Proteogenomics Study of Blastobotrys adeninivorans TMCC 70007-A Dominant Yeast in the Fermentation Process of Pu-erh Tea

Fungal community composition and function in different Chinese post-fermented teas

Chinese post-fermented teas are produced through special fermentation by microorganisms, with fungi significantly contributing to their flavor and sensory characteristics. Here, the fungal community structure and function were investigated using Illumina HiSeq sequencing of the fungal ITS rDNA region across different post-fermented teas, including Fuzhuan, Qingzhuan, Tianjian black, Liupao, and raw and ripened Pu-erh. Additionally, the headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) technology was used to compare the volatile components of tea samples, and moisture content, pH, total nitrogen, carbon-nitrogen ratio, and total sulfur were measured. All the tea samples were slightly acidic, with pH values of 5.56-6.43, and Ascomycota was the most dominant phylum, representing over 90% of the relative abundance. However, there were significant differences at the genus level in the six typical post-fermented teas. Aspergillus was the most dominant genus in Fuzhuan (91.16%), Qingzhuan (54.89%), Tianjian (64.11%), and Liupao (47.43%) teas, whereas Debaryomyces and Blastobotrys were the most dominant genera in raw (35.67%) and ripened (78.88%) Pu-erh tea, respectively. A functional prediction analysis revealed that most fungal gene functions were involved in metabolism. A total of 26 main volatile components were detected, which differed in composition among six tea samples. This is the first comparative analysis of fungal communities and volatile components in different typical Chinese post-fermented teas, and the results will aid the design of better culturing strategies for the specific dominant fungal species and the influence of fungi on aroma types of post-fermented teas.

Production of single cell protein rich in potassium by Nectaromyces rattus using biogas slurry and molasses

Single-cell protein (SCP) is a vital supplement for animal protein feed. This study utilized biogas slurry and sugarcane molasses to ferment Nectaromyces rattus for the production of SCP. The optimal batch fermentation conditions were obtained in a 5L jar with a tank pressure of 0.1 MPa, an initial speed of 300 rpm, and an inoculum volume of 30%. The highest cell dry weight concentrations of the fed-batch fermentation without reflux and the fed-batch fermentation with reflux were 46.33 g/L and 29.71 g/L, respectively. The nitrogen conversion rates (47.05% and 44.12%) and the cell yields of total organic carbon (1 g/g and 1.17 g/g) of both fermentation modes were compared. The SCP contained 42.32% amino acids. Its high concentrations of potassium (19859.96 mg/kg) and phosphorus (7310.44 mg/kg) present a novel approach for the extraction of these essential nutrients from biogas slurry. The enrichment of K was related to the H+ efflux and sugar transport.

Mapping the human gut mycobiome in middle-aged and elderly adults: multiomics insights and implications for host metabolic health

OBJECTIVE

The human gut fungal community, known as the mycobiome, plays a fundamental role in the gut ecosystem and health. Here we aimed to investigate the determinants and long-term stability of gut mycobiome among middle-aged and elderly adults. We further explored the interplay between gut fungi and bacteria on metabolic health.

DESIGN

The present study included 1244 participants from the Guangzhou Nutrition and Health Study. We characterised the long-term stability and determinants of the human gut mycobiome, especially long-term habitual dietary consumption. The comprehensive multiomics analyses were performed to investigate the ecological links between gut bacteria, fungi and faecal metabolome. Finally, we examined whether the interaction between gut bacteria and fungi could modulate the metabolic risk.

RESULTS

The gut fungal composition was temporally stable and mainly determined by age, long-term habitual diet and host physiological states. Specifically, compared with middle-aged individuals, Blastobotrys and Agaricomycetes spp were depleted, while Malassezia was enriched in the elderly. Dairy consumption was positively associated with Saccharomyces but inversely associated with Candida. Notably, Saccharomycetales spp interacted with gut bacterial diversity to influence insulin resistance. Bidirectional mediation analyses indicated that bacterial function or faecal histidine might causally mediate an impact of Pichia on blood cholesterol.

CONCLUSION

We depict the sociodemographic and dietary determinants of human gut mycobiome in middle-aged and elderly individuals, and further reveal that the gut mycobiome may be closely associated with the host metabolic health through regulating gut bacterial functions and metabolites.

Deep N-terminomics of Mycobacterium tuberculosis H37Rv extensively correct annotated encoding genes

Mycobacterium tuberculosis (MTB) is a severe causing agent of tuberculosis (TB). Although H37Rv, the type strain of M. tuberculosis was sequenced in 1998, annotation errors of encoding genes have been frequently reported in hundreds of papers. This phenomenon is particularly severe at the 5' end of the genes. Here, we applied a TMPP [(N-Succinimidyloxycarbonylmethyl) tris (2,4,6-trimethoxyphenyl) phosphonium bromide] labeling combined with StageTip separating strategy on M. tuberculosis H37Rv to characterize the N-terminal start sites of its annotated encoding genes. Totally, 1047 proteins were identified with 2058 TMPP labeled N-terminal peptides from all the 2625 mass spectrometer (MS) sequenced proteins. Comparative genomics analysis allowed the re-annotation of 43 proteins' N-termini in H37Rv and 762 proteins in Mycobacteriaceae. All revised N-termini start sites were distributed in 5'-UTR of annotated genes due to over-annotation of previous N-terminal initiation codon, especially the ATG. In addition, we identified and verified a novel gene Rv1078A in +3 frame different from the annotated gene Rv1078 in +2 frame. Altogether, our findings contribute to the better understanding of N-terminal of H37Rv and other species from Mycobacteriaceae that can assist future studies on biological study.

Structural Insight into a Yeast Maltase-The BaAG2 from Blastobotrys adeninivorans with Transglycosylating Activity

An early-diverged yeast, Blastobotrys (Arxula) adeninivorans (Ba), has biotechnological potential due to nutritional versatility, temperature tolerance, and production of technologically applicable enzymes. We have biochemically characterized from the Ba type strain (CBS 8244) the GH13-family maltase BaAG2 with efficient transglycosylation activity on maltose. In the current study, transglycosylation of sucrose was studied in detail. The chemical entities of sucrose-derived oligosaccharides were determined using nuclear magnetic resonance. Several potentially prebiotic oligosaccharides with α-1,1, α-1,3, α-1,4, and α-1,6 linkages were disclosed among the products. Trisaccharides isomelezitose, erlose, and theanderose, and disaccharides maltulose and trehalulose were dominant transglycosylation products. To date no structure for yeast maltase has been determined. Structures of the BaAG2 with acarbose and glucose in the active center were solved at 2.12 and 2.13 Å resolution, respectively. BaAG2 exhibited a catalytic domain with a (β/α)₈-barrel fold and Asp216, Glu274, and Asp348 as the catalytic triad. The fairly wide active site cleft contained water channels mediating substrate hydrolysis. Next to the substrate-binding pocket an enlarged space for potential binding of transglycosylation acceptors was identified. The involvement of a Glu (Glu309) at subsite +2 and an Arg (Arg233) at subsite +3 in substrate binding was shown for the first time for α-glucosidases.