Genomic and transcriptomic analyses identify three new citrate transporters in Pichia fermentans with potential for citric acid reduction in fruit wines

Abstract

Excess citric acid accumulation in fruit wines, particularly those made from kiwi fruit and citrus, contributes to high acidity, adversely impacting sensory properties such as taste balance and consumer acceptance. In this study, Pichia fermentans JT-1-3, a non-Saccharomyces yeast capable of efficiently metabolizing citric acid, was investigated through whole-genome sequencing and transcriptomic analysis. The genome of P. fermentans JT-1-3 was assembled into 15 contigs (12.14 Mb) and annotated with 7728 protein-coding genes. Transcriptome analysis revealed metabolic adaptations in P. fermentans JT-1-3 and identified three putative citric acid transporters (contig1.236, contig1.237, and contig1.238). The expression of these predicted genes was upregulated in response to citric acid, as confirmed by quantitative reverse transcription PCR (RT-qPCR). Fluorescence microscopy confirmed the localization of the three candidate proteins to the plasma membrane. Bioinformatic analysis further revealed their sequence homology and predicted secondary structures. These findings establish a molecular foundation for optimizing P. fermentans as a fermentation adjunct to modulate acidity in fruit wines, thereby enhancing product quality and broadening its potential application in the wine industry.