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Hanxing He,Gefei Li,Jiantao Zhang,Jinlong Zhang,Mingyue Luo,Wenkai Hu,Yamin Lin,Ziyu Deng,Zhicheng Liu,Weizhao Chen,Xu Deng 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.5
A genetic approach was proposed to modify the characteristics of Bacillus subtilis strain WB800 (B. subtilis WB800) for selfhealing of concrete cracks. Three genes, namely gerAa which encodes germination receptors activated by L-alanine, tupA which is responsible for the synthesis of teichuronopeptide, and ca which encodes carbonic anhydrase (CA) catalyzing the synthesis of carbonate ion, were separately transformed into WB800. To protect bacterial cells from being squeezed, microspheres were produced with microcrystal cellulose (MCC) before the introduction of bacteria into the specimens. The results showed that the modified B. subtilis expressing GerA achieved 39.9% of germination ratio compared to 17% by the original host cells. With the transformation of tupA, the modified strain demonstrated higher resistance to alkaline environments, tolerating pH as high as 11, while the original strain only tolerated pH 9. The modified strain expressing CA induced more calcium carbonate than the original cells. Energy dispersive spectroscopy (EDS) identified the produced precipitate to be calcite (CaCO3). Moreover, a mathematical model was developed to optimize the influential factors of calcium precipitation process. Finally, based on the above results, an effective self-healing of concrete crack was achieved. This study may provide a promising strategy to improve the efficiency of bacterial self-healing of concrete cracks.
Characterization of a Novel β-Glucosidase-Like Activity from a Soil Metagenome
Chengjian Jiang,Gefei Ma,Shuangxi Li,Tingting Hu,Zhiqun Che,Peihong Shen,Bing Yan,Bo Wu 한국미생물학회 2009 The journal of microbiology Vol.47 No.5
We report the cloning of a novel β-glucosidase-like gene by function-based screening of a metagenomic library from uncultured soil microorganisms. The gene was named bgl1C and has an open reading frame of 1,443 base pairs. It encodes a 481 amino acid polypeptide with a predicted molecular mass of about 57.8 kDa. The deduced amino acid sequence did not show any homology with known β-glucosidases. The putative β-glucosidase gene was subcloned into the pETBlue-2 vector and overexpressed in E. coli Tuner (DE3) pLacІ; the recombinant protein was purified to homogeneity. Functional characterization with a high performance liquid chromatography method demonstrated that the recombinant Bgl1C protein hydrolyzed D-glucosyl-β-(1-4)-D-glucose to glucose. The maximum activity for Bgl1C protein occurred at pH 8.0 and 42°C using p-nitrophenyl-β-D-glucoside as the substrate. A CaCl2 concentration of 1 mM was required for optimal activity. The putative β-glucosidase had an apparent Km value of 0.19 mM, a Vmax value of 4.75 U/mg and a kcat value of 316.7/min under the optimal reaction conditions. The biochemical characterization of Bgl1C has enlarged our understanding of the novel enzymes that can be isolated from the soil metagenome.