Abstract
The increasing plastic production causes serious problems in the marine environment, and the main source of plastic waste comes from the fishing and aquaculture industries. Although there have been various efforts to develop aquaculture equipment with marine biodegradable plastics, an urgent need is to develop an assay to evaluate their biodegradation in aquaculture environments. This study focused on evaluating the biodegradation of biomass plastic in recirculating aquaculture systems (RAS) that mimic freshwater, brackish water, and saltwater aquacultures. The methods used to assess biomass plastic biodegradability included changes in physical properties, weight loss, biochemical oxygen demand, and microbial community investigation using poly(butylene succinate-co-adipate) (PBSA) as a model. Scanning electron microscopy studies indicated the erosion on the biomass plastic surface from 1 to 2 days in the RAS tank (salinity, 0-0.5%) harboring Nile tilapia (Oreochromis niloticus). 4',6-Diamidino-2-phenylindole fluorescence microscopy confirmed the presence of the microorganisms on the PBSA surface. The microorganisms in RAS tanks degraded 11.6% of 1 g/L PBSA in 7 days, demonstrating their biodegradation potential. 16S rRNA gene sequencing showed that Pseudomonas plays a major role as an early decomposer in the biodegradation process within 24 h. A multifaceted analytical method that provides sufficient evidence was developed to show that the erosion on the PBSA surface in RAS tanks results from biodegradation. The ability of RAS to control various aquatic environments (pH, salinity, temperature, and bacterial density) makes it suitable for testing the marine biodegradability of biomass plastics for use in aquaculture and fishery industries.