Comparative and functional genomics of yeast Pichia kudriavzevii RWT identify potential genes involved in aflatoxin...

Aflatoxin B1 (AFB1) is a potent mycotoxin that threatens food safety and human health. This study investigated the capacity of yeast isolates to tolerate and detoxify AFB1 and performed genomic characterization of the most active strain. Among several Pichia and Wickerhamomyces isolates, Pichia kudriavzevii RWT exhibited the strongest tolerance, maintaining growth at AFB1 concentrations up to 200 ppb and decontaminating 26.5% of AFB1 within six hours, more than twice the reduction achieved by the next best isolate. In contrast, heat-killed yeast cells showed no significant reduction activity. This suggests that cell wall adsorption alone is insufficient for meaningful AFB1 reduction in this strain and highlights the importance of enzymatic or transporter-mediated mechanisms that require live, metabolically active cells. Whole-genome sequencing of RWT yielded a 10.86 Mb assembly with 5,445 predicted proteins grouped into 4,274 orthologous clusters, sharing 2,448 core clusters with related yeasts but retaining 953 clusters unique to Pichia species. Functional annotation highlighted genes potentially involved in AFB1 detoxification, including predicted cytochrome P450, epoxide hydrolase (LAP2), glutathione-S-transferase (URE2), and the ABC transporter (YCF1), suggesting pathways for AFB1 activation, glutathione conjugation, and vacuolar sequestration. AFB1 treatments were found to increase the gene expression of those key genes involved in AFB1 detoxification. Comparative genomics confirmed that RWT's genome size and core gene content are typical of P. kudriavzevii, while its unique clusters are enriched in membrane transport, stress response, and metal-ion binding functions. These findings position P. kudriavzevii RWT as a promising candidate for biological AFB1 mitigation, providing a genetic basis for its robust detoxification capacity.