Zalerion maritimum and Nia vibrissa potential for expanded polystyrene (EPS) biodegradation

Expanded polystyrene (EPS) is among the most demanded plastic commodities due to its attractive properties of lightness and durability. Such desirable characteristics present, however, an environmental threat, as it is easily transported until it reaches the ocean, where it is likely to be fragmented into microplastics. Despite the efforts for EPS waste management, sustainable and efficient solutions are needed. Biotechnology-based solutions have been investigated for their potential. Herein, Zalerion maritimum and Nia vibrissa were screened for their potential in the biodegradation of EPS, based on the quantified mass differences in both the fungus and the microplastic pellets. In a preliminary evaluation, the highest removal percentage obtained by Z. maritimum, in 28 days, was 66% and the lowest was 25%. In a second assay, the removal percentages were lower. An optimization assay, using Central composite design (CCD), was conducted to obtain optimum values for EPS concentration, pellet dimension and malt extract concentration. These were, respectively, 0.1458 g/L, 1-1.40mm and 20 g/L. Although Z. maritimum showed ability to degrade EPS, the process appeared to be variable and required high amounts of malt extract. Therefore, N. vibrissa was screened for its potential also. In a preliminary assay, N. vibrissa achieved higher microplastic removal percentages. Consequently, a biodegradation assay in optimized medium was conducted. However, the best removal percentage obtained was of 47±16%.