Biological and Chemical Extraction of Chitin and Chitosan from The Black Soldier Fly (Hermetia illucens) Exoskeleton and Antimicrobial Activity against Selected Human Pathogenic Microbes

Abstract

Globally, the broad-spectrum antimicrobial activity of chitin and chitosan has been widely documented. However, very little research attention has focused on chitin and chitosan extracted from black soldier fly pupal exoskeleton, which are abundantly present as by products from insect-farming enterprises. This study presents the first comparative analysis of chemical and biological extraction of chitin and chitosan from the BSF pupal exoskeleton. The antibacterial activity of chitosan was also evaluated. Traditionally, chitin and chitosan are extracted using chemicals that are both expensive and harmful to the environment. For chemical extraction, demineralization and deproteinization were carried out using 1 M hydrochloric acid at 100°C for 2 h and 1 M NaOH for 4 h at 100°C, respectively. Biological extraction of chitin was carried out by protease-producing bacteria and lactic-acid-producing bacteria for protein and mineral removal, respectively. The extracted chitin was converted to chitosan via deacetylation using 40% NaOH for 8 h at 100°C. Chitin characterization was done using FTIR spectroscopy, while the antimicrobial properties of BSF chitosan were determined using the disc diffusion method. Chemical and biological extraction gave a chitin yield of 10.18% and 11.85%, respectively. A maximum chitosan yield of 6.58% was achieved via chemical treatment. From the FTIR results, biologically and chemically extracted chitin showed characteristic chitin peaks at 1650 and 1550 cm−1 wavenumbers corresponding to amide I stretching and amide II bending, respectively. Scanning electron microscopy revealed that the surface morphologies of biologically extracted chitins consisted of fibers and pores together, while chemically extracted chitins had neither fibers nor pores. There was significant growth inhibition for Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans when subjected to 2.5 and 5 g/ml concentrations of chitosan. This findings demonstrate that chitosan from BSF pupal exoskeleton could be a promising and novel therapeutic agent for drug development against resistant strains of bacteria.