Biopolymeric porous structure for selective oil sorption and activity intensification of oil-degrading bacteria

Abstract

Oil pollution is one of the environmental concerns that are currently becoming a major issue in the petroleum industry. Among the different methods for environmental cleaning, the use of sorbents to recover the spilled oils is becoming more and more attractive because of their peculiar advantages such as reusability and recoverability of the oil. In this context, bioremediation is often considered a promising and cost-effective technology that could help a more sustainable recovery of contaminated water by using oil-degrading microorganisms. In this work, it is proposed a PCL-based biodegradable and floatable oil removal sponge, able to immobilize and increase biodegradation ability of hydrocarbon-degrading bacteria for bioremediation purpose. The sponges were prepared by combining melt mixing and particulate leaching. In brief, PCL, PEG and NaCl were fed to a batch mixer and processed until a constant value of torque was achieved. The blends were then compression molded in a laboratory press in appropriate cylindrical molds. Finally, the porogen parts of the blends (NaCl and PEG) were removed by selective leaching in demineralized water. The sponge was used to immobilize performant hydrocarbon-degrading bacterial strains and tested for biodegradation efficiency on crude oil. The sponge morphology before and after the bacterial immobilization was investigated with scanning electron microscopy (SEM). The sponge morphology was characterized by a multimodal pore structure with distinct pore sizes ranging from 50 to 100 micrometers. SEM analysis confirmed the high capacity of colonization by bacterial cells within the 3D porous structure. The sponges showed an uptake efficiency up to 500 wt% and high reusability since retained almost 90% of their initial absorption capability up to 50 cycles. The device obtained using this floatable and degradable formulation hosting immobilized cells was able to degrade crude oil more efficiently than the conventional free-cell systems demonstrating to be adequate as carrier for bioremediation purposes.