Genome-informed characterization and targeted mycotoxin screening of an Aspergillus niger starter candidate for hawk tea solid-state fermentation.

Defined fungal starters can improve the controllability of plant-based solid-state fermentation, but candidate strains require strain-level genomic characterization and condition-specific product screening. We characterized an Aspergillus niger starter candidate used for hawk tea (Machilus rehderi) fermentation by whole-genome sequencing, comparative genomics, functional annotation, secondary-metabolite genome mining, and targeted HPLC-FLD analysis. The 35.98-Mb assembly comprised nine contigs and contained 12,409 protein-coding genes. BUSCO analysis with eurotiales_odb12.2 recovered 98.2% complete markers from the genome. Mean bidirectional ANI values were highest against three A. niger references (98.98-99.09%), and a phylogeny based on 4,547 single-copy orthologues placed the starter within the A. niger lineage with full node support. The genome contained 523 significant CAZyme profile matches involving 495 proteins and 81 antiSMASH-predicted biosynthetic gene-cluster regions. A fumonisin-like similarity record was treated as a genome-level prediction signal. Aflatoxins B1, B2, G1, and G2, ochratoxin A, and zearalenone were not detected in the tested hawk tea batch; the zearalenone result was interpreted cautiously because a positive quality-control response was not confirmed. These data provide a strain-level basis for further controlled validation of this starter candidate.