Screening of flavor-enhancing yeast and its role in fig fermentation

Figs (Ficus carica L.) are rich in sugars and bound aroma precursors that can be converted into aroma compounds.

In this study, the W-8 strain was isolated from fig epidermis and identified as Torulaspora delbrueckii by 26S rDNA sequencing. By optimizing fermentation conditions using single-factor experiments and an orthogonal design, aroma compound (AC) production was evaluated. The whole genome of strain W-8 was sequenced and annotated.

AC production was 1.64 times that of the control. Isoamyl alcohol (0.264 mg/mL), phenethyl alcohol (0.053 mg/mL), isoamyl acetate (0.006 mg/mL), isobutyric acid (0.012 mg/mL), and 2-methylbutyric acid (0.004 mg/mL) were exclusively produced, and production of ethyl stearate and acetoin was increased by 4.20-fold and 2.30-fold, respectively. Strain W-8 harbors a complete genome of 9,224,546 bp. KEGG analysis showed prominent representation of amino acid and carbohydrate metabolism pathways, while GO annotation indicated enrichment in catalytic and metabolic processes. CAZy analysis identified key carbohydrate-active enzymes, including β-glucosidase.

Genome analysis showed that T. delbrueckii W-8 possesses β-glucosidases and aroma-related metabolic pathways, providing a genetic basis for the release of bound aroma precursors from fig substrates and their conversion into AC. These findings highlight T. delbrueckii W-8 as a promising starter for enhancing aroma quality in fermented fig products.