一株冠突散囊菌的分离鉴定、基因组成及其枇杷花发酵特性分析

Isolation, identification, gene composition, and fermentation characterization of a Eurotium cristatum strain

摘要:

【背景】冠突散囊菌LYEC03是从陕西泾阳茯砖茶中分离得到的主要发酵菌株。【目的】研究冠突散囊菌LYEC03菌株的基因组信息及其发酵枇杷花产品的特性，从分子水平阐明冠突散囊菌的发酵机制。【方法】应用形态和显微形态观察、ITS序列鉴定、重测序及框架图测序对所分离的菌株LYEC03进行鉴定和基因组信息解析，采用所分离的菌株LYEC03发酵枇杷花，研究冠突散囊菌对枇杷花主要功效成分及抗氧化性能的影响。【结果】陕西泾阳茯砖茶中分离得到的主要发酵菌株LYEC03确定为冠突散囊菌。菌株LYEC03与参考基因组覆盖率高，含有丰富的纤维素酶、蛋白酶、氧化酶和脂肪酶相关基因；基因组相关整体变异较小，其中假设蛋白、碳水化合物激酶、纤维素酶家族糖基水解酶、位点2蛋白酶家族蛋白、多酚氧化酶和谷胱甘肽过氧化物酶等与菌株生长、能量代谢调节、产纤维酶、产蛋白酶和产氧化酶相关的基因发生了变异。菌株LYEC03基因组序列长度30 623 602 bp、GC含量51.70%、编码13 033个基因、编码基因占比55.74%，参与了碳水化合物代谢、氨基酸代谢、外源生物降解代谢、能量代谢、脂质代谢与萜类化合物和聚酮类化合物的代谢等多种物质的代谢途径转化过程。菌株LYEC03生长、主要功效成分含量的变化与总抗氧化活性、2,2-二苯基-1-苦基肼(2,2-diphenyl-1-picrylhydrazine, DPPH)自由基清除率和羟自由基清除率3个抗氧化指标变化一致，均呈现先增加后缓慢降低的趋势。【结论】冠突散囊菌的发酵特性与其基因组纤维素酶、蛋白酶和氧化酶基因的含量丰富密切相关，对冠突散囊菌的基因组信息分析及其发酵特性研究有利于其发酵产品性能的提升，并为其在食品、轻工业及医药等方面的应用提供科学依据。

关键词:茯砖茶;枇杷花;冠突散囊菌;基因组;发酵;抗氧化

Abstract:

[Background] Strain LYEC03 is a major fermentation strain isolated from Fuzhuan tea in Jingyang county, Shaanxi province, China. [Objective] To reveal the genomic information of strain LYEC03 and the fermentation characteristics of the strain for loquat flower products, and clarify the fermentation mechanism of Eurotium cristatum at the molecular level. [Methods] Morphological and microscopic observation, ITS sequence identification, next-generation sequencing, and whole genome sequencing were employed to identify and analyze the genomic information of strain LYEC03. Furthermore, the strain was used to ferment loquat flowers and the effects of the strain on the main functional components and antioxidant properties of loquat flowers were studied.[Results] strain LYEC03 isolated from Fuzhuan tea in Jingyang, Shaanxi was identified as Eurotium cristatum. The genome of strain LYEC03 had a high coverage of the reference genome and contained abundant genes related to cellulase, protease, oxidase, and lipase. The genes associated with bacterial growth, energy metabolism regulation, fiber production, protease production, and oxidase production had undergone mutations, including hypothetical protein, carbohydrate kinase, cellulase family glycosylhydrolase, site-2 protease family protein, polyphenol oxidase, and glutathione peroxidase. The genome sequence of strain LYEC03 had a length of 30 623 602 bp and the GC content of 57.70%, encoding 13 033 genes, among which 55.74% were coding genes and involved in the carbohydrate metabolism, amino acid metabolism, xenobiotics biodegradation and metabolism, energy metabolism, lipid metabolism, and metabolism of terpenoids and polyketides. The growth of strain LYEC03 and the content of its main functional components presented consistent trends (first increasing and then slowly decreasing) with the three antioxidant indicators: total antioxidant activity, DPPH free radical scavenging rate, and hydroxyl free radical scavenging rate. [Conclusion] The fermentation characteristics of E. cristatum were related to the rich cellulase, protease, and oxidase genes in its genome. Probing into the genomic information and fermentation characteristics of E. cristatum will provide a basis for improving the fermentation performance and applying the strain in food, light industry, medicine and other fields in the future.

Key words:Fuzhuan tea;loquat flowers;Eurotium cristatum;genome;fermentation;antioxidant