Mycotoxicological and genomic safety assessment of Aspergillus oryzae strain RCAM 01134 – producer of metabolites valuable for the food industry

This article presents the results of a comprehensive safety study of the Aspergillus oryzae RCAM 01134 industrial strain, used in food biotechnology as a producer of acid proteinases, peptidases, and other hydrolytic enzymes. Whole-genome sequencing methods were used to perform taxonomic identification, analyze secondary metabolite biosynthesis genes (including the aflatoxin cluster), and detect allergenicity and antibiotic resistance determinants. The genome assembly comprised 37.5 million base pairs with a BUSCO completeness of 99.4%. Phylogenetic analysis of the β-tubulin gene BenA and calculation of the average nucleotide similarity (ANI 99.3%) confirmed the strain's affiliation with the species A. oryzae, closely related to A. flavus. A degraded cluster of aflatoxin biosynthesis genes with nonfunctional key genes norA, norB, and avfA (structural mutations, reading frameshifts) was identified in the genome. The absence of 11 controlled mycotoxins (aflatoxins B1, B2, G1, G2, sterigmatocystin, ochratoxin A, zearalenone, T-2 toxin, deoxynivalenol, fumonisins B1 and B2) in the culture fluid was experimentally confirmed. All values were below the detection limits (0.001–0.300 mg/kg), which is significantly below hygienic standards. Homologues of A. oryzae allergen genes (over 80% identity) were detected, characteristic of the species and posing a potential risk to sensitized individuals. Genes conferring antibiotic resistance to clinically significant drugs were absent. The authors demonstrated that deep enzymatic bioconversion of mycelial biomass using the strain's own hydrolases leads to the hydrolysis of native allergenic proteins into low-molecular-weight peptides and free amino acids (molecular weight less than 1.6 kDa), significantly reducing the allergenicity of the final products. The A. oryzae strain RCAM 01134 is recommended for industrial use in food processing as safe with respect to toxin formation, with mandatory allergenicity monitoring at the production stage and consumer information.