Effects of gender and rearing substrate on protein profile of silkworm (Bombyx mori) pupae

The consumption of insects, or entomophagy, is traditionally practiced in many parts of the world (tropical and subtropical countries in Africa, Asia and Latin-America) where more than 2000 edible insect species are collected in the wild up to today. Entomophagy could contributes positively to the environment, health and livelihoods. The environmental benefits of rearing insects for food are mainly founded on the better feed conversion efficiency of insects respect to those of chicken, pork and beef (van Huis, 2013; Jongema, 2014). In addition, insects can be reared on organic side-streams and are reported to emit lower amounts of greenhouse gases and ammonia, requiring significantly less land and water (FAO, 2013). Generally, they were found to be highly nutritious and to represent good sources of proteins, fat, minerals, vitamins, and energy compared to other animal foods (FAO, 2013). On the other hand, in spite of the nutritional interest, the food safety of edible insects has not been extensively studied but due to the increasing interest of insects as new protein source in the last few years, the European Commission asked the European Food Safety Authority (EFSA) to assess safety risks arising from production and consumption of insects as food and feed. On October 2015 EFSA provided an overall conclusion where reported that a specific risk assessment should be performed taking into account the whole production chain from farming to consumption, including the species to raise and the substrate to use as well as the methods for farming and processing (EFSA, 2015). Among edible insects, the silkworm (Bombyx mori) pupae (SWP), which are massively produced as by-products of the sericulture industry, can be suitable candidates because they could be reused as a protein source. SW has been included in the EFSA list of insect species with the biggest potential to be used as food and feed in the EU even if a specific risk assessment should be still performed, including the evaluation of the allergenic potential associated to entomophagy (EFSA, 2015). The aim of this work was to characterize the protein profile of SWP by 1D and 2D-PAGE coupled to mass spectrometry (MS), in order to identify the most abundant spots (relevant from the nutritional point of view) and any gender and/or rearing substrate dependent differences in protein expression. Three different batches of SWP from each gender reared on natural (mulberry leaves) or an artificial patented diet (Cappellozza et al. 2005) were analyzed. Protein extracts were separated by 2D-PAGE (3 technical replicates for each sample), followed by image and statistical analyses (Shapiro Wilks followed by a one-way analysis of variance and Tukey test with p<=0.05). Both most abundant and gender/rearing-dependent differentially expressed proteins were excised to be identified by MS analysis. Around 60 spots were differentially expressed in at least one of the experimental conditions, considering a 3-fold variation threshold. Among these proteins under identification, major proteins are typical SWP's hemolymph proteins, among these differentially expressed ones are gender-specific (e.g. vitellogenin). Another protein included in the most abundant sub-class is the Lipoprotein 11 already known as food allergen (Zhang et al., 2006). This complex proteomic study could improve the state-of-the-art knowledge about edible insects in term of protein content and protein characterization, both for nutritional and safety evaluation purposes. References Cappellozza L., et al. (2005). Applied Entomology and Zoology, 40(3): 405-412. EFSA Scientific Committee (2015). EFSA Journal, 13(10): 4257. FAO (2013), Edible insects: future prospects for food and feed security. Rome: FAO Jongema, Y. (2014). World list of edible insects. Wageningen University, p. 75. Van Huis A. (2013). Annual Review of Entomology, 58(1): 563-583. Zhang J, et al. (2006). J Trop Med, 6:496-498.