Sourdough fermentation supports in vitro eubiotic effects of gluten-free bread fortified by insect flour

Insect powder for food applications has been recently accepted in Europe, but the dietary effects on the human gut microbiome have still to be widely studied in vivo. In this context, personalized gut models may provide robust results for clinical application, reduce time, cost, waste, and animal testing, as the Regulation (EU) 2019/1010 indicates. In this work, a gluten-free (GF) bread fortified with insect protein was considered to gain insights of insect- fortified sourdough bread on the human colon microbiome. Bread prototypes were in vitro tested by coupling Infogest® oro-gastroduodenal digestion to MICODE colon fermentation. The metabolomics and microbiomics profiles of colonic fermentation of baker’s yeast fermented and sourdough-fermented GF breads enriched with insect (Acheta domesticus) powder (IP) were compared to control GF breads. The results were two-pronged and indicated that IP-containing GF sourdough breads might improve some general indicators of colonic community eubiotic status but might also bear some potential insults. In details, the GF sourdough with IP was able to; i) increase some beneficial bacteria (Bifidobacterium spp., Lactobacillus gassseri and L. crispatus); ii) reduce other beneficial bacteria (Akkermansia muciniphila and Bacteroides spp.); iii) limit the growth of opportunistic bacteria (Escherichia albertii and Clostridium perfringens) and iii) reduce the growth of sulfurate producers (Desulfovibrio and Bilophila); iv) produce more organic fatty acids (acetate and butyrate); v) reduce the amount of some harmful compounds (p- cresol); vi) increase speciation of oxidant aldehydes (acetaldehyde and benzeneacetaldehyde). Additionally, acetate, butyrate, and hexanoate were positively expressed in the correlation network plot of insect-enriched breads conversely to controls. These preliminary results carried out by MICODE gut model evidenced that the sourdough process is the best solution to produce IP-fortified GF bread since it supports some potential properties of the final product.