Extraction, characterization and evaluation of antimicrobial activity of chitosan from adult Zophobas morio (Fabricius, 1776) (Coleoptera: Tenebrionidae)

The increasing demand for chitosan has led to the exploration of alternative sources, including insects. In this study, chitosan was extracted from Zophobas morio beetles with 19.17 % yield. FTIR and Raman Spectroscopy showed similar peaks in Z. morio chitosan (ZC) and commercial chitosan (CC). ZC showed low crystallinity (40.96 %) and high thermal residual mass (42.7 %) than CC. SEM imaging of ZC displayed pores ranging from 10 μm to 0.3 μm. EDX mapping revealed the homogenous presence of C, N and O elements. ZC exhibited low molecular weight (435.95 kDa) and low intrinsic viscosity (317.95 cm³/g) than CC (680.20 kDa and 480.87 cm³/g, respectively). Degree of deacetylation of ZC and CC was 96.24 % and 78.26 %, respectively. ZC showed antimicrobial activity against Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Proteus mirabilis (ATCC 29906), Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212) and Candida albicans (ATCC 90028) with zones of inhibition ranging from 5 mm to 11 mm. The minimum bactericidal concentration of ZC against K. pneumoniae and P. mirabilis was lower than CC. This study suggests the applicability of insect chitosan as an antimicrobial agent in the food and pharmaceutical industries.