Tingting Liu,Matthew Jay Malkmes,Liying Zhu,He Huang,Ling Jiang
Here, Metal-Organic Frameworks (MOFs) coupling simultaneous saccharification and fermentation for butyric acid production using rice straw was constructed. Clostridium tyrobutyricum Δ ack :: cat1 , with deleted ack gene and overexpressed cat1 gene, was used as the butyric-acid-fermentation strain. MOFs was employed as a photocatalyst to improve butyric acid production, as well as a cytoprotective exoskeleton with immobilized cellulase for the hydrolysis of rice straw. Thus, the survival of MOFs-coated strain, the thermostability and pH stability of cellulase both remarkably increased. As a result, 55% of rice straw was hydrolyzed in 24 h, and the final concentration of butyric acid in visible light was increased by 14.23% and 29.16% compared to uncoated and coated strain without visible light, respectively. Finally, 26.25 g/L of butyric acid with a productivity of 0.41 g/L·h in fed-batch fermentation was obtained. This novel process inspires green approach of abundant low-cost feedstocks utilization for chemical production.
Isothiazolones are used as preservatives in various modern industrial products. Although microorganisms that exhibit resistance towards these biocides have been identified, the underlying resistance mechanisms are still unclear. Therefore, we investigated the resistance properties of the following Burkholderia cepacia strains to Kathon (a representative of isothiazolones): a wild-type (WT) strain; a laboratory resistance strain (BC-IR) induced from WT; and an isolated strain (BC-327) screened from industrial contamination samples. The bacterial cell structure was disrupted by 50 μg ml −1 Kathon treatment. BC-IR and BC-327 did not display resistance in the presence of 1 ml L −1 Tween 80, 1 ml L −1 Triton X-100, 0.1 % sodium dodecyl sulfate or 1 mmol L −1 EDTA-2Na. Additionally, BC-IR and BC-327 exhibited lower relative conductivity from 10 to 180 min. The types as well as the levels of outer-membrane proteins (OMPs) were altered among WT, BC-IR and BC-327. Finally, the two Kathon-resistance strains BC-IR and BC-327 presented higher resistance capacity to H 2 O 2 . We measured the levels of peroxide-sensor genes and observed that the transcriptional activator oxyR , superoxide dismutase sod1 , sod2 , catalase cat1 and cat3 were all up-regulated under oxidative conditions for all strains. Taken together, OMPs and peroxide-sensor genes in B. cepacia contributed to isothiazolone resistance; However, the laboratory strain BC-IR exhibited a different resistance mechanism and properties compared to the isolated strain BC-327.
危险品化学品经营许可证（带存储）