Changes in lipids and medium- and long-chain fatty acids during the spontaneous fermentation of ripened pu-erh tea.

During the fermentation of ripened pu-erh tea (RPT), the composition of lipids and other compounds changes significantly. In this study, we conducted industrial fermentation of RPT and observed that the levels of water extract, tea polyphenols, free amino acids, catechins, caffeine, rutin, theophylline, luteolin, and myricetin decreased, while the level of soluble sugar increased. Additionally, the levels of gallic acid, quercetin, ellagic acid, and kaempferol first increased and then decreased during fermentation. We identified a total of 731 lipids, which were classified into seven categories using a lipomics method. Among these lipids, 85 with relatively high contents decreased, while 201 lipids with low contents increased after fermentation. This led to an overall decrease in the sum contents of lipids and dominant lipids, including glycerophospholipids and saccharolipids. We also detected 33 medium- and long-chain fatty acids, with α-linolenic acid (881.202 ± 12.13-1322.263 ± 19.78 µg/g), palmitic acid (797.275 ± 19.56-955.180 ± 30.49 µg/g), and linoleic acid (539.634 ± 15.551-706.869 ± 12.14 µg/g) being the predominant ones. Coenzymes Q9 (62.76-63.57 µg/g) and Q10 (50.82-59.33 µg/g) were also identified in the fermentation process. Our findings shed light on the changes in lipids during the fermentation of RPT and highlight the potential bio-active compounds, such as α-linolenic acid, linoleic acid, Coenzymes Q9, and Q10, in ripened pu-erh tea. This contributes to a better understanding of the fermentation mechanism for RPT.

Changes in sensory characteristics, chemical composition and microbial succession during fermentation of ancient plants Pu-erh tea.

"Ancient tea plants" are defined as tea trees > 100 years old, or with a trunk diameter > 25 cm; their leaves are manufactured to high - quality, valuable ancient plants pu-erh tea (APPT). In this study, a fermentation of APPT were developed, and outstanding sweetness of APPT infusion was observed. During fermentation, the content of soluble sugars, theabrownins (p < 0.05), as well as 41 metabolites were increased [Variable importance in projection (VIP) > 1.0; p < 0.05 and Fold-change (FC) FC > 2]; While relative levels of 72 metabolites were decreased (VIP > 1.0, p < 0.05 and FC < 0.5. Staphylococcus, Achromobacter, Sphingomonas, Thermomyces, Rasamsonia, Blastobotrys, Aspergillus and Cladosporium were identified as dominant genera, and their relative levels were correlated with contents of characteristic components (p < 0.05). Together, changes in sensory characteristics, chemical composition and microbial succession during APPT fermentation were investigated, and advanced the formation mechanism of its unique quality.

Biosynthetic pathway of prescription bergenin from Bergenia purpurascens and Ardisia japonica.

Bergenin is a typical carbon glycoside and the primary active ingredient in antitussive drugs widely prescribed for central cough inhibition in China. The bergenin extraction industry relies on the medicinal plant species Bergenia purpurascens and Ardisia japonica as their resources. However, the bergenin biosynthetic pathway in plants remains elusive. In this study, we functionally characterized a shikimate dehydrogenase (SDH), two O-methyltransferases (OMTs), and a C-glycosyltransferase (CGT) involved in bergenin synthesis through bioinformatics analysis, heterologous expression, and enzymatic characterization. We found that BpSDH2 catalyzes the two-step dehydrogenation process of shikimic acid to form gallic acid (GA). BpOMT1 and AjOMT1 facilitate the methylation reaction at the 4-OH position of GA, resulting in the formation of 4-O-methyl gallic acid (4-O-Me-GA). AjCGT1 transfers a glucose moiety to C-2 to generate 2-Glucosyl-4-O-methyl gallic acid (2-Glucosyl-4-O-Me-GA). Bergenin production ultimately occurs in acidic conditions or via dehydration catalyzed by plant dehydratases following a ring-closure reaction. This study for the first time uncovered the biosynthetic pathway of bergenin, paving the way to rational production of bergenin in cell factories via synthetic biology strategies.

[Microbial community structure in strong aromatic liquor fermented grains characterized by PLFA fingerprints].

Taking the nine common microbial strains in liquor-making process as test objects, this paper studied the characteristics of phospholipid fatty acid (PLFA), a characteristic component of the strains cell membrane, and the relationships between the detected amount of PLFA and the biomass of the strains. There existed significant differences in the PLFA fingerprints between test bacteria, actinomycetes, molds, and yeasts, and the PLFA fingerprint of each strain could be used as the basis to distinguish species and genus. Within a certain range of the strains biomass, the detected amount of total PLFA or 16:0 was linearly correlated with the biomass. After adding different biomass Gram positive (G+) bacteria, Gram negative (G-) bacteria, and fungi in fermented grains, a significant difference was observed in the relative amount of PLFA between experimental and control samples. It was suggested that the fingerprint of PLFA could quantitatively or semi-quantitatively characterize the microbial community structure and its dynamic variation in fermented grains. By detecting the PLFA profiles of fermented grains in various liquor industries and by analyzing the microbial community structure in the fermented grains, it was substantiated that PLFA fingerprinting was of general applicability.