Bioprospection of Metschnikowia species as a biocontrol agent against AFB1 contamination

Mycotoxin contamination in the food chain poses serious risks to human and animal health, and aflatoxin B1 (AFB1) is the most toxic and carcinogenic compound Advanced strategies for mycotoxin mitigation emphasize biological control using non-pathogenic microorganisms. This study presents the first report of isolating Metschnikowia pulcherrima in Pakistan and its novel application as a biocontrol agent against AFB1. Three strains of M. pulcherrima, pak2 (MW341425), pak3 (MW341426), and pak4 (MW341427), were isolated from fruits (apple, orange, guava, and grape) using the dilution plate technique and evaluated for AFB1-binding potential using whole cells, cell walls, and glucan extracts. From a 100mL culture, 400 mg of yeast biomass produced 35 mg glucan and 5 mg chitin (cell wall proxy). AFB1 was produced and purified from Aspergillus flavus and quantified by HPLC. Binding assays were conducted by incubating 140ppb AFB1 with yeast components at 25 °C under agitation (200 rpm) for 0.5, 1, and 2 h. The highest AFB1 binding was achieved by M. pulcherrima pak3 whole cells (77.37 ± 1.48%) after 1 h Interaction time. Glucan extracts from M. pulcherrima pak3 and M. pulcherrima pak4 showed strong binding (74.99 ± 2.14) within 1-2 h of interaction. However, cell wall fractions showed lower efficacy as compared to glucan component. The cell wall of M. pulcherrima pak4 showed maximum binding (54.28 ± 2.86%) after 2 h. Results indicate that M. pulcherrima, particularly its whole cells and glucan components, effectively bind AFB1 in In-vitro assay suggesting its potential as a natural AFB1 mitigation tool in food and feed. This work highlights the importance of indigenous yeast strains in enhancing food safety.