Mitigation effects of short-chain fatty acids on microplastic accumulation in plastic-degrading Zophobas morio larvae...

Zophobas morio larvae can actively feed on and digest plastic foam. However, concerns remain about potential microplastic residues in the larvae after plastic degradation, which limited their safe and sustainable use. This study confirmed the accumulation of microplastics in larvae after plastic degradation, and investigates the effects and molecular mechanisms of supplemented short-chain fatty acids (SCFAs) on this process. Py-GCMS analysis suggested that SCFAs significantly inhibited the microplastics accumulation in the gut, fat body and Malpighian tubules of plastic-degrading larvae. Compared with feeding on pure polystyrene, supplementation with SCFAs led to an additional decrease of 3.8 kDa in the number-average molecular weight and 76 kDa in the weight-average molecular weight of polystyrene after larval digestion. Moreover, SCFAs improved fecal morphology in plastic-fed larvae, which was beneficial to intestinal emptying and slowed down the microplastics accumulation in the gut. Moreover, SCFAs mitigated gut damage to protect the intestinal barrier, which suppressing microplastic translocation to other tissues. Specifically, SCFAs protected gut by inhibiting gut pathogenic bacteria and increasing gut immune substances including 11-Deoxy prostaglandin F1β, Prostaglandin K2, and PG(PGF1α/i-21:0). Moreover, SCFAs significantly upregulated genes associated with oxidative stress response and membrane repair and reversed the suppression of C2H2-type domain-containing protein and GH18 domain-containing protein expression caused by plastic ingestion in gut of larvae. This study reveals the risks of microplastic accumulation and transmission in insects during plastic degradation, proposes feasible avoidance strategies, and provides a potential solution for ensuring the safety of the economical reuse of insect larvae after plastic degradation.