Bioconversion of Organic Wastes by Black Soldier Fly for Chitin, Lipid and Protein Production

Abstract

The bioconversion of organic waste into black soldier fly (BSF) larvae, which is a valuable source of lipid, and protein, is part on an ongoing creative effort in valorising waste. Besides lipid and protein, BSF larvae also contain significant amounts of chitin, a polymer of N-acetylglucosamine that make up the backbone of the polysaccharide structure normally found in insects. In this study, the effects of organic waste type and moisture content on biomass conversion ratio were investigated. BSF larval development (larvae to prepupae to pupae) was found to occur to the highest extent (98.90 ± 0.71 % biomass converted) when kitchen waste (KW) was used compared to when vegetables waste (VW) (84.6 ± 1.41 % biomass converted) or fruit waste (FW) was used (87.5± 0.71 % biomass converted). The optimal moisture content of the kitchen waste was found to be 80 %, which results in the highest waste biomass conversion of 99.8 % ± 0.58. The BSF larvae were found to have approximately 38 – 42 % crude lipid, 34 – 41 % crude protein, and 8 – 9 % ash content. Chitin was isolated through a three-step process of deproteinization, demineralization, and decolorization. A yellowish-grey powder was obtained at the end of the isolation process and the chitin yield was determined to be 4 – 6% (g/g). Fourier transform infra-red (FTIR) analyses confirmed the chitin yield by identifying the -OH, -CH₃CONH, and -CO stretching of its polysaccharides and glucosamine rings; and the lipid yield by noting the disappearance of the hydroxyl stretching that had been present in the spectra of unprocessed BSF larvae, and the appearance of X–H stretching which indicates the presence of triglyceride functional groups.