Tracking carbon and nitrogen flow in black soldier fly larvae cultivation: Effects of feed carbohydrate-to-protein ratio

Abstract

Production of proteins and lipids using insects, particularly black soldier fly larvae (BSFL), has attracted increasing attention due to their high nutritional value and the sustainability of the rearing process. This study aims to investigate the effects of varying carbohydrate-to-protein ratios in feed formulations on BSFL growth and metabolism. In addition, the distribution of carbon and nitrogen from the feed was calculated to determine how much of each was fixed into BSFL biomass and how much was lost as gaseous emissions. Larval weight increased with higher protein content in the feed. Feed composition also influenced BSFL metabolism, with lower carbohydrate levels leading to reduced lipid content (53.4–35.1 wt%) and increased protein accumulation (20.1–42.6 wt%). While the fatty acid profiles of BSFL remained comparable across groups, their amino acid profiles varied depending on the feed formulations. In particular, a higher protein content in the feeds resulted in elevated essential amino acid profiles in BSFL. The carbohydrate-to-protein ratio in the feed also affected the carbon and nitrogen flow during BSFL cultivation, with the 2:1 ratio (C:N ratio of 11:1) showing the highest allocation rate of carbon and nitrogen into BSFL biomass. These results suggest that fine-tuning the carbohydrate-to-protein ratio in feed formulations can modulate BSFL metabolite profiles toward protein-rich, lipid-rich, or balanced compositions, depending on the intended application. However, such optimization should also account for carbon and nitrogen losses occurring during the bioconversion of organic substrates, including food waste