Biodesulfurization of Dibenzothiophene and Its Derivatives Using Resting and Immobilized Cells of Sphingomonas subarctica T7b

Abstract

The desulfurization ability of Sphingomonas subarctica T7b was evaluated using resting and immobilized cells with dibenzothiophene (DBT), alkyl DBTs, and commercial light gas oil (LGO) as the substrates. The resting cells of S. subarctica T7b degraded 239.2 mg of the initial 250 mg of DBT/l (1.36 mM) within 24 h at 27 degrees C, while 127.5 mg of 2-hydroxybiphenyl (2-HBP)/l (0.75 mM) was formed, representing a 55% conversion of the DBT. The DBT desulfurization activity was significantly affected by the aqueous-to-oil phase ratio. In addition, the resting cells of S. subarctica T7b were able to desulfurize alkyl DBTs with long alkyl chains, although the desulfurization rate decreased with an increase in the total carbon number of the alkylated DBTs. LGO with a total sulfur content of 280 mg/l was desulfurized to 152 mg/l after 24 h of reaction. Cells immobilized by entrapment with polyvinyl alcohol (PVA) exhibited a high DBT desulfurization activity, including repeated use for more than 8 batch cycles without loss of biodesulfurization activity. The stability of the immobilized cells was better than that of the resting cells at different initial pHs, higher temperatures, and for DBT biodesulfurization in successive degradation cycles. The immobilized cells were also easily separated from the oil and water phases, giving this method great potential for oil biodesulfurization.

Biodesulfurization: a mini review about the immediate search for the future technology

“…These microorganisms show a higher capacity of desulfurization than previously described in the literature (Boniek et al 2010). In earlier studies, one Gram-negative species known as Sphingomonas subarctic was isolated in Japan, and it was proved that it possesses an efficient ability to desulfurizate DBT considering the industrial perspectives (Gunam et al 2006(Gunam et al , 2013.…”

Characterization of a MexAB-OprM efflux system necessary for productive metabolism of Pseudomonas azelaica HBP1 on 2-hydroxybiphenyl

“…Given the increased importance of biodesulfurization processes to clean up oil and coal (Alves and Paixao, 2011; Gunam et al, 2013), strains such as P. azelaica HBP1 should find increased usage to decontaminate the produced 2-HBP, before this is released in an untreated form and can do further environmental damage because of its toxicity.…”

“…As a consequence of its widespread use, 2-HBP can be found in persistent low quantities in sewage effluents (Yu et al, 2011). In addition, 2-HBP is the most important byproduct of biodesulfurization of oil and coals, formed through microbial conversion of dibenzothiophene (Gunam et al, 2013), causing both acute and chronic toxicity to the microbial strains in the conversion process (Alves and Paixao, 2011). As substituted phenol 2-HBP is a weak hydrophobic acid that can occur both in its protonated and dissociated form; the dissociated form being able to take up protons from the cytoplasmic interior across the membrane to the extracellular environment.…”

A Review on Desulfurization Techniques of Liquid Fuels

“…Gunam et al [34] applied gram bacteria (Sphingomonas subarctica T7b) for degradation of sulfur compounds (DBT, 4,6-dibutyl DBT and 4,6-Dipentyl BDT) from liquid fuels. They also studied the ability of Sphingomonas subarctica T7b by using of resting and immobilized cells with DBT, alkyl DBT and commercial light gas oil as the substrate.…”