Biocontrol of Cheese Spoilage Moulds Using Native Yeasts.

Biocontrol is one of the most promising alternatives to chemical preservatives for food preservation. This study investigated the biocontrol potential of yeasts isolated from raw milk cheese against spoilage moulds. Eighty-four native yeast strains were screened for antagonistic activity against , , and via confrontation using a milk-based culture medium. Fifteen strains from the species , , , and exhibited significant antagonistic activity (inhibition zone > 2 mm) against and . The modelling of the impact of ripening conditions revealed that temperature was the primary factor influencing yeast antagonism. In addition, notable variability at both species and strain levels was found. The antagonist activity was associated with different mechanisms depending on the species and strains. stood out for its proteolytic activity and competition for iron and manganese. Additionally, two strains of this species (KL890 and KL904) were found to produce volatile organic compounds with antifungal properties (phenylethyl alcohol and 1-butanol-3-methyl propionate). GC663 exhibited strong competition for space, as well as the ability to parasitise hyphae linked to its pectinase and β-glucanase activity. The latter enzymatic activity was detected in all strains, with PJ433 standing out due to its proteolytic activity. In a cheese matrix, the efficacy of eight yeast strains against three target moulds was assessed, highlighting the potential of GC663 and PJ433 as biocontrol agents, exhibiting high and moderate efficacy, respectively, in controlling the growth of and . Nonetheless, further research is necessary to elucidate their full spectrum of antifungal mechanisms and to validate their performance under industrial-scale conditions, including their impact on cheese quality.