title: Metabolic engineering of a laboratory-evolved Thermobifida fusca muC strain for malic acid production on cellulose and minimal treated lignocellulosic biomass.
abstract: Malic acid is mainly used as an acidulant and taste enhancer in the beverage and food industry. Previously, a mutant strain Thermobifida fusca muC, obtained by adaptive evolution was found to accumulate malic acid on cellulose with low yield. In this study, the malic acid synthesis pathway in T. fusca muC was confirmed to be from phosphoenolpyruvate to oxaloacetate, followed by reduction of oxaloacetate to malate. To increase the yield of malic acid by the muC strain significantly, the carbon flux from pyruvate was redirected to oxaloacetate by expressing an exogenous pyruvate carboxylase (PCx) gene from Corynebacterium glutamicum ATCC 13032 in the chromosome of T. fusca muC-16. The yield of malic acid in the engineered strain muC-16 was increased by 47.9% compared to the parent strain muC. The muC-16 strain was then grown on ∼100 g/L cellulose and the highest titer of malic acid was 62.76 g/L by batch fermentation. T. fusca muC-16 strain converted milled corn stover to malic acid with the highest titer of 21.47 g/L with minimal treatment.
authors.affiliation: National Engineering Laboratory for Cereal Fermentation Technology (NELCF), Jiangnan University, Wuxi, Jiangsu, 214122, China.|School of pharmaceutical science, Jiangnan University, Wuxi, Jiangsu, 214122, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Deng
authors.affiliation: National Engineering Laboratory for Cereal Fermentation Technology (NELCF), Jiangnan University, Wuxi, Jiangsu, 214122, China.|School of pharmaceutical science, Jiangnan University, Wuxi, Jiangsu, 214122, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Mao
authors.affiliation: School of pharmaceutical science, Jiangnan University, Wuxi, Jiangsu, 214122, China.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Zhang
mesh_terms: D039903:Actinobacteria / Q000201:enzymology* / Q000235:genetics; D018533:Biomass; D002482:Cellulose / Q000737:chemistry; D048230:Corynebacterium glutamicum / Q000201:enzymology; D005285:Fermentation; D008031:Lignin / Q000737:chemistry; D008293:Malates / Q000737:chemistry / Q000378:metabolism*; D060847:Metabolic Engineering; D062907:Oxaloacetic Acid / Q000378:metabolism; D010728:Phosphoenolpyruvate / Q000378:metabolism; D011766:Pyruvate Carboxylase / Q000235:genetics / Q000378:metabolism*; D003313:Zea mays / Q000737:chemistry
chemical_list: D008293:Malates; C036909:lignocellulose; D062907:Oxaloacetic Acid; D010728:Phosphoenolpyruvate; C030298:malic acid; D002482:Cellulose; D008031:Lignin; D011766:Pyruvate Carboxylase
keywords: T. fusca; cellulose; malic acid; metabolic engineering; pyruvate carboxylase