Isolation & characterization of Bacillus cereus strains from edible insect products

Details

Supervisors

Gillis, Annika

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques, à finalité spécialisée

Abstract

enBacillus cereus sensu lato comprises a diverse group of bacterial species sharing highly conserved genomic backgrounds, yet displaying marked differences in appearance, phenotype, and virulence potential. Notably, B. cereus sensu stricto is responsible for foodborne illness through the production of toxins. The remarkable survival mechanisms of this bacteria including spore formation and biofilm development make it a persistent and significant challenge for the food industry. As the protein transition becomes increasingly central to sustainability debates, edible insects have emerged as a promising alternative to conventional protein sources. However, ensuring a product that is simultaneously nutritious, affordable, and microbiologically safe remains complex. The objective of this study was to better understand the microbiological profile and behavior of bacteria, particularly B. cereus, encountered in edible insect-based foods. To this end, a qualitative and quantitative microbiological analysis of bacterial loads was carried out on 19 samples originating from both regulated EU markets and unregulated or artisanal sources. From these samples, 49 B. cereus strains were isolated and subjected to a characterization approach, combining phenotypic analyses including hemolytic activity, temperature growth range, and colony morphology with molecular analyses aimed at detecting toxin-encoding genes and assessing their toxigenic potential. This work was conducted with a dual purpose: to address food safety concerns and to better understand behavior of B. cereus strains. The study revealed a recurring presence of toxin-associated genes, wide temperature growth ranges, and highly variable strain profiles, reflecting both the remarkable diversity within the B. cereus group and the potential virulence of the isolated strains. This work sheds light on the microbiological hazards associated with the foods of tomorrow, while seeking practical solutions to improve production processes and ensure adequate food safety standards.