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Wei Zeng,Bin Zhang,Qi Liu,Guiguang Chen,Zhiqun Liang 한국미생물학회 2019 The journal of microbiology Vol.57 No.4
Poly(β-L-malic acid) (PMA) is a promising polyester formed from L-malate in microbial cells. Malate biosynthesis is crucial for PMA production. Previous studies have shown that the non-oxidative pathway or oxidative pathway (TCA cycle) is the main biosynthetic pathway of malate in most of PMAproducing strains, while the glyoxylate cycle is only a supplementary pathway. In this study, we investigated the effect of exogenous metabolic intermediates and inhibitors of the malate biosynthetic pathway on PMA production by Aureobasidium melanogenum GXZ-6. The results showed that PMA production was stimulated by maleic acid (a fumarase inhibitor) and sodium malonate (a succinate dehydrogenase inhibitor) but inhibited by succinic acid and fumaric acid. This indicated that the TCA cycle might not be the only biosynthetic pathway of malate. In addition, the PMA titer increased by 18.1% upon the addition of glyoxylic acid after 72 h of fermentation, but the PMA titer decreased by 7.5% when itaconic acid (an isocitrate lyase inhibitor) was added, which indicated that malate for PMA production was synthesized significantly via the glyoxylate cycle rather than the TCA cycle. Furthermore, in vitro enzyme activities of the TCA and glyoxylate cycles suggested that the glyoxylate cycle significantly contributed to the PMA production, which is contradictory to what has been reported previously in other PMA-producing A. pullulans.
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Liu Ning,You Fangtian,Ji Chao,Gong Hongkang,Song Qi,Li Jiasen,Liang Chunjun,He Zhiqun 한국물리학회 2021 Current Applied Physics Vol.31 No.-
Perovskite light-emitting diodes (PeLEDs) prepared by the all-solution-process are gradually coming into view due to their low cost and flexible production process. However, the performance of CsPbBr3 device is limited by the high non-radiative recombination losses due to incomplete surface coverage and grain defects. Here a quaternary ammonium salt, tetrabutylammonium hexafluorophosphate (TBA-PF6) was simultaneously introduced into perovskite emission layers (CsPbBr3) and electron transport layer (TPBi (1,3,5-Tris(1-phenyl-1Hbenzimidazol- 2-yl) benzene) dissolved in ethyl acetate). As a result, the morphology and luminescence of CsPbBr3 films were improved, and the energy level of TPBi was more conducive to charge transport. Consequently, the maximum luminance and current efficiency of the modified green-emitting PeLEDs are improved. Furthermore, the optimized device had an operating life of more than 20 min at an initial luminance of 1230 cd/ m2. This work provides a simple and easy method to be scaled up for the development of low-cost all-solutionprocessed PeLEDs.
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Development of a strategy for the screening of α-glucosidase-producing microorganisms
Bo Zhou,Nan Huang,Wei Zeng,Hao Zhang,Guiguang Chen,Zhiqun Liang 한국미생물학회 2020 The journal of microbiology Vol.58 No.2
α-Glucosidase is a crucial enzyme for the production of isomaltooligosaccharide. In this study, a novel method comprising eosin Y (EY) and α-D-methylglucoside (AMG) in glass plates was tested for the primary screening of α-glucosidaseproducing strains. First, α-glucosidase-producing Aspergillus niger strains were selected on plates containing EY and AMG based on transparent zone formation resulting from the solubilization of EY by the hydrolyzed product. Conventional methods that use trypan blue (TB) and p-nitrophenyl-α-Dglucopyranoside (pPNP) as indicators were then compared with the new strategy. The results showed that EY-containing plates provide the advantages of low price and higher specificity for the screening of α-glucosidase-producing strains. We then evaluated the correlation between the hydrolytic activity of α-glucosidase and diffusion distance, and found that good linearity could be established within a 6–75 U/ml enzyme concentration range. Finally, the hydrolytic and transglycosylation activities of α-glucosidase obtained from the target isolates were determined by EY plate assay and 3,5- dinitrosalicylic acid-Saccharomyces cerevisiae assay, respectively. The results showed that the diameter of the transparent zone varied among isolates was positively correlated with α-glucosidase hydrolytic activity, while good linearity could also be established between α-glucosidase transglycosylation activity and non-fermentable reducing sugars content. With this strategy, 7 Aspergillus niger mutants with high yield of α-glucosidase from 200 obvious single colonies on the primary screen plate were obtained.
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Hao Wu,Guiguang Chen,Yaxi Bian,Wei Zeng,Bihong Sun,Zhiqun Liang 한국미생물학회 2017 The journal of microbiology Vol.55 No.6
In this study, a new agar-degrading strain was isolated from soil with agar as a sole carbon source and energy. Based on its morphological, physiological, biochemical characterization and 16S rDNA sequence, the strain was identified as Strep-tomyces lavendulae UN-8. The extracellular agarase activity reached 0.03 U/ml after fermentation in shake flask (250 ml), which was close to other reported non-marine micro-organisms. Furthermore, it is interesting that the growth of UN-8 would be inhibited by glucose (40 g/L) and maltose (40 g/L) with the inhibitory rate of 100% and 70%, respec-tively. Besides, UN-8 could be grown on the solid medium without any nitrogen sources, then the possible nitrogen fix-ation gene nifU was cloned from its genomic DNA. The de-duced amino acid sequence of nifU has high similarity (98%) with nitrogen fixation protein NifU from Streptomyces sp. NRRL S-104 (KJY22454.1) and Streptomyces sp. NRRL F-4428 (KJK52526.1) based on NCBI blast. It is suggested that the nifU gene of UN-8 also encoded nitrogen fixation protein NifU. These results provided some new information for the further understanding of agar-degrading strain.
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