Characterisation of Tenebrio molitor Reared on Substrates Supplemented with Chestnut Shell.

Abstract

Tenebrio molitor larvae represent a sustainable protein source for food and feed. The aim of this study was to evaluate the supplementation of chestnut shell, a by-product of the agro-industrial chain, in growth substrates for T. molitor larvae rearing. Seven-week-old larvae were reared on three different growth substrates: the control group (CTRL) was fed wheat bran, treatment group one was fed wheat bran supplemented with 12.5% w/w chestnut shell (TRT1), and treatment group two was fed wheat bran supplemented with 25% w/w chestnut shell (TRT2). Larval weight, substrate consumption, and mortality were recorded weekly. After 14 days, insect meals were produced for bromatological and colorimetric analysis, and bacterial inhibition activity assay using a microdilution method. The amino acid profile of insects was determined using quantitative nuclear magnetic resonance spectroscopy. Our results showed a lower feed conversion ratio and higher larval survival rate % in TRT2 compared to CTRL (p < 0.05). Proteins and lipids of TRT2 were higher than other groups (p < 0.05). Important differences were observed in the amino acid profile of TRT1 and TRT2 compared to CTRL (p < 0.05). TRT1 and TRT2 showed higher E. coli inhibitory activity than CTRL (p < 0.05). In conclusion, chestnut shell supplementation improved the survival and functional characteristics of larvae and likely impacted the insects' metabolism.