Biowaste and by-products as rearing substrates for black soldier fly (Hermetia illucens) larvae: Effects on larval body composition and performance

Abstract

Black soldier fly (Hermetia illucens) larvae can convert biowaste and by-products into body mass high in protein (~40% dry matter, DM) and lipid (~30% DM). However, the type of rearing substrate also affects the larval body composition and thus its nutritional value. Hitherto, it remains unclear how and to what extent the larval body composition can be altered by the substrate. This study was therefore performed to examine the possibilities of modifying larval body composition using different rearing substrates. To investigate this, 5-days old larvae were reared for seven days on different locally available waste and by-products: brewer’s spent grain, mitigation mussels (Mytilus edulis), rapeseed cake, and shrimp waste meal (Pandalus borealis). Larval composition and performance were compared to larvae reared on a commercial chicken feed as well as a mixed feed (mixture of chicken feed and by-products, with a similar macronutrient composition to chicken feed). Larval body weight was recorded daily to determine growth over time whereas larvae and substrates were sampled at the start and end of the trial and analysed for their nutritional composition. The type of rearing substrate affected both larval body composition and growth performance. There was a clear relation between the nutritional composition of the substrate and larvae for certain fatty acids. Larvae reared on marine-based waste substrates contained a higher share of omega-3 fatty acids than larvae reared on the other substrates, indicating an accumulation of omega-3 fatty acids from the substrate. There was a strong positive linear correlation between the ash content in the substrate and larvae whereas larval lipid, protein, amino acid, and chitin content seemed more affected by larval development. Overall, this study showed that the rearing substrate affects larval composition and development, and that larval composition of certain nutrients can be tailored depending on further food and feed applications.

Bioconversion of Different Waste Streams of Animal and Vegetal Origin and Manure by Black Soldier Fly Larvae Hermetia illucens L. (Diptera: Stratiomyidae)

“…The CP content of the substrate may not necessarily determine the larval CP. Furthermore, the presence of chitin and other non-protein nitrogen-containing compounds (e.g., nucleic acids, uric acid, urea, and ammonia) may result in an overestimation of the crude protein content in BSF when using the standard nitrogen-to-protein conversion factor of 6.25 [ 42 ] and FFW probably had more non-protein nitrogen so the larvae could not store protein.…”

“…Therefore, the growth and the development level of the larvae may also affect their CP accumulation. In addition, Eggink [ 42 ] concluded that the larval composition is affected by the rearing substrate but mostly due to differences in larval development, as reflected in the growth rate, rather than directly reflecting the substrate composition. However, this conclusion is not yet studied enough and only Liu [ 40 ] has tackled this topic.…”

Genetic diversity and organic waste degrading capacity of Hermetia illucens from the evergreen forest of the Equatorial Choco lowland

“…Feeding larvae with optimal food quality composed of a 21% protein to 21% carbohydrate ratio will ensure growth and cycle development ( Cammack & Tomberlin, 2017 ; Dortmans et al, 2017 ). Several studies have highlighted that substrate composition alters the H. illucens lifecycle, survival, nutritional composition, and feed conversion ( Barragan-Fonseca, Dicke & Van Loon, 2018 ; Surendra et al, 2020 ; Laganaro, Bahrndorff & Eriksen, 2021 ; Eggink et al, 2022 ). Thus, the MP-waste substrate did not provide an adequate diet to complete the insect cycle and development.…”

Lauric Acid from the Black Soldier Fly (Hermetia illucens) and Its Potential Applications

“…The discrepancy may be explained by differences in the nutritional composition of the substrates, particularly the digestible carbohydrate content [47]. The high carbohydrate content in the substrate can increase the LA content in BSF larvae or prepupae, as BSF can metabolize carbohydrates into LA within its body biomass [7,20,54]. Previous research by Eggink et al [54] found no LA content in the substrate, indicating that BSF metabolizes carbohydrates through its biosynthetic pathway rather than accumulating LA from the substrate.…”

“…This research indicates that the nutritional content of BSF larvae is influenced by the stage of development, emphasizing the importance of considering the larvae's age at harvest. Moreover, it is possible to modify the specific nutritional composition of BSF larvae to suit the requirements of various applications [54].…”