Responses of the human gut microbiota to physiologically digested insect powders or isolated chitin thereof

Abstract

As part of the quest for sustainable food choices, edible insects draw increasing attention. Nevertheless, not enough is known regarding their digestive fate and specifically little is known on the colonic fermentability of edible insects or chitin, which is found in many insects or crustaceans. This study interrogated the properties and fermentability of powders from crickets (Acheta domestica), silkworm pupae (Bombyx mori) or isolated chitin. This was done following their in vitro oral, gastric and intestinal digestion and subsequent fermentation in anaerobic bioreactors inoculated with human feces from 10 healthy volunteers. Specifically, each fecal sample was split into 5-parallel anerobic reactors fed with insect samples and fructooligosaccharides or negative control. These were sampled after 0, 5, 10 and 24 h and subjected to 16S rRNA gene sequencing and GC–MS determination of short-chain fatty acids. First, we show colloidal characteristics delineate the static in vitro digestibility of samples and the properties of effluents reaching the colon. Colonic fermentations reveal chitin significantly (p<0.05) supported an increase in biodiversity measures (e.g., alpha diversity using the Shannon index) more than whole insect powders but without any pronounced fluctuations in the production of short-chain fatty acids. Specific analyses further highlight that chitin may be partially responsible for this observation and that its isolated form may induce the growth of symbionts like members of the Ruminococcaceae and Lachnospiraceae families and the genera Faecalibacterium and Roseburia. Overall, this study suggests that chitin from insects may be a potential novel prebiotic, however further research is needed to ascertain this notion.

Keywords

• Edible insects
• Chitin
• In vitro digestion
• Gut microbiota
• Anaerobic colonic fermentation
• Short-chain fatty acids