Document Type

Honors Thesis

Major

Microbiology

Advisor(s)

Edward Bernard

Committee Members

Andrei Alyokhin, Sally Molloy, Melody Neely, Sharon Tisher

Graduation Year

May 2021

Publication Date

Spring 5-2021

Abstract

Insects are promoted as cost-effective and sustainable protein sources for animal feed. Their utilization may help to avoid a predicted global protein shortage. Black soldier fly (Hermetia illucens) larvae (BSFL) grow on organic wastes, converting these wastes into larval biomass which can fulfill this purpose. Potential benefits of using BSFL to remediate organic wastes include reduction of waste mass and bacterial load, along with the sale of larvae as a protein supplement. BSFL suppress the growth of some Gram-positive and Gram-negative human pathogens in these substrates; though suppression of Bacillus cereus, a spore-forming bacterium that causes food-poisoning, has not been documented. This project focused on Bacillus cereus suppression by BSFL on byproducts (used as growth substrates) of 2 Maine agricultural industries: potatoes and blueberries. Colony counts on B. cereus selective media were higher for larvae fed on potatoes spiked with pathogen than pathogen alone on potatoes after 2 days. After 4 days, an opposite effect was observed, with lower colony counts observed for larvae fed on potato with B. cereus than pathogen alone on potato. PCR analysis of samples from the potato confirmed the detection of B. cereus. Blueberry substrate was not capable of supporting B. cereus as colony counts for all treatments were below the detection threshold after 2 days of larval feeding. While 100% viability was observed for BSFL reared on blueberries, larval weight decreased by an average of 82% with pathogen compared to a 32% decrease without pathogen, indicating that blueberries are not a suitable growth substrate.

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