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

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.