Petroleum-degrading enzymes: screening and performance improvement by immobilization and surfactants

Abstract:

The oily sludge produced in petroleum exploitation and processing is the main pollution source in the petrochemical industry, causing continuous harm to the surrounding eco-environment. Bioremediation as an effective and sustainable technology has attracted much attention. However, the current studies focus on the microbial degradation of petroleum in oily sludge and rarely report enzymatic degradation. [Objective] This study aims to screen petroleum-degradation enzymes by computer simulation and experimental techniques and improve the degradation effect by adding surfactants and enzyme immobilization. [Methods] Molecular docking was employed to analyze the possibility and mode of binding of target enzymes to common substrates in petroleum and the strongest degrading enzyme was screened out by enzymatic degradation experiments. Furthermore, the degradation conditions of the enzyme screened out were optimized, and the degradation effect on petroleum was further improved by immobilization and addition of surfactants. [Results] A total of five petroleum-degrading enzymes were obtained by molecular docking simulation and experimental verification. Among them, Bacillus subtilis laccase (BsLac) exhibited the highest degradation rate of petroleum, which reached 34.1% at the time point of 72 h. Surfactants improved the degradation of BsLac on petroleum, and sophorolipid showcased the strongest promoting effect, with the highest degradation rate of 46.3% at the sophorolipid concentration of 1 000 mg/L. However, 2,2'-azinoo-bis(3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt (ABTS) did not present promoting effect on BsLac for petroleum degradation. The BsLac immobilized by peanut shell as the adsorption carrier exhibited the highest petroleum degradation rate (56.3%). [Conclusion] We screened out the strongest petroleum-degrading enzyme by molecular docking and experimental verification. Furthermore, the immobilization of BsLac can improve the degradation performance on petroleum. The findings lay an experimental and theoretical foundation for further exploring the enzymatic degradation of petroleum.