Analysis of Quality and Microbial Communities of Pu-Erh Tea Through Inoculation Fermentation with Bacillus licheniformis(接种地衣芽孢杆菌发酵的普洱茶品质与微生物群落分析)
摘要
In order to improve the quality of Pu-erh tea through inoculation fermentation, Bacillus licheniformis L1 isolated and identified from Pu-erh tea was inoculated in sterilized or unsterilized sun-dried green tea leaves to develop pure culture fermentation and enhanced fermentation (EF) of Pu-erh tea. The results showed that the mass fraction of tea polyphenols and the mass ratio of five catechins [(+)-catechin(C), (-)-epicatechin-3-gallate(ECG), (-)-epigallocatechin-3-gallate(EGCG), (-)-catechin gallate(CG) and (-)-gallocatechin gallate(GCG)] in tea leaves decreased significantly compared with control group (P<0.05), while the mass fraction of theabrownins increased significantly (P<0.05) after pure culture fermentation. Compared with normal fermentation (NF), the mass fraction of theabrownins [(6.75±0.13)%], thearubigins [(1.04±0.09)%] and soluble sugar [(5.76±0.10)%] in EF were significantly higher (P<0.05), whereas the mass ratio of six catechins were significantly lower (P<0.05), such as CG [(0.39±0.03)mg/g], (-)-epicatechin [(0.86±0.05)mg/g], GCG [(0.20±0.03)mg/g], C [(2.28±0.14)mg/g], (-)-epigallocatechin [(1.69±0.11)mg/g], EGCG [(0.33±0.02)mg/g]. In sensory evaluation for tea infusion, the scores of sweetness (3.33±0.78) and thickness (6.11±0.71) of EF were higher, while the scores of bitterness (1.33±0.50), astringency (0.67±0.50) and acidity (0.33±0.44) were lower. Colorimeter detection showed that the value of a* (25.70±0.68) and b* (77.06±1.07) of tea infusion in EF were higher and the value of L* (71.58±0.83) was lower. Amplicon sequencing of bacterial 16S rRNA and fungal ITS sequences found that B. licheniformis L1 was not always the dominant bacteria in the whole EF process (only 0.2%~0.3% in the middle and late stage of fermentation), the microbial communities in EF were different from those in NF. The relative abundances of Brevibacterium, Blastobotrys adeninivorans and Rogersella griseliniae in EF were significantly higher (P<0.05), and the relati