# Red Yeast Rice-Driven Kombucha Fermentation: A Novel Strategy for Developing Functional Beverages with Enhanced Hypoglycemic and Hypolipidemic Properties

## TL;DR

This study explores using red yeast rice in kombucha fermentation to create a functional beverage with improved blood sugar and cholesterol-lowering properties.

## Contribution

The novel use of red yeast rice in kombucha fermentation enhances functional properties like hypoglycemic and hypolipidemic effects.

## Key findings

- KRY showed the highest enzyme inhibition rates for hypoglycemic and hypolipidemic activities.
- KRY contained 7 key volatile flavor compounds that improved sensory qualities like aroma and clarity.
- Microbial communities like Komagataeibacter and Saccharomyces correlated with flavor and functional properties.

## Abstract

To address the limited functional diversity of traditional kombucha, this study utilized red yeast rice (RYR) as an alternative substrate and prepared three samples: black tea kombucha (KBT), black tea-red yeast rice mixed kombucha (KBL, at a 1:1 ratio), and red yeast rice kombucha (KRY). After 9 days of fermentation, KRY exhibited the lowest pH, the highest total acidity, and notable sugar metabolic activity. It exhibited in vitro inhibition rates of 82.8%, 78.2%, 70.3%, and 76.9% against cholesterol esterase, pancreatic lipase, α-glucosidase, and α-amylase, respectively, indicating potential hypoglycemic and hypolipidemic activities. In contrast, KBT maintained the strongest antioxidant capacity, with scavenging rates exceeding 90% against both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS). A total of 72 volatile flavor compounds (VFCs) were identified, with 7 key compounds enriched in KRY, which enhanced its sensory acceptance and received the highest scores in color, clarity, and aroma. Microbial community analysis revealed the post-fermentation dominance of Komagataeibacter, Acetobacter, and Saccharomyces, which correlated positively with key VFCs. These findings indicate that RYR as a substrate enhances functional microbial growth, sugar metabolism, organic acid production, flavor enrichment, and in vitro inhibitory activity of enzymes associated with hypoglycemic and hypolipidemic effects.