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Xi Du,Donghuang Wang,Di Yin,Yi Guan,Xiuyun Ye 한국생물공학회 2019 Biotechnology and Bioprocess Engineering Vol.24 No.6
Microbial pectinases are important sources due to the ease of production and unique physicochemical properties. Here, DY2, a strain of Bacillus licheniformis, was identified from 14 strains of bacteria as a pectinaseproducing bacterium with good application potential. Optimized carbon sources of submerged fermentation led to the identification of glucose as an ideal carbon source for activity and production of P-DY2, the pectinase produced by DY2. GC-MS based metabolomics was used to explore metabolic mechanisms mediated by glucose, showing the frustrated TCA cycle is necessary to elevate the activity and production of P-DY2. Decreased activity of α-ketoglutaric dehydrogenase and succinate dehydrogenase of DY2 in glucose-treated samples supports the conclusion that P-DY2 production is the TCA cycle-independent. These results reveal a metabolic mechanism of high-activity pectinase mediated by exogenous glucose. These findings highlight the way to understand metabolic mechanisms and promote pectinase yield through metabolomics approach and metabolic modulation, respectively.
( Guozeng Wang ),( Meng Luo ),( Juan Lin ),( Yun Lin ),( Renxiang Yan ),( Wolfgang R. Streit ),( Xiuyun Ye ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.5
A new α-amylase-encoding gene (amySL3) of glycoside hydrolase (GH) family 13 was identified in soda lake isolate Alkalibacterium sp. SL3. The deduced AmySL3 shares high identities (82-98%) with putative α-amylases from the genus Alkalibacterium, but has low identities (<53%) with functionally characterized counterparts. amySL3 was successfully expressed in Escherichia coli, and the recombinant enzyme (rAmySL3) was purified to electrophoretic homogeneity. The optimal temperature and pH of the activity of the purified rAmySL3 were determined to be 45°C and pH 7.5, respectively. rAmySL3 was found to be extremely halophilic, showing maximal enzyme activity at a nearly saturated concentration of NaCl. Its thermostability was greatly enhanced in the presence of 4 M NaCl, and it was highly stable in 5 M NaCl. Moreover, the enzyme did not require calcium ions for activity, and was strongly resistant to a range of surfactants and hydrophobic organic solvents. The major hydrolysis products of rAmySL3 from soluble starch were maltobiose and maltotriose. The high ratio of acidic amino acids and highly negative electrostatic potential surface might account for the halophilic nature of AmySL3. The extremely halophilic, calcium-independent, and surfactant-resistant properties make AmySL3 a promising candidate enzyme for both basic research and industrial applications.