Abstract
Bioaugmentation is a bioremediation option based on increasing the natural in-situ microbial population that possesses the ability to degrade the contaminating pollutant. In this study, a diesel-degrading consortium was obtained from an oil-contaminated soil. The diesel-degrading consortium was grown on wood waste that was plasma-pretreated. This plasma treatment led to an increase of bacterial attachment and diesel degradation rates. On the 7th day the biofilm viability on the plasma-treated wood waste reached 0.53 ± 0.02 OD 540 nm, compared to the non-treated wood waste which was only 0.34 ± 0.02. Biofilm attached to plasma-treated and untreated wood waste which was inoculated into artificially diesel-contaminated soil (0.15% g/g) achieved a degradation rate of 9.3 mg day−1 and 7.8 mg day−1, respectively. While, in the soil that was inoculated with planktonic bacteria, degradation was only 5.7 mg day−1. Exposing the soil sample to high temperature (50 °C) or to different soil acidity did not influence the degradation rate of the biofilm attached to the plasma-treated wood waste. The two most abundant bacterial distributions at the family level were Xanthomonadaceae and Sphingomonadaceae. To our knowledge, this is the first study that showed the advantages of biofilm attached to plasma-pretreated wood waste for diesel biodegradation in soil.
Highlights
The motivation for our study was an oil-spill disaster that occurred in December 2014, next to the Evrona Nature Reserve in southern Israel
Wood waste that was exposed to plasma led to a 3.5-fold increase in biofilm viability of the exogenously added P. putida F1 in MM supplied with toluene, and a 1.6-fold increase in MM supplied with glucose, compared to the untreated wood waste
The biofilms of P. putida and B. cereus grown on wood waste pretreated with plasma led to an increase of toluene degradation, compared to biofilms grown on untreated wood waste [24]
Summary
The motivation for our study was an oil-spill disaster that occurred in December 2014, next to the Evrona Nature Reserve in southern Israel. An oil pipeline a few kilometers away was breached, releasing 5000 m3 of crude oil into the reserve. An older spill was found 3 km further south, traced back to 1975 and holded 8000–10,000 cubic meters of contamination; for unknown reasons it had been ignored. About a third of the 1975 spill is estimated to still be present, enriching the soil with oil-degrading microorganisms. Oil contamination can be naturally biodegraded with indigenous oil-degrading bacteria. Enrichment of those in-situ bacteria with exogenous oil-degrading bacteria may be a key factor for increasing bioremediation rates
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