Insect-based agri-food waste valorization: Agricultural applications and roles of insect gut microbiota

Abstract

Meeting the demands of the growing population requires increased food and feed production, leading to higher levels of agri-food waste. As this type of waste seriously threatens public health and the environment, novel approaches to waste management should be developed. Insects have been proposed as efficient agents for biorefining waste, producing biomass that can be used for commercial products. However, challenges in achieving optimal outcomes and maximizing beneficial results remain. Microbial symbionts associated with insects are known to have a critical role in the development, fitness, and versatility of insects, and as such, they can be utilized as targets for the optimization of agri-food waste insect-based biorefinery systems. This review discusses insect-based biorefineries, focusing on the agricultural applications of edible insects, mainly as animal feed and organic fertilizers. We also describe the interplay between agri-food waste-utilizing insects and associated microbiota and the microbial contribution in enhancing insect growth, development, and involvement in organic waste bioconversion processes. The potential contribution of insect gut microbiota in eliminating pathogens, toxins, and pollutants and microbe-mediated approaches for enhancing insect growth and the bioconversion of organic waste are also discussed. The present review outlines the benefits of using insects in agri-food and organic waste biorefinery systems, describes the roles of insect-associated microbial symbionts in waste bioconversion processes, and highlights the potential of such biorefinery systems in addressing the current agri-food waste-related challenges.

Keywords: Animal feed; Bioconversion; Edible insects; Frass fertilizer; Symbiotic bacteria.

Graphical abstract

Fig. 1

Insect-mediated waste bioconversion to value-added products (i.e., animal feed and biofertilizer) within the concept of sustainable agriculture.

Fig. 2

The benefits of using insect frass and exuviae as a bio-fertilizer for plant growth and protection. The frass of insects, particularly those that feed on biowaste substrates, has been demonstrated to be a rich source of nutrients and beneficial microbiota. When used as fertilizer for plants, it has been shown to promote plant growth. The microbiota present in insect frass includes plant-beneficial microbes that can act as biocontrol agents against plant pathogens. They can also function as bioprotectants that enhance plant tolerance under stress and biostimulants that induce plant resistance.

Fig. 3

The presence of plant biomass-degrading bacteria in the gut of edible insects, the animal-feed species (H. illucens and M. domestica), and the human-food species (A. domesticus and T. molitor).

Fig. 4

Illustration of the different roles of the gut-associated microbiota of the black soldier fly within the agri-food waste biorefinery system.