Antimicrobial Activity Of Black Soldier Fly (Hermetia Illucens) Larvae Extracts

Abstract

Black soldier fly (Hermetia illucens) larvae (BSFL) are not only considered as the alternative and sustainable protein source for food but also the powerful reservoir of natural antimicrobial compounds such as antimicrobial peptides (AMPs), lauric acid, chitin, and polysaccharide. Researching and isolating these potential antimicrobial substances are primarily necessary to tackle the urgent problems of abusing in-feed antibiotics and spreading multidrug resistant bacteria which have been threatening human health. Therefore, this study was conducted to figure out the effect of extraction conditions in terms of types of liquid extraction solvents, drying insect methods, extraction solvent removal ways, and the proper resuspending buffers on obtaining antimicrobial compounds and evaluate antimicrobial activity of BSFL extracts against Gram-negative bacteria - Pseudomonas aeruginosa ATCC 9027 (P. aeruginosa ATCC 9027) and Gram positive bacteria - Staphylococcus aureus ATCC 29213 (S. aureus ATCC 29213) by well diffusion test. P. aeruginosa ATCC 9027 was first isolated from the outer ear infection in 1943 by C. P. Hegarty (Mai-Prochnow et al., 2015). S. aureus ATCC 29213 is a common foodborne bacterial strain capable of generating a variety of exotoxins (Soni et al., 2015). Both of those bacteria not only cause diseases in animals, including humans but also are sensitive or even resistant to a wide variety of antimicrobials (WHO, 2017). These days, in laboratory testing, the S. aureus ATCC 29213 and P. aeruginosa ATCC 9027 is used as a standard quality-control strains (Mai-Prochnow et al., 2015; Soni et al., 2015). The antimicrobial activity of BSFL extracts were observed when using aqueous 20% acetic acid as the extraction solvent of a high acid extraction method. Fresh larvae were dried by microwave and oven showed more inhibition zone against two tested bacteria than freeze drying. Moreover, using oven to evaporate the extraction solvent and concentrate the solute reduced the activity of the remaining 20% acetic acid in comparison to freeze drying. The effective resuspending buffer that showed the highest antimicrobial activity of BSFL extract was PBS 1X. The most suitable extraction condition could be potentially applied at industrial scale was using oven in both larvae drying and extraction solvent removal, then resuspended with PBS 1X which produced BSFL extract (15g fresh larvae/ml) against both P. aeruginosa ATCC 9027 and S. aureus ATCC 29213. The study provides data about extraction conditions for further study to obtain better yield of antimicrobial compounds from BSFL.