Garden fruit chafer (Pachnoda sinuata L.) accelerates recycling and bioremediation of animal waste

Bioconversion of livestock wastes using insect larvae represents an emerging and effective strategy for waste management. However, knowledge on the role of the garden fruit chafer (Pachnoda sinuata L.) in waste recycling and influence on the diversity of microbial community in frass fertilizer is limited. Here, we determined whether and to what extent the conversion of cattle dung into insect frass fertilizer by P. sinuata influences the frass’ microbial community and its associated antibiotic resistance genes abundance. Pachnoda sinuata larvae were used to valorise cattle dung into frass fertilizer; samples were collected weekly to determine the composition of bacteria and fungi, and antibiotic resistant genes using molecular tools. Results revealed that bioconversion of cattle dung by P. sinuata larvae significantly increased the richness of beneficial bacteria in the frass fertilizer by 2.5-folds within 28 days, but fungal richness did not vary during the study. Treatment of cattle dung with P. sinuata larvae caused 2 – 3-folds decrease in the genes conferring resistance to commonly used antibiotics such as aminoglycoside, diaminopyrimidine, multidrug, sulfonamide and tetracycline within 14 days. Furthermore, the recycling cattle dung using considerably reduced the abundance of mobile genetic elements known to play critical roles in the horizontal transfer of antibiotic resistance genes between organisms. This study highlights the efficiency of saprohytic insects in recycling animal manure and suppressing manure-borne pathogens in the organic fertilizer products, opening new market opportunities for innovative and safe bio-based products and achieving efficient resource utilization in a circular and green economy.