The Key Pathways Of Organic Sulfur Removal By Thermophilic Bacterium Geobacillus Thermoglucosidasius W-2

Various forms of organic sulfur exist in crude oil.These organosulfur compounds can cause the emulsification of crude oil,lower oil quality,and emit large amounts of sulfur dioxide during combustion.Sulfur compounds in fossil fuels also bring about worldwide environmental problems.In order to reduce the environmental hazard of fuel combustion and meet increasingly strict emission standards,the sulfur content of fuel should be strictly cut down.Hydrodesulfurization?HDS?is widely used in the current method for organic sulfur removal.However,HDS treatment causes light products,the lower viscosity of gasoline and diesel,and thus is not suitable for the production of heavy marine fuel oil which needs much higher viscosity.Biodesulfurization?BDS?is a promising method to desulfurize sulfur-containing compounds in oil with its unique advantages,such as environment friendly treatments and moderate reaction conditions.To date,the reported bacteria involved in desulfurization are becoming increasingly,but most of them are mesophilic bacteria.Research on thermophiles is still lacking.In this study,thermophilic bacterium Geobacillus thermoglucosidasius W-2 is a strain of high-efficiency organic sulfur removal.The desulfurization rates of two initial total sulfur contents of 2.81%?high sulfur?and 0.46%?low sulfur?are close to40%and 55%,respectively.In order to study the key pathways and genes responsible for the removal of organic sulfur from the genetic level,common patterns of sulfur compounds in the crude oil dibenzothiophene?DBT?and benzothiophene?BT?were used as inducers to cultivate W-2.Transcriptome analysis indicated that some transporter genes and several key desulfurization genes?SsuD₁/SsuE₁ and SsuD₂/SsuE₂?were found to be significantly up-regulated in response to DBT induction.These desulfurization-related genes were considered to conduct key step to convert organic sulfur to inorganic sulfur.Functional characterization of the thermophilic alkanesulfonate monooxygenase systems SsuD₁/SsuE₁ and SsuD₂/SsuE₂showed that SsuD₁/SsuE₁ and SsuD₂/SsuE₂ exhibited considerable thermal and pH stability and wide organic sulfur substrates applicability.The presence of two sets of organic sulfur bioremoval systems may endow strain W-2 better viability and higher organic sulfur removal capacity.Taken together,the organic sulfur removal of heavy oil from G.thermoglucosidasius W-2 was studied systematically in this paper.Two sets of organic sulfur biological removal systems SsuD₁/SsuE₁ and SsuD₂/SsuE₂ were obtained.Further enzymatic characterization revealed that SsuD₁/SsuE₁ and SsuD₂/SsuE₂ had a good tolerance.This special sulfur metabolism not only provides the possibility for industrial applications,but also enhances the perception of the role of microorganisms in the natural sulfur cycle.