In vitro human fecal fermentation of agarooligosaccharides from Gracilaria fisheri

Abstract

Gracilaria fisheri is a species of algae, and contains dietary fibre that can be classified as a functional food ingredient. Agarooligosaccharide production by acid hydrolysis (AOS-A) has been done with 0.5% acetic acid at 130 °C for 180 min, producing a 47.07 ± 3.22% content of mixed oligosaccharides. Agarooligosaccharide production by enzymatic hydrolysis (AOS-E) has been done with β-agarase enzyme at E/S (enzyme per substrate) ratio 0.1 and 40 °C for 48 h, producing 25.42 ± 3.78% content of higher oligosaccharides (DP 10–60) and 34.71 ± 7.00% of oligosaccharides (DP 3–9). The AOS-A process gave a lower yield but a higher purity than AOS-E (13.67% yield with 60.09% purity for decolored AOS-A, and 43.16% yield with 22.24% purity for AOS-E). The effect of AOS on prebiotic properties of fecal batch cultures indicates that algal extract and AOS have potential for use as functional ingredients to boost bifidobacteria. The prebiotic index of algal extract was 0.07, and increased to 0.16 and 0.12 with AOS-A and AOS-E treatments, respectively. SCFAs production increased gradually during the fermentation of AOS-E with acetic, propionic and butyric acids having the highest concentrations of 29.75 ± 0.68, 25.95 ± 0.48, and 23.05 ± 0.15 mM, respectively, at 48 h of fermentation.