiang
authors.affiliation: Department of Chemical Engineering, Feng Chia University , 100 Wenhwa Road, Taichung 40724, Taiwan.|Department of Health and Nutrition Biotechnology, Asia University , Taichung 41354, Taiwan.|Department of Medical Research, China Medical University Hospital , Taichung 40447, Taiwan.
authors.forename: Yun-Peng
authors.initials: YP
authors.lastname: Chao
mesh_terms: D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000096:biosynthesis*; D060847:Metabolic Engineering
chemical_list: D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase; D005990:Glycerol
keywords: crude glycerol; d-lactate; fermentation technology; metabolic engineering