Bioethanol production from edible insect excreta: a case study on frass from house crickets

Abstract

House crickets are among the most promising edible insect species for inclusion in future agri-food systems. Their appeal stems from environmentally sustainable rearing practices, a high nutritional value, and a long history of traditional use as food. Additionally, their rearing produces a byproduct known as frass, which holds potential as a valuable biomaterial. The utilization of house cricket frass as a substrate for bioethanol production was explored. Frass was digested with cellulases at 10% enzyme/dry matter of substrate, 50°C, pH=5, 48 h. This hydrolysis was combined with different treatments, like acidic (1% sulfuric acid) and alkaline (1% sodium hydroxide), and compared to protease treatment (50°C, pH=6.8, 24 h). The production of sugar and free amino proteins reached 30 and 5 g/L, respectively. Several yeast strains, isolated and identified from various organic waste sources, were tested. The fermentation was performed with Saccharomyces cerevisiae for 48 h with frass hydrolysate, pretreated with sulfuric acid, and digested with proteases and cellulases. The addition of molasses at 0‒60 g/L was considered. Sugar consumption exceeded 80%, with ethanol concentrations reaching 12.56 g/L without molasses and 30.57 g/L with the addition of molasses. Cricket frass was utilized as a substrate for bioethanol production, and the process was significantly enhanced by supplementing it with sugar beet molasses.

Keywords

• edible insects
• frass
• hydrolysis
• fermentation
• bioethanol
• biofuel