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Author ORCID Identifier

0009-0003-9504-7599

Abstract

Green tea extract (GTE) is widely recognised for its bioactive compounds, which exhibit potential health benefits, including modulation of gut microbiota. However, the concentration-dependent effects of GTE on specific probiotic strains remain underexplored. The aim of this study was to systematically evaluate the concentration-dependent effects of green tea extract (GTE) on Lacticaseibacillus rhamnosus (L. rhamnosus). The promoting and inhibiting effects of GTE in the range of 0–50 mg/mL were analysed in vitro by OD₆₀₀ growth curve, pH change and colony forming unit (CFU) count. The experimental results showed that the concentration range of 0.05–2.05 mg/mL in the low concentration group significantly promoted bacterial growth and metabolism, and some concentrations (such as 1.65 and 2.05 mg/mL) also showed a typical biphasic or multiphasic growth pattern; while at a concentration of 2.45–3.25 mg/mL, although OD₆₀₀ still showed a certain degree of growth, the CFU count was zero and the pH did not change, indicating that the cells had lost their activity at this stage, and the increase in the growth curve may only reflect cell remnants or sublethal stress responses. Therefore, the minimum bactericidal concentration (MBC) limit is estimated to be between 2.05–2.45 mg/mL. The high concentration group (≥25 mg/mL) showed a significant antibacterial effect; it is worth noting that the OD₆₀₀ curve at the specific concentration of 30 mg/mL was continuously higher than that of the control group, showing an abnormal growth promotion trend. The possibility of this phenomenon is that at a specific concentration, GTE may enhance adaptability by serving as a substrate for bacterial metabolism or by inducing stress response, thereby promoting the growth of L. rhamnosus. In addition, a two-way ANOVA results showed that there was a significant interaction between GTE concentration and culture time (p < 0.001), further supporting its concentration-dependent bidirectional regulation mechanism. The research results provide new in vitro data support for the synergistic mechanism of GTE and probiotics, which is of reference significance for the development of functional foods and symbiotic preparations.

Creative Commons License

Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.

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