Green and roasted coffee as novel substrates for kombucha fermentation: Modulation of bioactivity and phenolic profile.

Fermentation of coffee beverages with a symbiotic culture of bacteria and yeast (SCOBY) is an emerging alternative to traditional tea-based kombucha. This study examined the effects of SCOBY fermentation on the chemical composition and bioactivity of infusions prepared from green and roasted beans of Coffea arabica and Coffea canephora. Fermentation for 14 days markedly altered the phenolic profile and enhanced the antioxidant, antidiabetic, anti-inflammatory, and anticholinesterase activities. Green C. canephora showed the highest antidiabetic and neuroprotective potential, while roasted coffees exhibited stronger antioxidant effects. Multivariate analyses (PCA and Pearson correlation) revealed close associations between phenolic transformation, sugar metabolism and biological functions. The results demonstrate that coffee, particularly in its green form, is a promising substrate for SCOBY fermentation and may serve as a basis for developing novel functional beverages with targeted health-promoting properties.