Isolated A Halophilic Strain With PHB-Accumulating Ability And Researched Its Product Characteristics

Polyhydroxyalkanoates(PHA)are polyesters produced by various bacteria under nutrient-limited conditions store carbon and energy.They have similar properties as the chemical plastics synthesized by the traditional fossil energy.PHA is a biodegradable and biocompatible,therefore it is very known as biological plastic polymers and has been widely utilized in pharmaceutical industry.Additionally,series compounds of PHA also have applications in material field due to their physicochemical characterization such as piezoelectricity and conductivity.In recent years,in order to improve the yield of PHA and decrease the production cost through biological methods are intensively studied in biological plastics industry.By cultivating halophilic microorganism can not only obtain high yield through pure bacteria fermentation,but also avoid sterilization process to achieve open cultivations because of its tolerance to hyperosmosis.In this study,the high yield PHA bacteria was isolated and identified from the soil samples of saline-alkali,the fermentation conditions were optimized as well.The characters types of PHA synthesized by Halomonas DQ-4 were analyzed by GC-MS,H-MMR,FT-IR etc.Strain samples were screened from saline soil from Daqing oilfield.A strain with high PHA yield named DQ-4 was isolated from outstanding six strains which were capable of synthesizing high yieldPHA through Sudan Black B and Nile Blue staining methods.DQ-4 was gram-negative bacteria and rod shaped.According to microbial morphology,16S rRNA sequence analysis,physiological and biochemical characteristics,DQ-4 was identified as Halomonas.The 16S rRNA sequence was uploaded to GenBank and login number was obtained as KT961118.A preliminary study about how nutrition and culture conditionsaffect synthesizing PHA of strain DQ-4 was done.In addition,the growth regulation of DQ-4 was studied as well.DQ-4 can use glucose,starch,glycerin,sodium acetate and other carbon resource to synthesis PHA.It reached maximum production yield while grown on glucose and carbon nitrogen kept a molar ratio of 100:7.The optimal broth content was 100 ml medium in 500 ml flask and the optimal growth condition was 38?,pH 9.0 at the shaking speed of 160 r/min.Consequently,the yield of PHA reached 5.88 g/L after 60 h cultivation and PHA occupied 71.3%of dry weight of the strain.PHA polymers synthesized within strains were extracted by sodium hypochlorite chloroform combing method.GC-MS analysis indicated the compounds accumulated in cells were PHB.The shift of corresponding monomer was determined by NMR,the results showed that the monomer molecular structure was consistent with the structure of PHB monomer.The IR maps of PHB standard sample and the polymers synthesized by strain DQ-4were similar since both of them had absorption peaks at 1726,2980,2934 and 2876cm"1.Therefore,the compounds synthesized by DQ-4 belonged to PHB.The TGA analysis result showed the initial degrade temperature was 198.6? and the maximum weight loss was about 90.66%,at 222.5?,which exhibited its good thermodynamic ability.Innatural degradation simulation test,PHB displayed the maximum degradation rate after 30 days and reached 45.82%after 60 days,which showedits good biodegradability.Preliminary experiments results show that the halophilic bacteria has the advantage of being the platform of synthesizing PHB compounds in low operation cost.This work provides a solid foundation to further researches about synthesizing PHB in open conditions,using cheap renewable organic waste as carbon source for the synthesis of PHB and improving conversion efficiency by genetic approaches.It also provides necessary theoretical basis for future large-scale industrial applications.