Objective  Saccharomyces cerevisiae JP2, isolated from naturally fermented loquat, is a yeast strain with good metabolism of malic acidwine mash. To further investigate its intrinsic acid lowering mechanism, whole genome sequencing and genome sequence information analysis were conducted, and possible metabolic pathways of malic acid were analyzed to identify genes that affect acid lowering.

  Method  Based on the Illumina Miseq and PacBio sequencing platforms, second and third generation sequencing techniques were used to sequence the entire genome of S. cerevisiae JP2 and the type strain S. cerevisiae S288c. Bioinformatics methods were used to assemble their sequences, predict their genes, and annotate their functions, while exploring the possible malic acid metabolism pathways of JP2.

  Result  (1) A total of 52 contigs were obtained by assembling the genome of S. cerevisiae JP2, with a total genome size of 11.98 Mbp and a GC content of 38.07%; There is no significant difference in overall genome size and GC content between JP2 and S288c. (2) There are three pathways for JP2 to metabolize malic acid: malic acid → oxaloacetate → pyruvate; malic acid → pyruvate; and malic acid → fumaric acid. The main genes involved are maeA, MDH, and fumC, among which malic acid → oxaloacetate → pyruvate is the main metabolic pathway with the key gene maeA. (3) The simulated fermentation process showed a decrease of 35.8% in malic acid metabolism and key gene expression levels in JP2, with a significant decrease compared to S288c; Compared with S288c, the maeA gene of JP2 was significantly upregulated (P＜0.01), and its relative expression reached 130% of the initial value in the late fermentation stage.

  Conclusion  JP2 exhibits high expression of maeA gene during fruit wine fermentation, significantly improving the efficiency of malic acid degradation. The research results can provide technical support for the study of the acid reducing functional gene of S. cerevisiae JP2 and the development of acid reducing engineering bacteria.