Comparative Analysis of Fungal Communities and the Key “Golden-Flower” Fungi in Fu Brick Tea From Seven Chinese Regions and Their Effects on the Quality of Summer-Autumn Tea

Abstract

Fu brick tea (FBT) is a distinctive microbial-fermented dark tea from China; however, systematic studies on its fungal communities and “golden-flower” fungi remain limited. In this study, 52 FBT samples from seven representative regions were analyzed to investigate their fungal community structure and “golden-flower” fungi. High-throughput sequencing revealed Aspergillus as the dominant genus (65.58%–98.85%), followed by Wallemia (0.17%–19.58%) and Candida (0.01%–18.47%). A total of 52 “golden-flower” fungi, one from each sample, were isolated and identified as Aspergillus cristatus based on morphological features, internal transcribed spacer (ITS) sequencing, and multigene phylogenetic analysis (BenA, CaM, and RPB2). Haplotype analysis revealed four distinct haplotypes: Haplotype_1 and Haplotype_3 were shared across all regions, whereas Haplotype_2 and Haplotype_4 were unique to Hunan. Analysis of molecular variance (AMOVA) results indicated that genetic differentiation was primarily attributed to individual differences among strains, with minor divergence among geographical groups. The fastest growing strain from each region was selected to assess its influence on summer-autumn tea quality using non-targeted and targeted metabolomics, along with electronic sensory analysis (electronic eye [E-eye] and electronic tongue [E-tongue]). These strains were found to reduce catechins, flavonols, flavones, and phenolic acids, while increasing polymerized catechins and their derivatives, thereby improving overall flavor. Notably, strains from Shaanxi, Anhui, and Sichuan exhibited superior fermentation performance compared to those from Hunan, Hubei, Guizhou, and Zhejiang. This study provides new insights into the functional characteristics of A. cristatus in FBT, offering a scientific basis for quality improvement and the utilization of microbial resources in dark tea production.