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Central carbon metabolism influences cellulase production in Bacillus licheniformis

Wang, J., Liu, S., Li, Y., Wang, H., Xiao, S., Li, C., Liu, B.
Letters in applied microbiology 2018 v.66 no.1 pp. 49-54
Bacillus licheniformis, NADP (coenzyme), bioenergy, biomass, biosynthesis, carbon, carbon metabolism, cellulose, endo-1,4-beta-glucanase, energy, enzymatic reactions, genes, homologous recombination, malic enzyme, metabolic flux analysis, pentose phosphate cycle, physiological state, quantitative analysis, stable isotopes, tricarboxylic acid cycle
Bacillus licheniformis that can produce cellulase including endo glucanase and glucosidase is an important industrial microbe for cellulose degradation. The purpose of this research was to assess the effect of endo glucanase gene bglC and glucosidase gene bglH on the central metabolic flux in B. licheniformis. bglC and bglH were knocked out using homologous recombination method, respectively, and the corresponding knockout strains were obtained for ¹³C metabolic flux analysis. A significant change was observed in metabolic fluxes after ¹³C metabolic flux ratio analysis. In both of the knockout strains, the increased fluxes of the pentose phosphate pathway and malic enzyme reaction enabled an elevated supply of NADPH which provided enough reducing power for the in vivo synthesis reactions. The fluxes through tricarboxylic acid cycle and anaplerotic reactions increased fast in the two knockout strains, which meant more energy generated. The changed fluxes in central carbon metabolism provided a holistic view of the physiological status in B. licheniformis and possible targets for further strain engineering. SIGNIFICANCE AND IMPACT OF THE STUDY: Cellulase is very important in the field of agriculture and bioenergy because of its degrading effect on cellulosic biomass. This study presented the effect of central carbon metabolism on cellulase production in Bacillus licheniformis. The study also provided a holistic view of the physiological status in B. licheniformis. The shifted metabolism provided a quantitative evaluation of the biosynthesis of cellulase and a priority ranked target list for further strain engineering.