Biocontrol of postharvest molds from cigar tobacco leaves by Candida tropicalis 2–17: Screening, identification, and efficacy of its volatile organic compounds

Postharvest mold severely threatens the economic value and sensory quality of cigar tobacco, a highly valuable, non-food industrial crop. Traditional direct-contact fungicides often disrupt the microecological and aroma profiles of the leaves. To address this issue, the present study establishes a novel, non-contact bio-fumigation strategy using Candida tropicalis 2–17 to control mold without leaving physical or chemical residues. In vitro assays demonstrated that volatile organic compounds (VOCs) emitted by strain 2–17 significantly inhibited all eight tested molds, achieving a 100% inhibition rate against six of them. Mechanistically, headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS–SPME–GC–MS) identified eight major VOCs, predominantly alcohols and esters. Among these, phenylacetaldehyde exhibited an extremely low minimum inhibitory concentration (MIC) of 0.03 µL/mL against Aspergillus montevidensis , while a distinct synergistic inhibitory effect (FIC = 0.375) was identified between phenethyl alcohol and isoamyl alcohol . Furthermore, in situ validations revealed that 2–17 fumigation reduced the natural mold incidence from 94.98% to 28.27%. Flavoromic and chemical analyses confirmed that this gas–phase treatment preserved the core chemical components of the leaves ( P > 0.05) while favorably modulating specific volatile profiles, such as downregulating the off-flavor (Z/E)-3-Nonen-1-ol (log 2 FC = –4.295) and upregulating D/ L -Fenchone (log 2 FC = +4.710). These findings demonstrate that C. tropicalis 2–17 is a promising biocontrol agent, providing a quality–preserving green technology for the postharvest storage of densely stacked industrial crops. • Candida tropicalis 2–17 effectively inhibits cigar tobacco molds via VOCs. • Fumigation reduced natural mold incidence from 94.98% to 28.27%. • Phenylacetaldehyde showed strong antifungal activity (MIC = 0.03 µL/mL). • Phenethyl alcohol and isoamyl alcohol exhibited synergistic antifungal effects. • Bio-fumigation improved flavor profiles without altering main chemical components.