Mannan-rich oligosaccharides from spent coffee grounds using formic acid hydrolysis: production, characterization and its bioactive properties.

This study aimed to develop a simple and efficient method for producing mannan oligosaccharides (MOS) from spent coffee grounds (SCG) and to investigate their structural characteristics and potential health benefits. The SCG used exhibited a high mannan content and low galactan content. Direct hydrolysis with formic acid at 90 °C for 2.5 h efficiently produced MOS. A total of 19.56 g of mannan-rich oligosaccharides with a high sugar purity of 96.8% (designated FACG) was obtained from 100 g of SCG, corresponding to a yield of 60.6%. FACG consisted of 92.07% mannose, 2.96% galactose, and 1.88% glucose, with uniform distribution of short-chain mannan oligosaccharides (M2-M6), accounting for 61.21% of the total sugars. FACG had a degree of polymerization of 9.00 and a molecular weight of 1459 Da. Its backbone was primarily composed of → 4)-β-Manp-(1 → linkages, with branching at O-3 or O-6 by Glcp-(1 → ), Galp-(1 → ), → 3)-β-Glcp-(1→, and → 4)-β-Galp-(1 → . FACG exhibited dose-dependent hydroxyl radical scavenging activity and promoted the growth of Bifidobacterium adolescentis and Lactobacillus acidophilus, highlighting its potential for applications in food and feed industries.