Differential microbial degradation of cross-linked Polythene by Aspergillus niger in space and on the ground

The microbiological degradation of cross-linked polyethylene (PEX) by Aspergillus niger (A. niger) was simultaneously investigated through a 90-day flight experiment and a ground test. It was the first time to compare materials biodegradation in the China Space Station (CSS) with that on the ground. To this end, we examined the effect of microgravity on A. niger and its further effect on PEX degradation by conducting morphological observations, metabolic characterisations, and chemical structural analyses. Unlike the ground environment, A. niger exhibited enhanced biological activity and growth morphology in the space environment, which led to the secretion of higher levels of organic acids. This caused more extensive damage to the PEX surface structure through the acidic hydrolysis of ester groups. However, changes in the volume resistivity of PEX were not significant when comparing the results from space with those from the ground. This outcome suggests that biodegradation was confined to the surface and did not penetrate deeply during the experiment period.