Green approaches to extract chitin from black soldier fly discards

Abstract

Insects like black soldier fly (BSF) have emerged as a promising source of chitin due to the short life cycle and reduced requirements for land and water requirement as compared to traditional crustacean-based sources. In this project, chitin extraction was carried out from BSF pupal shells or empty cocoons, which are often discarded as waste but contain approximately 23% of chitin by weight. Conventional methods of chitin extraction involve harsh chemical treatments, specifically strong acids like hydrochloric acid (HCl) for demineralization and strong alkali like sodium hydroxide (NaOH) for deproteinization. This project explores a more sustainable approach by replacing HCl with lactic acid (LA) for demineralization, as well as protease enzymes in place of NaOH for the deproteinization step. Comparative analysis revealed that LA achieved a degree of demineralization (DM%) comparable to that of HCl. For the deproteinization step, four types of protease enzymes, namely acidic protease, alkaline protease, bromelain and papain were investigated as candidates. In addition, various mechanical and thermal pretreatment methods, i.e. ball milling, microwave irradiation and autoclave, were applied to the BSF pupal shell powder to improve enzymatic efficacy. Among the four enzymes tested, acidic protease demonstrated the highest degree of deproteinization (DP%). Notably, ball-milling pretreatment on the LA-demineralized powder improved DP% compared to untreated powder, while microwave irradiation was generally more effective than autoclave pretreatment for enhancing enzymatic access. The combination of acidic protease (50 U/mL) treatment on ball milled, and microwave irradiated LA-demineralized powder led to a near-complete deproteinization (approximately 100% DP%), underscoring the viability of this extraction strategy for sustainable recovery of chitin from insect biomass.