부산대학교 도서관

Formation of exopolysaccharides (EPS) during 2,3-butanediol (2,3-BD) fermentation by Paenibacillus polymyxa increases medium viscosity, which in turn, presents considerable technical and economic challenges to 2,3-BD downstream processing. To eliminate EPS production during 2,3-BD fermentation, we used homologous recombination to disable the EPS biosynthetic pathway in P. polymyxa. The levansucrase gene which encodes levansucrase, the major enzyme responsible for EPS biosynthesis in P. polymyxa, was successfully disrupted. The P. polymyxa levansucrase null mutant produced 2.5 ± 0.1 and 1.2 ± 0.2 g/L EPS on sucrose and glucose, respectively, whereas the wildtype produced 21.7 ± 2.5 and 3.1 ± 0.0 g/L EPS on the same substrates, respectively. These levels of EPS translate to 8.7- and 2.6-fold decreases in EPS formation by the levansucrase null mutant on sucrose and glucose, respectively, relative to the wildtype, with no significant reduction in 2,3-BD production. Inactivation of EPS biosynthesis led to considerable increase in growth. On glucose and sucrose, the cell biomass of the levansucrase null mutant (8.1 ± 0.8 and 6.5 ± 0.3 g/L) increased 1.4-fold, when compared to the wild type (6.0 ± 0.1 and 4.6 ± 0.3 g/L) grown on the same substrates. Evaluation of the genetic stability of the levansucrase null mutant showed that it remained genetically stable over fifty generations, with no observable decrease in growth or 2,3-BD formation, with or without antibiotic supplementation. Hence, the P. polymyxa levansucrase null mutant has potential for use as an industrial biocatalyst for cost effective large scale 2,3-BD fermentation process, devoid of EPS-related challenges. [ABSTRACT FROM AUTHOR]