Enhancing black soldier fly larval production from sugarcane bagasse through hydrothermal, enzymatic, and microbial treatment

Abstract In response to the urgent demand for environmentally responsible waste management alternatives, insects such as the black soldier fly (BSF) could be cultivated for the bioconversion of rich organic waste into biomass contents rich in fat and protein. Agricultural residues such as sugarcane bagasse is a renewable biomass source that has the potential to augment the inadequate quantity of suitable organic wastes currently available for insect feeding. However, this recalcitrant lignocellulosic material requires pretreatment to improve its digestibility by BSF larvae (BSFL). Hence, in this study, sugarcane bagasse (SB) was steam pretreated followed by biological treatments (enzymatic hydrolysis, microbial bioprocessing and a combination of both) with each feedstock subsequently tested in BSFL rearing trials. From the results it is clear that a combination of thermal and biological pre-treatments was essential to liberate sugar monomers for BSFL utilisation. Lignocellulose treatment using microbes without enzymes was not feasible for BSFL rearing due to limited in-situ cellulase enzyme production. However, enzymatic hydrolysis combined with microbial biotreatment of steam pre-treated bagasse led to a high bioconversion rate (13.4%), and associated increases in crude protein (33%) and fat (28%) contents of the larvae, which implied that this combined treatment was beneficial to BSFL rearing. These findings suggested that BSFL could be raised on lignocellulosic residues, while increases in protein and fat yields may be achieved through further process optimisation.