title: Adaptive evolution for fast growth on glucose and the effects on the regulation of glucose transport system in Clostridium tyrobutyricum.
abstract: Laboratory adaptive evolution of microorganisms offers the possibility of relating acquired mutations to increased fitness of the organism under the conditions used. By combining a fibrous-bed bioreactor, we successfully developed a simple and valuable adaptive evolution strategy in repeated-batch fermentation mode with high initial substrate concentration and evolved Clostridium tyrobutyricum mutant with significantly improved butyric acid volumetric productivity up to 2.25 g/(L h), which is the highest value in batch fermentation reported so far. Further experiments were conducted to pay attention to glucose transport system in consideration of the high glucose consumption rate resulted from evolution. Complete characterization and comparison of the glucose phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) were carried out in the form of toluene-treated cells and cell-free extracts derived from both C. tyrobutyricum wide-type and mutant, while an alternative glucose transport route that requires glucokinase was confirmed by the phenomena of resistance to the glucose analogue 2-deoxyglucose and ATP-dependent glucose phosphorylation. Our results suggest that C. tyrobutyricum mutant is defective in PTS activity and compensates for this defect with enhanced glucokinase activity, resulting in the efficient uptake and consumption of glucose during the whole metabolism.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009, People's Republic of China.
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
authors.forename: Shuang
authors.initials: S
authors.lastname: Li
authors.forename: Yi
authors.initials: Y
authors.lastname: Hu
authors.forename: Qing
authors.initials: Q
authors.lastname: Xu
authors.forename: He
authors.initials: H
authors.lastname: Huang
mesh_terms: D000220:Adaptation, Biological; D019149:Bioreactors / Q000382:microbiology; D020148:Butyric Acid / Q000378:metabolism; D048014:Clostridium tyrobutyricum / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D019020:Directed Molecular Evolution; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics
chemical_list: D051246:Glucose Transport Proteins, Facilitative; D020148:Butyric Acid; D005947:Glucose