Safety evaluation of a β-fructofuranosidase enzyme preparation from Aspergillus fijiensis SYG-K1 for the production of 1-kestose-enriched short-chain fructooligosaccharides

Short-chain fructooligosaccharides (scFOS) are prebiotic food ingredients, and 1-kestose-enriched preparations are of interest because of their defined short-chain composition. This study evaluated a β-fructofuranosidase preparation from Aspergillus fijiensis SYG-K1 developed for 1-kestose-enriched scFOS production. Fermented food-derived microbial isolates were screened for FOS-producing activity, and the selected parental strain was improved by ultraviolet/N-methyl-N′-nitro-N-nitrosoguanidine-induced random mutagenesis. The resulting SYG-K1 strain showed increased β-fructofuranosidase activity and produced a favourable FOS profile with high GF2 formation, limited GF3 formation, and no detectable GF4 formation under the tested conditions. A GLP-compliant toxicological safety package was applied according to appropriate OECD test guidelines, including acute oral toxicity, repeated-dose oral toxicity, and genotoxicity studies. A single oral dose of 2,000 mg/kg produced no toxicity. Repeated oral dose administration of up to 1,643.9 mg total organic solids (TOS)/kg bw/day produced no treatment-related adverse effects or delayed toxicity. The enzyme preparation was negative in bacterial reverse mutation, in vitro chromosomal aberration, in vitro micronucleus, and in vivo micronucleus assays. The NOAEL was established at 1,643.9 mg TOS/kg bw/day, supporting the toxicological safety of this enzyme preparation.