Aspergillus cristatus is a key microorganism involved in the fermentation of Fu brick tea, but systematic strain-level safety data remain limited despite its long history of use in dark tea production. In this study, the toxicological safety of A. cristatus CCNH008 was assessed through acute oral toxicity assay, a 90-day repeated oral toxicity study with a recovery period and genotoxicity assays. In acute oral toxicity tests, CCNH008 caused no mortality, no adverse clinical signs, and no treatment-related effects on bodyweight or pathology in mice or rats, with an LD₅₀ greater than 10 g/kg bodyweight. In the 90-day repeated oral toxicity study in rats, the oral administration of CCNH008 at doses up to 1.67 g/kg bodyweight/day produced no treatment-related changes in clinical signs, bodyweight, food consumption, hematological or biochemical parameters, urinalysis, organ weights, or histopathology, including during a 28-day recovery period. Genotoxicity was evaluated using a bacterial reverse mutation assay, an in vitro mammalian chromosome aberration test, and an in vivo mammalian erythrocyte micronucleus test; no mutagenic or clastogenic effects were observed. Collectively, these findings demonstrate that CCNH008 shows no evidence of acute, subchronic oral toxicity, or genotoxicity, providing important strain-level safety evidence to support its potential application in food-related products.

There were errors in the original publication

The filamentous fungus Aspergillus cristatus is the principal fermentative microorganism that defines the quality of Fuzhuan brick tea (FBT). However, its specific enzymatic repertoire has not been systematically characterized at the genome level, limiting the broader biotechnological deployment of this fungus. Here we combined whole-genome sequencing, comparative genomic profiling against four well-characterized Aspergillus species (Aspergillus niger, Aspergillus oryzae, Aspergillus nidulans, and Aspergillus fumigatus), CAZyme annotation, and an empirical 19-enzyme activity panel benchmarked against a 50-strain Aspergillus reference set to define the enzymatic specificity of A. cristatus strain CCNH008. The 28.1 Mb hybrid assembly was the most compact genome among the five compared species and encoded the smallest CAZyme repertoire of the compared genomes, with a strongly restrained pectinolytic complement. Enzymatic profiling revealed a distinctive phenotype characterized by moderate cellulolytic capacity, marked polyphenol oxidase and protease activities, and a genotype–phenotype discordance in which pectinase activity ranks among the highest in the 50-strain panel despite a limited predicted pectinolytic gene complement. Comparative genomic profiling positioned CCNH008 between the lignocellulose-degrading specialist A. niger and the starch-adapted food fungus A. oryzae, consistent with adaptation to the unique chemical environment of tea leaves. The safety profile was assessed by in silico PHI/DFVF virulence factor screening and in vitro antifungal susceptibility testing. These findings establish a genomic and enzymatic foundation for the rational exploitation of A. cristatus in tea fermentation and related food biotechnology applications.