Investigation of biofilm formation on polyethylene in a diesel/biodiesel fuel storage environment

Biodiesel usage as in the environment as an alternative to fossil fuels or in biodiesel/diesel blends requires an understanding of the potential effects of its addition on the integrity of the infrastructure used for fuel storage. Polyethylene is one of the most common materials for the manufacturing of fuel storage tanks. Due to the insoluble nature of polyethylene, biofilm formation on its surface boosted by the presence of biodiesel could potentially contribute to its degradation. In this study, the effect of biodiesel concentration on biofilm development on linear low-density polyethylene (LLDPE), cross-linked polyethylene (XLPE) and a bilayer construction of linear-low density polyethylene and polyamide-11 (LLDPE/PA) was studied. Polymers were exposed to biodeterioration conditions during a 200days in a simulated fuel storage tank. Excess of water and blends of diesel/biodiesel (0%, 25%, 50%, 75% and 100%) as a carbon source were employed to simulate the conditions found in the bottom of fuel storage tanks, where the presence of water is common as result of condensation. Microorganisms obtained from a diesel storage facility were used as inoculum. Biofilm growth and viability were quantified by a crystal violet assay and hydrolysis of fluorescein diacetate, respectively. Results show that although there is greater accumulation of biofilm material in pure biodiesel samples metabolic activity is higher in pure diesel ones. Microbial community structure and composition were studied by community level physiological profiling (CLPP) and 16s rDNA sequencing. Principal component analysis of CLPP revealed that both biodiesel concentration and polymer type affect the structure and metabolic capabilities of biofilm communities. These results were confirmed by comparison of libraries of 16s rDNA for different polymers growing at different biodiesel concentrations. Genera isolated in the biofilm were characterized either by their ability to degrade hydrocarbons, produce surfactants or degrade polyethylene or polyamide-11. The results of this study may lead to a better understanding of microbial effects on storage materials for diesel/biodiesel blends.