Characterisation of <i>Tenebrio molitor</i> Reared on Substrates Supplemented with Chestnut Shell.

Abstract

<i>Tenebrio molitor</i> 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 <i>T. molitor</i> 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% <i>w</i>/<i>w</i> chestnut shell (TRT1), and treatment group two was fed wheat bran supplemented with 25% <i>w</i>/<i>w</i> 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 (<i>p</i> < 0.05). Proteins and lipids of TRT2 were higher than other groups (<i>p</i> < 0.05). Important differences were observed in the amino acid profile of TRT1 and TRT2 compared to CTRL (<i>p</i> < 0.05). TRT1 and TRT2 showed higher <i>E. coli</i> inhibitory activity than CTRL (<i>p</i> < 0.05). In conclusion, chestnut shell supplementation improved the survival and functional characteristics of larvae and likely impacted the insects' metabolism.