Use of chitin and krill in aquaculture - the effect on gut microbiota and the immune system: a review

Chitin consists of beta-1,4-linked N-acetylglucosamine residues and is estimated as the second most abundant biomass in the world after cellulose. However, relatively little chitin is utilized as a material for industrial, agricultural and medical applications and aquacultural purposes. Chitin may be useful as a constitutive material in formulated fish feed, and the interesting effects in fish merit further evaluation. There is evidence that fish and aquatic animals harbour a gut bacterial community that is distinctly different from that reported in the surrounding habitat or in the diet. Thus, the gut environment provides a specific niche, and bacterial activity in the gut is not merely a continuum of that observed in the environment. Today, it is well accepted that the gut microbiota in fish are modulated by dietary manipulations. But to what extent can dietary chitin and krill (chitin-rich) modulate the intestinal microbiota of fish and how do these dietary components affect the immune system? These questions will be discussed in the present review.