Natural Food Macromolecule Research Center, School of Food Science and Engineering, Shaanxi University of Science and Technology, Xi'an 710021, PR China; Shaanxi Research Institute of Agricultural Products Processing Technology, Xi'an 710021, PR China.
Natural Food Macromolecule Research Center, School of Food Science and Engineering, Shaanxi University of Science and Technology, Xi'an 710021, PR China.
Food Res Int. 2023 Oct;172:113115. doi: 10.1016/j.foodres.2023.113115. Epub 2023 Jun 15.
Liquid-state fermentation (LSF) of tea leaves is a promising way to obtain tea-based nutraceutical products rich in various bioactive compounds. In the study, the changes of bioactive compounds, tea pigments and complex metabolites from LSF of primary dark tea, green tea and white tea infusions with Aspergillus cristatus were determined. Chemical analyses revealed that soluble sugars, monosaccharide composition, total polyphenols, total flavonoids, free amino acids, soluble proteins and tea pigments were changed in different ways. An untargeted metabolomic analysis and ribonucleic acid sequencing (RNA-seq) based transcriptomic analysis were performed to investigate the metabolic differentiation and clarify the key differentially expressed genes (DEGs, fold change >2 and p < 0.05), showing that amino acid metabolism, carbohydrate metabolism and lipid metabolism were the most enriched pathways during A. cristatus fermentation of primary dark tea, green tea and white tea infusions. In addition, glycerophospholipid metabolism, linoleic acid metabolism and phenylalanine metabolism were greatly accumulated in the fermentation of primary dark tea and white tea infusions; Pyruvate metabolism, glycolysis/gluconeogenesis, fatty acid degradation, tyrosine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis and valine and leucine, isoleucine degradation were greatly accumulated in the fermentation of primary dark tea and green tea infusions; Starch and sucrose metabolism was greatly accumulated in the fermentation of green tea and white tea infusions; Galactose metabolism was significantly enhanced in the fermentation of primary dark tea infusion; Amino sugar and nucleotide sugar metabolism, sphingolipid metabolism and alanine, aspartate and glutamate metabolism were significantly enhanced in the fermentation of green tea infusion. Besides, some other pathways involving aminobenzoate degradation, biosynthesis of cofactors, pyrimidine metabolism, benzoxazinoid biosynthesis and phenazine biosynthesis, tropane, piperidine and pyridine alkaloid biosynthesis and flavone and flavonol biosynthesis also differed from each other. These findings support that A. cristatus plays a vital role in the biochemical and genetic regulation of metabolite profile, and could be considered a potential prospect for better use of A. cristatus on different kinds of tea materials.
液态发酵（LSF）茶叶是获得富含各种生物活性化合物的茶类营养保健品的有前途的方法。在这项研究中，确定了曲霉属曲霉菌对原黑茶、绿茶和白茶汤进行液态发酵时生物活性化合物、茶色素和复杂代谢物的变化。化学分析表明，可溶性糖、单糖组成、总多酚、总黄酮、游离氨基酸、可溶性蛋白质和茶色素的变化方式不同。进行了非靶向代谢组学分析和基于核糖核酸测序（RNA-seq）的转录组学分析，以研究代谢差异，并阐明关键差异表达基因（DEG，倍数变化>2 和 p<0.05），表明在曲霉属曲霉菌发酵原黑茶、绿茶和白茶汤过程中，氨基酸代谢、碳水化合物代谢和脂质代谢是最丰富的途径。此外，甘油磷脂代谢、亚油酸代谢和苯丙氨酸代谢在原黑茶和白茶汤的发酵过程中大量积累；丙酮酸代谢、糖酵解/糖异生、脂肪酸降解、酪氨酸代谢、苯丙氨酸、酪氨酸和色氨酸生物合成以及缬氨酸和亮氨酸、异亮氨酸降解在原黑茶和绿茶汤的发酵过程中大量积累；淀粉和蔗糖代谢在绿茶和白茶汤的发酵过程中大量积累；半乳糖代谢在原黑茶汤的发酵过程中显著增强；氨基糖和核苷酸糖代谢、鞘脂代谢和丙氨酸、天冬氨酸和谷氨酸代谢在绿茶汤的发酵过程中显著增强。此外，还涉及氨基苯甲酸降解、辅因子生物合成、嘧啶代谢、苯并恶嗪生物合成和苯并嗪生物合成、托烷、哌啶和吡啶生物碱生物合成以及黄酮和黄烷醇生物合成的其他一些途径也有所不同。这些发现支持曲霉属曲霉菌在代谢物谱的生化和遗传调控中发挥着重要作用，并且可以被认为是更好地利用曲霉属曲霉菌对不同种类的茶材料的潜在前景。
