Potential use of frass from edible insect Tenebrio molitor for proteases production by solid-state fermentation

Novel, eco-saving and low-cost food sources are a global priority, such as edible insects. This work sets a valorization pathway for frass and Tenebrio molitor adult insects using solid-state fermentation (SSF) to obtain fungal proteases, which are highly used in food, beverages, cosmetics, pharmaceutical and biotechnology industries. Initial screening experiments demonstrated that Aspergillus uvarum MUM 08.01 was the most efficient proteases producer. Small-scale SSF with frass resulted in high proteases activity (65 U g-1), which increased 52% when BSG was mixed with frass (1:1, w/w). The proteases activity attained in this study using only frass or mixed with BSG was superior compared to other activities observed when using agroindustry by-products (such as rapeseed, sunflower, soybean, among others) and other species of Aspergillus genus. The optimal conditions from full factorial design using frass:BSG mixture resulted in 152 U g-1 of proteases activity, which is in full accordance with the value predicted by the model. SSF scale -up with 50 g of frass:BSG increased proteases activity up to 202.2 U g-1. This study presents an innovative utilization of insects' by-products in the field of enzymes production, in full accordance with the circular economy guidelines.