Assessment of the nutritional value and functional potential of several flour fractions produced from black soldier fly larvae (Hermetia illucens) in the diet of rainbow trout (Oncorhynchus mykiss)

The aquaculture sector has seen growing expansion since the 1950s in order to meet the increasing demand of the consumer market. The development of this industry also leads to a high demand for raw materials to feed the farmed fish. Fishmeal is currently used massively because it exhibits characteristics adapted to the nutritional needs of fish. It is produced from forage species from reduction fisheries or from bycatch. This is one of the major problems of this sector, which currently does not operate within a logic that is neither sustainable nor ecological. It therefore appears necessary to develop alternative sources of animal protein to replace fishmeal. Since July 2017, the use of seven insect species in aquaculture feed has been authorized. This is notably the case for Hermetia illucens, which is a species capable of efficiently converting a wide variety of organic matter into biomass, and particularly plant organic matter.

It is in this context that this CIFRE thesis project was born, framed by a tripartite collaboration bringing together an industrial partner, the company Innovafeed created in 2016, which is one of the leaders in the insect meal production market using the species Hermetia illucens, a Joint Research Unit (UMR) specializing in the nutrition and metabolism of farmed fish (UMR 1419 NuMéA, INRAE), and the PhyPAQ team of the UMR BOREA developing “omics” approaches on teleost fish and cephalopods.

The objective of this thesis is to evaluate the nutritional value and functional potential of several flour fractions produced from black soldier fly larvae (Hermetia illucens), with the aim of quickly obtaining direct applications in fish farming. The model fish species chosen for this study will be rainbow trout (Oncorhynchus mykiss), which, with over 35,000 tonnes produced annually, constitutes the primary farmed fish species in France.

Organization of Research Work

• Step n°1: characterize the insect meal using transcriptomic/proteomic/peptidomic omics approaches and biochemical approaches
• Step n°2: identify bioactive peptides by coupling separation techniques (rpHPLC) with in vitro functional tests (bioassays) that are myotropic and antibacterial.
• Step n°3: evaluate the nutritional value of the meal fractions: measurement of digestibility, growth trial (body composition, histology of intestinal villi, expression profile of certain intestinal genes (RNAseq), composition of the intestinal microbiota (metabarcoding), determination of the myotropic potential of the feed, evaluation of feed palatability (behavioral approach, DanioVision and EthoVision XT Noldus)