Enhanced biodegradation of PAHs in historically contaminated soil by M. gilvum inoculated biochar

Abstract

The inoculation of rice straw biochar with PAH-degrading Mycobacterium gilvum (1.27 × 10 ± 1.24 × 10 cell g), and the subsequent amendment of this composite material to PAHs contaminated (677 mg kg) coke plant soil, was conducted in order to investigate if would enhance PAHs biodegradation in soils. The microbe-biochar composite showed superior degradation capacity for phenanthrene, fluoranthene and pyrene. Phenanthrene loss in the microbe-biochar composite, free cell alone and biochar alone treatments was, respectively, 62.6 ± 3.2%, 47.3 ± 4.1% and non-significant (P > 0.05); whereas for fluoranthene loss it was 52.1 ± 2.3%; non-significant (P > 0.05) and non-significant (P > 0.05); and for pyrene loss it was 62.1 ± 0.9%; 19.7 ± 6.5% and 13.5 ± 2.8%. It was hypothesized that the improved remediation was underpinned by i) biochar enhanced mass transfer of PAHs from the soil to the carbonaceous biochar "sink", and ii) the subsequent degradation of the PAHs by the immobilized M. gilvum. To test this mechanism, a surfactant (Brij 30; 20 mg g soil), was added to impede PAHs mass transfer to biochar and sorption. The surfactant increased solution phase PAH concentrations and significantly (P < 0.05) reduced PAH degradation in the biochar immobilized M. gilvum treatments; indicating the enhanced degradation occurred between the immobilized M. gilvum and biochar sorbed PAHs.

Bioremediation of crude oil‐contaminated soil by hydrocarbon‐degrading microorganisms immobilized on humic acid‐modified biofuel ash

“…Some carriers were also reported to improve the enzymatic activities of microbes, such as that of polyphenol oxidase and dehydrogenase, and transmission of oxygen into substrate . Agricultural wastes, such as peanut shell powder, sunflower seed husk, and biochar, as well as synthetic and natural polymers, have been used to produce MICs . Both biochar and activated carbon have good adsorption properties for petroleum contaminants and nutrients and exhibit optimal immobilization effects for microbes, but at a high cost.…”

“…[23][24][25][26][27] Agricultural wastes, such as peanut shell powder, sunflower seed husk, and biochar, as well as synthetic and natural polymers, have been used to produce MICs. [28][29][30] Both biochar and activated carbon have good adsorption properties for petroleum contaminants and nutrients and exhibit optimal immobilization effects for microbes, but at a high cost. Compared with biochar and activated carbon, raw agricultural wastes are inexpensive, although their immobilization effects for extraneous bacteria are usually not adequate.…”

Advanced Rhodococcus Biocatalysts for Environmental Biotechnologies

“…For example, the modified sawdust adsorbed up to 90% of heavy metal ions from contaminated water [76]. Furthermore, a diffusion distance between cells and a pollutant is shortened, and the (ad)sorbed pollutant molecules became readily biodegraded [77][78][79]. In contaminated soil, carriers act as bulking agents, facilitating aeration and moisture exchange, and therefore ensuring that microorganisms are sufficiently supplied with oxygen and water [78,80,81].…”

Advances in research on the use of biochar in soil for remediation: a review

“…pyrene, benzo(b)fluoranthene, and indeno (1,2,3-cd)) which depended on DOC for their transportation unlike pulverized biochar which depended on colloids formed after biochar addition. Recently, Xiong et al (2017) investigated the influence of a microbe-biochar composite (Mycobacterium gilvum and rice straw biochar) on the remediation of PAHs contaminated coke plant soil. The authors observed superior degradation of phenanthrene, fluoranthene and pyrene by 62.6, 52.1 and 62.1%, respectively after the treatment with microbe-biochar composite.…”