Reconstruction of microbiome and functionality accelerated crude oil biodegradation of 2,4-DCP-oil-contaminated soil systems using composite microbial agent B-Cl.

Biodegradation is one of the safest and most economical methods for the elimination of toxic chlorophenols and crude oil from the environment. In this study, aerobic degradation of the aforementioned compounds by composite microbial agent B-Cl, which consisted of Bacillus B1 and B2 in a 3:2 ratio, was analyzed. The biodegradation mechanism of B-Cl was assessed based on whole genome sequencing, Fourier transform infrared spectroscopy and gas chromatographic analyses. B-Cl was most effective at reducing Cl- concentrations (65.17%) and crude oil biodegradation (59.18%) at 7 d, which was when the content of alkanes ≤ C30 showed the greatest decrease. Furthermore, adding B-Cl solution to soil significantly decreased the 2,4-DCP and oil content to below the detection limit and by 80.68%, respectively, and reconstructed of the soil microbial into a system containing more CPs-degrading (exaA, frmA, L-2-HAD, dehH, ALDH, catABE), aromatic compounds-degrading (pcaGH, catAE, benA-xylX, paaHF) and alkane- and fatty acid-degrading (alkB, atoB, fadANJ) microorganisms. Moreover, the presence of 2,4-DCP was the main hinder of the observed effects. This study demonstrates the importance of adding B-Cl solution to determine the interplay of CPs with microbes and accelerating oil degradation, which can be used for in-situ bioremediation of CPs and oil-contaminated soil.

A novel chitosan-biochar immobilized microorganism strategy to enhance bioremediation of crude oil in soil.

The chitosan-biochar composite is a clean and environmentally friendly immobilized microorganisms carrier. In this study, the chitosan-biochar composite as a carrier to immobilize a compound microbial agent contained Pseudomonas aeruginosa and Bacillus licheniformis, and investigated its role in the remediation of oil-contaminated soil. When using 1% (v/v) acetic acid, 3% (m/v) chitosan solution, 0.1% biochar, 4% (v/v) NaOH solution, freeze-drying 6 h, the optimal chitosan-biochar composite material could be obtained. The specific surfacearea of the material increased to 1.725 m2/g and the average pore size also increased from 130.2260 nm to 165.2980 nm after the addition of biochar through the analysis of specific surface area and pore size, which enlarged the contact area of microorganisms and crude oil with the material. SEM showed that the bacterial successfully adhered to the surface and internal of the material. Using FTIR, the results showed that the synthesis of composite carrier material was the covalent combination of -NH2 on chitosan and -COOH on biochar, forming a new chemical bond -NH-CO-. After 60 days of remediation of oil-contaminated soil, the removal rate of crude oil by chitosan-biochar composite immobilized microorganism method was 45.82%, which was 21.26% higher than that of natural remediation. Simultaneously, several oil-degrading bacteria increased at genus level, including Nocardioides (26.79%-33.09%), Bacillus (3.01%-4.10%), Dietzia (1.84%-5.56%), Pseudomonas (0-0.78%), among which Pseudomonas belongs to exogenous bacteria. The results indicated that the chitosan-biochar composite material has high application value in removing crude oil, and further provides a new strategy for bioremediation of oil-contaminated soil.