Bioprospecting Fungi in Mediterranean Fermentations: Functional Insights and Antibacterial Potential

Table olives, particularly traditionally fermented cracked-style green olives, rely on natural microbial activity without chemical debittering, with fungi playing key roles; in contrast, arbutus berry fermentation remains less characterized in terms of microbial functionality. This study investigated the enzymatic and antibacterial potential of fungal isolates from both systems. A total of 84 isolates belonging to Aureobasidium, Candida, Cryptococcus, Saccharomyces, Pichia, Issatchenkia, Torulaspora, and Sporobolomyces were screened for hydrolytic enzymes (pectinases, amylases, cellulases, xylanases, lipases, proteases, tannases, and β-glucosidases) using selective media, and for antibacterial activity against major foodborne pathogens. Isolates from arbutus fermentation showed no relevant enzymatic or antibacterial ability. In contrast, several isolates from olive fermentation exhibited significant functional traits. Aureobasidium pullulans demonstrated broad enzymatic capacity, producing amylases, esterases, and tannases, along with lipid hydrolysis, but also expressed cellulase, pectinase, and protease abilities. Cryptococcus spp. displayed interesting profiles, with low cellulolytic and pectinolytic capacity and higher phenolase, esterase, and lipase capacities. Antibacterial activity was observed exclusively against Gram-positive bacteria, particularly Staphylococcus aureus and Listeria monocytogenes, mainly among Candida membranifaciens, Cryptococcus spp., and A. pullulans. Overall, table olive fermentation isolates showed promising biotechnological potential for food preservation and quality enhancement, whereas arbutus isolates appeared to have limited functional relevance.