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Hongkai Guo,Hu Xu,Chengwen Zhao,Xiangzhong Hao,Ziyuan Yang,Weijun Xu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-
Achieving high catalytic performance with the lowest cost possible cathode material is critical for electrocatalyticsynthesis of H2O2 by oxygen reduction reaction. In this work, we describe a method ofpreparing highly active yet stable graphite felt electrocatalysts containing ultrahigh-loading oxygen contentby using organic acid anodic modification. The results show that modified graphite felt surface wasmore hydrophilic and introduced a large amount of defect sites and oxygen-containing groups. Moreover,the influence of mass oxalic/citric acid ratio and oxidation time of graphite felt cathode were investigated. As a result, H2O2 electrogeneration was 1.6 times as much as that of virgin graphite felt counterpart at themass oxalic/citric acid ratio of 2:1 oxidation for 40 min. However, overoxidation also impaired the electricalproduction of H2O2 due to decarboxylation. Finally, the effect of cathode potential and reaction pHon graphite felt cathode was optimized. As for the modified graphite felt, the maximum accumulationrate of H2O2 reached 4.5 mg h1 cm2 at the conditions of 0.85 V (SCE), 0.4 L min1 O2 flow rate andpH = 3. In addition, it kept a stable performance for electrochemical generation of H2O2 during 8 cycles.
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( Xi He ),( Mingjian Luan ),( Ning Han ),( Ting Wang ),( Xiangzhong Zhao ),( Yanyan Yao ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 Journal of microbiology and biotechnology Vol.31 No.4
Lactobacillus kefiranofaciens contains two types of β-galactosidase, LacLM and LacZ, belonging to different glycoside hydrolase families. The difference in function between them has been unclear so far for practical application. In this study, LacLM and LacZ from L. kefiranofaciens ATCC51647 were cloned into constitutive lactobacillal expression vector pMG36e, respectively. Furtherly, pMG36nlacs was constructed from pMG36e-lacs by replacing erythromycin with nisin as selective marker for food-grade expressing systems in Lactobacillus plantarum WCFS1, designated recombinant LacLM and LacZ respectively. The results from hydrolysis of o-nitrophenyl-β-galactopyranoside (ONPG) showed that the β-galactosidases activity of the recombinant LacLM and LacZ was 1460% and 670% higher than that of the original L. kefiranofaciens. Moreover, the lactose hydrolytic activity of recombinant LacLM was higher than that of LacZ in milk. Nevertheless, compare to LacZ, in 25% lactose solution the galacto-oligosaccharides (GOS) production of recombinant LacLM was lower. Therefore, two β-galactopyranosides could play different roles in carbohydrate metabolism of L. kefiranofaciens. In addition, the maximal growth rate of two recombinant strains were evaluated with different temperature level and nisin concentration in fermentation assay for practical purpose. The results displayed that 37oC and 20-40 U/ml nisin were the optimal fermentation conditions for the growth of recombinant β-galactosidase strains. Altogether the food-grade Expression system of recombinant β-galactosidase was feasible for applications in the food and dairy industry.
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