Extraction of cellobiose from spent coffee grounds and prebiotic potential of commercial cellobiose

Valorising abundant agro-industrial waste like spent coffee grounds (SCG) is a key goal of the circular bioeconomy, but its potential for producing high-value functional food ingredients remains underexplored compared to its use for biofuels. This thesis developed a novel pathway to produce cellobiose from SCG and assessed the prebiotic potential of commercial cellobiose. A laboratory-scale process was first established using an optimised alkaline pretreatment (4 M NaOH, 40 °C, 24 h), which increased glucan content from 11.6% to 18.9%. Targeted enzymatic hydrolysis with a low-β-glucosidase, endoglucanase-rich cocktail enabled cellobiose accumulation with minimal glucose by-product. The prebiotic potential of cellobiose was evaluated through in vitro batch fermentation with human faecal inocula and a randomised, double-blind, placebo-controlled human trial (n = 37). Cellobiose was well tolerated up to 10 g/day. Although no statistically significant changes in microbiota composition were observed, correlation analysis revealed that cellobiose drives tight, community-level shifts among interconnected butyrate-producing bacteria. This work establishes a proof-of-concept for producing cellobiose from SCG and provides the first comprehensive analysis of its effects on the human gut microbiota. The findings establish a strong foundation for developing cellobiose as a novel prebiotic from a sustainable waste stream.