Chiral amino acids are extensively applied in the pharmaceutical, food, cosmetic, agricultural, and feedstuff industries. The development of synthetic methodologies for optically pure amino acids has been driven by their significant applications. Among the various synthesis methods for the production of chiral amino acids, enzymatic asymmetric synthesis is a unique preparation strategy that shows great potential. This review provides an overview of the reported methods for enzymatic asymmetric synthesis of chiral amino acids, including asymmetric reductive amination of keto acids, asymmetric transfer of an amino group to keto acids, enantioselective addition of ammonia to α,β-unsaturated acids, and aldol condensation of an amino acid to aldehydes.

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Vinegar is one of the most widely used acidic condiments. In recent decades, rapid advances have been made in the area of vinegar research, and the intellectual structure pertaining to this domain has significantly evolved. Thus, it is important that scientists keep abreast of associated developments to ensure an appropriate understanding of this field. To facilitate this current study, a bibliometric analysis method was adopted to visualize the knowledge map of vinegar research based on literature data retrieved from the Web of Science Core Collection (WoSCC) database. In total, 883 original research and review articles from between 1998 and 2019 with 19,663 references were analyzed by CiteSpace. Both a macroscopical sketch and microscopical characterization of the whole knowledge domain were realized. According to the research contents, the main themes that underlie vinegar research can be divided into six categories, that is, microorganisms, substances, health functions, production technologies, adjuvant medicines, and vinegar residues. In addition to the latter analysis, emerging trends and future research foci were predicted. Finally, the evolutionary stage of vinegar research was discerned according to Shneider’s four-stage theory. This review will help scientists to discern the dynamic evolution of vinegar research, as well as highlight areas for future research.

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Fusarium oxysporum f. sp. cucumerinum is a destructive pathogen on cucumber (Cucumis sativus L.) seedlings and the causal organism of crown and root rot of cucumber plants. An isolate of B579, which was identified as Bacillus subtilis by 16S rDNA sequences analysis, was selected from 158 bacteria isolates as the best antagonist against F. oxysporum by dual plate assay. The production of chitinase, b-1, 3-glucanase, siderophores, indole-3-acetic acid (IAA), hydrogen cyanide (HCN), and phosphate solubilization, by B579 were screened with the selected medium by in vitro tests. The cell-free culture filtrate of B579, with a concentration of 20% (v/v), could result in the vacuolation, swelling and lysis of hyphae. Besides, it could blacken, shrunk and hindered the germination of conidia of F. oxysporum at the concentration of C80% (v/v). When applied as inoculants, B579 (10 8 c.f.u. ml -1 ) was able to reduce disease incidence by 73.60%, and promote seedling growth in pot trial studies. The activities of plant defenserelated enzyme, peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) were significantly increased in plants treated with B579. Interestingly, a higher content of IAA, an important plant growth regulator, was detected in B579 treated plants. Furthermore, seed-soaking with B579 exhibited a better biological control effect (Biocontrol effect 73.60%) and plant growth promoting ability (Vigor Index 4,177.53) than root-irrigation (50.88% and 3,575.77, respectively), suggesting the potential use of B579 as a seed-coating agent.

The objective of this work is to investigate the effects of reaction conditions on the synthesis of octenyl succinic anhydride (OSA)-modified starch from waxy corn starch and to study the characteristics of the OSA-modified starch as well as its applications. A mathematical model was developed to investigate the influences of various processing condition factors on the production of the OSA-modified waxy corn starch production and predict the optimum reaction conditions. The maximal degree of substitution (DS) of OSA-modified waxy corn starch (0.0204) was predicted to occur when the starch concentration was 31.2%, the pH was 8.6, the reaction temperature was 33.6 degrees C, and the reaction time was 18.7 h. Repeated reactions for producing OSA-modified waxy corn starch were carried out in a 5 m(3) reactor under the optimized conditions for verification of the model. The characteristics of modified waxy corn starch including infrared spectrum, scanning electron microscopy, and pasting property were tested and emulsification capacity of the OSA-modified starch were evaluated as well.

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