In vitro fermentation and prebiotic potential of selected extracts from seaweeds and mushrooms

• Important impact of water-based enzyme-assisted extracts on gut microbial ecology.
• All extracts influenced gut microbiota numbers and activity albeit at distinct levels.
• Stimulatory effect on Bifidobacterium spp by Pholiota nameko and Osmundea pinnatifida extracts at 1%.
• No significant changes on lactobacilli by the four extracts tested at 1%.
• Selective increase in bifidobacteria, total short chain fatty acids and lactic acid uphold prebiotic activity.

Extracts with prebiotic activity or bioactive compounds from natural sources such as seaweeds or mushrooms, combining a broad spectrum of biological properties, may offer great potential for their use as functional ingredients enabling intestinal microbiota modulation. In this context, selected enzymatic extracts from Sargassum muticum, Osmundea pinnatifida and Pholiota nameko were evaluated in vitro. Faecal fermentations were conducted anaerobically under controlled temperature and pH over 24 h. Enzymatic extracts of Ph. nameko and of O. pinnatifida at 1% (w/v), lead to increases in Bifidobacterium spp. after 6 h of fermentation in comparison to negative control, suggesting a stimulatory effect. No significant changes over 24 h were observed of Lactobacillus spp. In particular, the Ph. nameko extract obtained with Flavourzyme not only stimulated growth and/or activity of Bifidobacterium spp. but also led to a decrease of Clostridium histolyticum group upon 24 h, thus potentially benefiting colonic health. Higher percentages of this extract (2 and 3%) impaired a C. histolyticum reduction confirming this selective action and prebiotic potential. Differences in short chain fatty acids (SCFA) and lactic acid production between the four extracts may indicate a potential relationship between their physico-chemical properties, which differ in composition and structures, and modulation of gut bacterial species.