Co-supplementation of a polyethylene diet for improved fitness of Galleria mellonella larvae

A growing number of plastivore insects have been discovered that readily consume and biodegrade various petro plastics, including LDPE. The caterpillar larvae of Galleria mellonella are capable of breaking down the polymers at expedited rates; however, feeding on LDPE as a sole nutrient source is inefficient and detrimentally impacts larval survival, growth, and development. The objective of our study was to improve fitness parameters and feeding activities of LDPE-fed larvae through the addition of various macro- and micronutrients. Each co-supplementation recovered fitness and consumption to some extent in comparison to pure LDPE; however, artificial sources produced outcomes that were well below those of the caterpillar's natural diet, regardless of the combination. Co-supplementation of LDPE, honeycomb, and corn syrup was the most successful, with larval fitness and consumption approximating their natural diet. To provide mechanistic insights into this recovery, qPCR and metagenomics analyses indicated the co-supplementation promoted greater gut bacterial abundance and species richness and evenness. In addition, GC-MS analyses identified notable differences in their fat body metabolic profiles that may contribute to slower developmental rates. We also assessed the capability of the larvae to eliminate food wastes, which showed promise and could represent a potential co-supplement source for LDPE biodegradation.