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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.
Yali Qiao,Cong Leng,Gefei Liu,Yanjiao Zhang,Xuepeng Lv,Hongyu Chen,Jiahui Sun,Zhen Feng 한국미생물학회 2019 The journal of microbiology Vol.57 No.9
Understanding global changes of physiological processes at the molecular level during the growth of Streptococcus thermophilus is essential for the rational design of cultivation media and the optimization of bioprocesses. Transcriptomics and proteomics were combined to investigate the global changes at the transcript and protein level during the growth of S. thermophilus. The expression of 1396 genes (FDR ≤ 0.001) and 876 proteins (P < 0.05) changed significantly over time. The most remarkable growth phase dependent changes occurred in the late-lag phase and were related to heterofermentation, glycolysis, peptidoglycan biosynthesis, conversion between amino acids and stress response. The present results could provide theoretical guidance for high-cell-density culture, help design cultivation media, and help attain a high biomass of S. thermophilus.