Effects of feed and probiotic bacteria on Tenebrio molitor performance and entomopathogen susceptibility

Summary

Most mass reared insect can be exposed to entomopathogens with risk of infections, while the impact will depend notably on the environmental conditions, the nutritional feed quality and the microbiota composition of the insects. The yellow mealworm, Tenebrio molitor, is an edible insect mainly reared on cereal-based diets and other agricultural by-products, which can potentially expose the insect to fungal or bacterial entomopathogens as Bacillus thuringiensis (Btt) or Metarhizium brunneum.

In this thesis the evaluation on the impact of insect feed quality and the addition of probiotics on larval growth and susceptibility to the two entomopathogens were addressed by mimicking the mass rearing environment. Results highlight direct correlation between larval body mass and entomopathogen susceptibility, larvae of higher mass being less susceptible. Bacterial probiotic provision has been proposed as possibility for enhancing the resistance against entomopathogens by competing for space and nutrients in the insect gut or by triggering insects’ metabolic or immune pathways.

The impact of probiotic provision was therefore observed on the yellow mealworm bacterial microbiota composition, survival, and weight gain after entomopathogen exposure. Overall, one probiotic specie presented a protective action against pathogens infection. Also, the feed composition and probiotic addition can influence larval growth and the protein and lipid composition of the larva. Overall, the provision of the probiotic strain resulted in larvae with FAMEs profiles characterized by an increment in MUFAs and PUFAs, highlighting the possibility to obtain larvae with a fatty acid profile that is nutritionally more favorable for humans and animals.

Reading this work can give you an overview on the state of art of probiotics applications in insect mass rearing and future perspectives on detection techniques for preserving insect health and mitigating risks of pathogens infection.