Determination of antibacterial properties and chemical composition of pyrolysis liquid from feeding wastes of mealworm Tenebrio molitor L. (Coleoptera: Tenebrionidae) adults and larvae Scientific paper

Abstract

This study aimed to evaluate the antibacterial properties and phytochemical composition of pyrolysis liquids obtained from the biowaste of the mealworm Tenebrio molitor L. (Coleoptera: Tenebrionidae) adults and larvae. Biowaste was subjected to pyrolysis at 295 ± 5 °C for 7 h under a nitrogen atmosphere using a laboratory-scale system equipped with a dual condensation unit to separate light and heavy fractions. The biowaste pyrolysis liquid (BPL) were purified and analysed for their chemical content using LC-MS/MS, which identified seven key phenolic compounds, with cinnamic acid being the most abundant (358.05 µg/g), followed by salicylic acid, 4-hydroxybenzoic acid, and naringenin. Notably, the most of flavonoid derivatives were either absent or below detection limits, indicating the extract’s phenolic acid-dominated profile. The antibacterial activity of BPL was assessed against two gram-negative (E. coli ATCC-25922, P. aeruginosa ATCC-27853) and two gram-positive (E. faecalis ATCC-23212, S. aureus ATCC-25923) bacterial strains using the agar well diffusion method. The results demonstrated significant antibacterial effects, particularly against S. aureus (29.5 ± 0.3 mm) and P. aeruginosa (23.5 ± 0.2 mm), followed by E. coli (21.7 ± 0.1 mm). These findings highlight the potential of insect-derived pyrolysis liquids as natural antibacterial agents, driven largely by their phenolic acid content. This study underscores the value of biowaste valorisation for developing bioactive compounds with potential applications in antimicrobial therapies.