Sustainable management of Se-rich silkworm residuals by black soldier flies larvae to produce a high nutritional value and accumulate ω-3 PUFA

Waste disposal and utilisation of its important components are pioneering goals for achieving sustainable development and a clean environment. Silkworm pupae (SWP) are considered a by-product of the sericulture industry and may contain a high concentration of selenium (Se) in some regions, making them a potentially hazardous waste posing health risks. This study examined six treatments of Se-rich SWP (0–100%) as a substrate for black soldier fly (BSF) larvae. Growth performance and protein content of BSF larvae were not affected by increasing SWP content. The total fat, mono-, and poly-unsaturated fatty acids in BSF pre-pupae increased with increasing SWP inclusion in the substrate, from P0 (pre-pupae fed control treatment) through P100 (pre-pupae fed 100% SWP treatment), by 18.83, 61.14, and 62.42%, respectively. The results of significance were: (1) BSF pre-pupae did not accumulate Se, maintaining the same amount of Se in their bodies (~0.18 mg/kg); (2) omega-3 fatty acids represented by linolenic acid in BSF increased by 1,223.35% from P0 to P100, with 70.65% recovered from the SWP; (3) valine percentage increased in BSF compared with the percentage of SWP by 25.30%; and (4) BSF larvae were observed reducing SWP waste by more than one-third. BSF larvae can reduce the waste from sericulture industry and exploit the beneficial properties and components of SWP, converting them into safe and highly nutritious products.