Effects of treatment process on larvae growth performance and nutrient yield during cyanobacteria bioconversion by black soldier fly

Abstract Cyanobacteria blooms, a global environmental problem, have caused serious economic and ecological disasters worldwide. Black soldier fly larvae (BSFL) are known to feed and develop on a wide range of feed sources, which makes the use of BSFL bioconversion promising for harvested cyanobacteria. In this study, cyanobacteria were compounded into feedstock by three different treatments, and then BSFL was placed into the substrates to explore the effect of treatments on BSFL growth performance and nutrient yield. It was found that the alterations in the nutrient composition of the substrate and the content of key compounds (vitamin C and microcystin-LR) caused by different treatments were responsible for the different growth performance of BSFL. Difference in larvae digestive enzyme activities caused by changes in treatment processes and substrate moisture content will ultimately affect the BSFL nutrient production. The larvae stress response to different treatment processes demonstrated that the low moisture content environment has an inhibitory effect on the growth of BSFL, and the harvested cyanobacteria treated by the sun-drying treatment process exhibited less interference on BSFL. Through a brief economic assessment, we conclude that cyanobacteria can only produce benefits with the sun-drying treatment process where the substrate moisture content needs to be maintained at 70-80%, wall-breaking and heating treatment and heating treatment processes showed a deficit due to a higher cost and a lower output. This study provides a reference for promoting the utilization of cyanobacteria and proffer instructive significance for the biotransformation of cyanobacteria by BSFL.