Pretreatment is an important method for increasing the conversion efficiency of rice straw by black soldier fly larvae based on the function of gut microorganisms.

Rice straw is considered as a renewable biomass energy source and its efficient utilization is still a topic worthy of attention. Black soldier fly larvae, Hermetia illucens (L.), (Diptera: Stratiomydiae) is a kind of saprophytic insect, which can effectively digest organic wastes. Here we report that alkaline peroxide-pretreatment improves the digestion of rice straw by these larvae, especially the decomposition of cellulose, which was at 70.9% compared to 58.2% without pretreatment. After conversion, the effective conversion rates of rice straw to larvae were 10.7% and 11.4%, for raw rice straw and rice straw with pretreatment, respectively. With pretreatment the composition of larval gut microorganisms was altered where Actinomyces, Dysgonomonas, Devosia and Pelagibacterium were the dominant flora for digesting rice straw. In addition, metabolism, environmental information processing and genetic information processing were the major gut microbial functions. These findings demonstrate that chemical pretreatment for the removal of lignin and hemicellulose was an effective measure for the digestion and consumption of rice straw by black soldier fly larvae.