Abstract
We investigated the biodesulfurization potential of a mixed culture AK6 enriched from petroleum hydrocarbons-polluted soil with dibenzothiophene (DBT) as a sulfur source. In addition to DBT, AK6 utilized the following compounds as sulfur sources: 4-methyldibenzothiophene (4-MDBT), benzothiophene (BT), and 4,6- dimethyldibenzothiophene (4,6-DM-DBT). None of these compounds supported the growth of AK6 as the sole carbon and sulfur source. AK6 could not grow on dibenzylsulfide (DBS) as a sulfur source. The AK6 community structure changed according to the provided sulfur source. The major DGGE bands represented members of the genera Sphingobacterium, Klebsiella, Pseudomonas, Stenotrophomonas, Arthrobacter, Mycobacterium, and Rhodococcus. Sphingobacterium sp. and Pseudomonas sp. were abundant across all cultures utilizing any of the tested thiophenic S-compounds. Mycobacterium/Rhodococcus spp. were restricted to the 4-MDBT culture. The 4-MDBT culture had the highest species richness and diversity. Biodesulfurization of DBT by resting cells of AK6 produced 2-hydroxybiphenyl (2-HBP) in addition to trace amounts of phenylacetate. AK6 transformed DBT to 2-hydroxybiphenyl with a specific activity of 9 ± 0.6 μM 2-HBP g dry cell weight−1 h−1. PCR confirmed the presence in the AK6 community of the sulfur-specific (4S) pathway genes dszB and dszC. Mixed cultures hold a better potential than axenic ones for the development of a biodesulfurization technology.
Highlights
The increasing global human population accompanied by extensive fossil energy consumption has posed serious threats to the environment and human health (Maass et al, 2015)
The biodesulfurization activity of the AK6 mixed culture was estimated as the amount of 2-HBP produced at different time intervals in resting cell assays with DBT as a substrate
A mixed bacterial culture AK6 was enriched from hydrocarbonspolluted soil based on its biodesulfurization competency
Summary
The increasing global human population accompanied by extensive fossil energy consumption has posed serious threats to the environment and human health (Maass et al, 2015). Governments and environmental organizations worldwide have recognized the problem and implemented strict regulations and legislations that limit the amount of sulfur in transportation fuels. The petroleum refineries are facing the problem that crude oil feeds are becoming heavier with high sulfur content, which means high sulfur levels in both straight-run and secondary processed diesel oil (Bhatia and Sharma, 2006). This will make the HDS process more economically and technically challenging, with the stringent environmental legislations that tend to limit sulfur content of transportation fuels to less than 10 ppm (Monot and Warzywoda, 2008)
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