Chengbao Duan

Active functional microbiota for producing volatile flavors is critical to Chinese baijiu fermentation. Microbial communities correlated with the volatile metabolites are generally explored using DNA-based sequencing and metabolic analysis. However, the active functional microbiota related to the volatile flavor compounds is poorly understood. In this study, an integrated metatranscriptomic and metabolomics analysis was employed to unravel the metabolite profiles comprehensively and the contributing active functional microbiota for flavor generation during Niulanshan baijiu fermentation. A total of 395, 83, and 181 compounds were annotated using untargeted metabolomics, including LC-MS, GC-MS, and HS-SPME-GC-MS, respectively. Significant variances were displayed in the composition of compounds among different time-point samples according to the heatmaps and orthogonal partial least-square discriminant analysis. The correlation between the active microbiota and the volatile flavors was analyzed based on the bidirectional orthogonal partial least squares discriminant analysis (O2PLS-DA) model. Six bacterial genera, including Streptococcus, Lactobacillus, Pediococcus, Campylobacter, Yersinia, and Weissella, and five fungal genera of Talaromyces, Aspergillus, Mixia, Rhizophagus, and Gloeophyllum were identified as the active functional microbiota for producing the volatile flavors. In summary, this study revealed the active functional microbial basis of unique flavor formation and provided novel insights into the optimization of Niulanshan baijiu fermentation.

Sorbicillinoids are a class of structurally diverse hexaketide metabolites with good biological activities. To explore new structural sorbicillinoids and their bioactivities, the marine-derived fungus Acremonium chrysogenum C10 was studied. Three new sorbicillinoid derivatives, acresorbicillinols A–C (1–3), along with five known ones, trichotetronine (4), trichodimerol (5), demethyltrichodimerol (6), trichopyrone (7) and oxosorbicillinol (8), were isolated. The structures of new sorbicillinoids were elucidated by analysis of nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy (HRESIMS). The absolute configurations of compounds 1–3 were determined by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Compound 3 exhibited a strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, with the IC₅₀ value ranging from 11.53 ± 1.53 to 60.29 ± 6.28 μM in 24 h. Additionally, compounds 2 and 3 showed moderate activities against Staphylococcus aureus and Cryptococcus neoformans, with IC₅₀ values of 86.93 ± 1.72 and 69.06 ± 10.50 μM, respectively. The boundary of sorbicillinoid biosynthetic gene cluster in A. chrysogenum was confirmed by transcriptional analysis, and the biosynthetic pathway of compounds 1–8 was also proposed. In summary, our results indicated that A. chrysogenum is an important reservoir of sorbicillinoid derivatives, and compound 3 has the potential for new natural agents in DPPH radical scavenging.