Construction And Desulfurization Characteristics Of Artificial Spores Of Desulfurization Bacteria

Dibenzothiophene（DBT）is the main organic sulfide in petroleum.Because it is difficult to dissolve in water,it is generally considered to be the most difficult sulfur-containing compound in petroleum to desulfurize and is difficult to remove with traditional desulfurization technology.As an important means to remove DBT from oil,biological desulfurization is usually limited by the difficulty of separating microorganisms after desulfurization treatment.Therefore,using functional microorganism for biological desulfurization of DBT has become a hot topic of research at home and abroad.In this study,an effectively DBT desulfurizing bacteria Gordonia sp.WQ-01A was purchased from the China Center of Industrial Culture Collection,and it was encapsulated by dopamine hydrochloride and Fe₃O₄ magnetic nanoparticles.Desulfurization ability and cyclic desulfurization effect of srtificial spores were explored in various degradation system,and determining that cell encapsulation has high application value in petroleum desulfurization.And the interaction between dopamine hydrochloride and magnetic nanoparticles with WQ-01A were explained from aspects such as Zeta potential,FTIR,VSM,and microstructure.Finally,the stress effects of ultraviolet light,high temperature（40℃）,low temperature（-20℃）and 75%ethanol and other external environments on desulfurization bacteria WQ-01A were explored.The specific research content and results are as follows:（1）A desulfurization bacterium Gordonia sp.WQ-01A,which uses DBT as the sole sulfur source,was purchased from China Center of Industrial Culture Collection.The study found that when the initial concentration of DBT was 0.25 mmo/L,there was no significant difference in degradation ability of artificial spores and native cell to DBT in an aqueous solution system.After96 h,the removal rate of DBT could reach more than 80%,and the formation of 2-HBP could also be detected during the degradation process.Moreover,the formation of 2-HBP in solution has a certain time lag compared to the degradation of DBT,so it can be inferred that WQ-01A desulfurization bacteria degrade DBT through the“4S”pathway.After culturing in the NAPL system for 48 h,it was found that the growth of artificial sopres lags behind that of native cell,and after 36 h,the degradarion amount of DBT of cell@PDA reached 0.25 mmol/L,while cell@PDA@Fe₃O₄,cell@PDA@Fe₃O₄@OA and native cell can completely degrade DBT after24 h.In addition,the recycling and reuse of artificial spores in the two degradation systema were also studied.The results showed that in the aqueous solution system,the recycling cycle of artificial spores and native cell was 96 h,and after 3 cycles of recycling,there was no significant difference in the degradation ability of DBT.In the NAPL system,the artificial spores had a cycle of 48 h,and after 3 cycles of recycling,the degradation ability of DBT of cell@PDA@Fe₃O₄@OA is similar to that of native cell,while the degradation ability of DBT of cell@PDA and cell@PDA@Fe₃O₄decereased after 3 cycles of recycling.（2）By measuring the contact angle of WQ-01A cells of desulfurization bacteria,it was found that the contact angle was 117.55°（reater than 90°）,which was hydrophobic bacteria.Cell@PDA and cell@PDA@Fe₃O₄ cells were measured,and it was found that their contact angles were less than 90°（73.05°and 48.52°,respectively）,which could form O/W type emulsions,with lower particle size,large EI value and poor emulsification performance.And the presence of bacteria is almost not observed at the oil-water interface,but a large number of bacteria can be found in the aqueous solution.However,the contact angle of cell@Fe₃O₄@OA is not much different from native cells,and both can form a stable picking emulsion,and the emulsion is W/O type.At the same time,a large number of bacteria can be observed at the oil-water interface.（3）Exploring the interaction between dopamine hydrochloride and magnetic nanoparticles and WQ-01A,it was found that the zeta potential of both artificial spores and native cell was negative,and the zeta potential of cell@PDA was lower.Secondly,strong FTIR bonds were observed around 580 cm^-1 and 634 cm^-1,which are the absorption vibrational peaks of Fe-O in Fe₃O₄.A strong peak at 1655 cm^-1 indicates the presence of C=O telescopic vibration.3297 cm^-1has a broad spectral peak,which is the vibrational absorption peak of N-H and O-H bonds in the dopamine hydrochloride molecule.The VSM curve of bacterial WQ-01A showed that compared to native cell and cell@PDA,magnetic nanoparticle cells exhibited significant superparamagnetization behavior,and cell@Fe₃O₄@OA have lower saturation magnetization intensity than cell@Fe₃O₄（17.7 emu/g and 47.4 emu/g）.The SEM structure of WQ-01A showed that native cell are short rod-shaped with smooth and independently distributed surfaces,cell@PDA surface folds of hydrochloride,and magnetic nanoparticle-encapsulated cells have rough surfaces and are covered with particulate matter.（4）By studying the stress effects of exteinal environments such as ultraviolet light,high temperature（40℃）,low temperature（-20℃）,and 75%ethanol on desulfurization bacteriun WQ-01A,it was found that desulfurization bacteria WQ-01A is more sensitive to ultraviolet light,and when directly exposed to ultraviolet light for 1 min,cell growth is significantly inhibited,with a survival rate of only 30%.However,after 2 min of ultraviolet light irradation,the survival rate of artificial spores can still reach more than 50%,even cell@PDA have a survival rate of up to 60%.Secondly,desulfurization bacteria WQ-01A is more tolerant to low temperature.After 10 min of low-temperature treatment,the survival rate of native cell and artificial spores can reach 60%,and the growth condition is good.However,after 10 min of high temperature treatment,the metabolic activity of native cell decreased,and the cell survival rate was less than 40%.However,after 30min of high-temperature treatment,the cell survival rate of artificial spore cells was still 50%.Finally,native cell and artificial spore were directly immersed in 75%ethanol solution,and it was found that after immersion for 3 min,both cells appeared to die,but the mortality rates of native cell were higher than those of artificial spores,which were 70%and 50%,respectively.