Lactic Acid Fermented Green Tea with Levilactobacillus brevis Capable of Producing γ-Aminobutyric Acid

Abstract

The antioxidative activity and bioactive compounds content of lactic acid fermented green tea (LFG) fermented with an outstanding GABA-producing strain under optimised fermentation conditions were evaluated. Levilactobacillus strain GTL 79 was isolated from green tea leaves and selected based on acid production, growth potential, catechin resistance, and GABA production to be applied to LFG. Through 16S rRNA gene sequence analysis, the strain was identified as Levilactobacillus brevis. The optimised conditions were defined as fermentation at 37 °C with supplementation of 1% fermentation alcohol, 6% glucose, and 1% MSG and was determined to be most effective in increasing the lactic acid, acetic acid, and GABA content in LFG by 522.20%, 238.72% and 232.52% (or 247.58%), respectively. Initial DPPH scavenging activity of LFG fermented under the optimised conditions was 88.96% and rose to 94.38% by day 5. Polyphenols may contribute to the initial DPPH scavenging activity, while GABA and other bioactive compounds may contribute to the activity thereafter. Consequently, as GABA and other bioactive compounds found in green tea have been reported to have health benefits, future studies may prove that optimally fermented LFG by L. brevis GTL 79 could be useful in the food and health industries.

Evaluation of Bioactive Compounds and Antioxidative Activity of Fermented Green Tea Produced via One- and Two-Step Fermentation

“…The first 3 tests followed methods described by Jin et al [ 14 ], with minor modifications, including basal medium (1% peptone, 1% glucose, 1% ethanol, 1% glycerol, 0.5% yeast extract; adjusted to a final pH of 6.8 by adding 2 M hydrochloric acid) [ 32 ] for the acid production capability test and YPM broth for the growth potential and resistance to green tea catechins tests, with incubation at 30 °C for 72 h to obtain the strains with the highest acid production and growth potential in the presence of fermentation alcohol [ 37 ]. Specific growth rates and lag times were calculated based on the values generated by Bioscreen C (Labsystems, Helsinki, Finland), using spreadsheet software (Excel 2016; Microsoft Co., Redmond, WA, USA) and a mathematical model developed by Baranyi and Roberts [ 38 ].…”

“…For instance, Wang et al [ 13 ] reported that lactic acid fermentation using Lacticaseibacillus paracasei (formerly Lactobacillus paracasei ) enhanced the anti-obesity effect of green tea. Jin et al [ 14 ] also reported that the use of LAB increased the amounts of a variety of bioactive compounds with health-promoting effects in green tea. In the meantime, acetic acid bacteria (AAB)—such as Acetobacter pasteurianus , A. aceti , and A. lovaniensis —have been extensively utilized in the acetic acid fermentation of various food materials.…”

Kombucha Tea—A Double Power of Bioactive Compounds from Tea and Symbiotic Culture of Bacteria and Yeasts (SCOBY)

“…Application of selected Levilactobacillus brevis (formerly Lactobacillus brevis) strain caused significant increase in DPPH activity from 88.96% to 94.38% after the fifth day of fermentation. It is worth noting that the strain was characterized by high production of γ-aminobutyric acid (GABA) and authors concluded that initial DPPH of tea result from the content of polyphenols, while GABA and other bioactive compounds may contribute to the activity of the fermented product [62]. Although some studies indicates that LAB are present in low numbers in the Kombucha.…”

Modulation effects of microorganisms on tea in fermentation

“…After 8 days of fermentation, the antioxidant activity of fermented tea can reach up to 89.69% ( 62 ). And the DPPH scavenging ability of green tea reached 94.38% after fermentation of GABA-producing lactic acid bacteria for 5 days ( 63 ).…”