Viable and Heat-Resistant Microbiota with Probiotic Potential in Fermented and Non-Fermented Tea Leaves and Brews

TL;DR

This study explores the live bacteria in tea leaves and brews, finding heat-resistant probiotic species like H. coagulans in fermented Pu-erh tea.

Contribution

The study identifies heat-resistant probiotic species in fermented tea brews, particularly highlighting Heyndrickxia coagulans.

Findings

Fully oxidized Pu-erh tea had the highest viable bacterial count.

Heyndrickxia coagulans survived 90 °C brewing and remained viable at 70 °C.

Nine distinct H. coagulans strains were identified across six Pu-erh teas.

Abstract

The live microbiota of tea has not been extensively investigated. This study aimed to identify the live, culturable microbiota from four types of tea with varying oxidation levels, before and after brewing. Tea leaves and brews from oolong and fermented teas were analyzed for total viable counts of aerobic bacteria, lactobacilli, fungi, and Enterobacteriaceae. Cultivation was performed and isolates were identified by Sanger sequencing. Heat resistance was assessed at 70 °C and 90 °C. Random Amplified Polymorphic DNA (RAPD) was used to determine strain-level diversity. Fully oxidized, post-fermented Pu-erh tea had the highest viable bacterial count. Most isolates belonged to Bacillaceae, Staphylococcaceae, and Paenibacillaceae, families associated with soil or human skin. Only two potentially pathogenic species were identified: Staphylococcus epidermidis and Bacillus cereus. In Pu-erh, live bacteria were detected after brewing at 90 °C, including Heyndrickxia coagulans, a spore forming probiotic species. H. coagulans strains remained in vegetative state after hot water exposure and survived at 70 °C, indicating thermotolerance. RAPD-analysis revealed nine distinct H. coagulans strains across six Pu-erh teas. Conclusion: This study provides new insight into the viable microbiota of different teas and their survival during brewing, highlighting safety concerns and probiotic species like H. coagulans.

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