Evidence for microbial-induced transformation of acrylonitrile-butadiene-styrene (ABS) and styrene-acrylonitrile (SAN) polymer blend by plastic-degrading bacteria

Poly(acrylonitrile-butadiene-styrene) (ABS) and styrene-acrylonitrile (SAN) are extensively used in cosmetic and industrial packaging due to their mechanical strength and durability. However, their intrinsic resistance to microbial and enzymatic attack underlies their long-term environmental persistence. To date, there is limited experimental evidence regarding the microbial transformation of ABS/SAN polymers. Here, we investigated whether four previously reported polyethylene-degrading bacterial strains—Comamonas sp., Delftia sp., Stenotrophomonas sp. and Alcaligenes sp.—can grow on an ABS/SAN blend and induce measurable physicochemical modifications. Each strain was incubated for 90 days in a minimal medium containing ABS/SAN as the sole added carbon and energy source. Bacterial growth, viability and polymer modification were assessed by fluorescence microscopy, gravimetric analysis and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). All strains sustained active growth and remained viable throughout incubation. Stenotrophomonas sp. and Delftia sp. exhibited the strongest responses, with approximately 6-fold and 2.5-fold increases in viable cell counts and corresponding mass losses of 2.20% and 1.27%, respectively. ATR-FTIR profiles revealed strain-specific chemical changes on the polymer surface, including reductions in nitrile and carbonyl content consistent with partial oxidation and assimilation of ABS/SAN fragments. Comparative genomic analysis further identified genes encoding putative catabolic functions that may facilitate polymer transformation, such as nitrilases, amidases, phenylacetate and aromatic compound degradation pathways, redox-active enzymes and efflux transporters. Together, these findings provide a novel experimental evidence that select bacterial strains can interact with and induce measurable modifications in ABS/SAN polymer blend, highlighting new perspectives for the biological degradation of recalcitrant synthetic plastics.