Screening Of Strains Producing ?-Poly Glutamic Acid And Research On Fertilizer Efficiency

Poly-gamma-glutamic acid(?-PGA)is new biopolymer,composed of glutamic acid monomers,which are dehydrated by gamma-amide bond.In view of excellent capacity,such as good hydrophilic,strong water absorption,degradability and biocompatibility,gamma-pga has broad application prospects in many fields such as agriculture,food,medicine,cosmetics and sewage treatment.In agriculture,?-PGA is often used as a fertilizer addition agent and water retention agent.Aimed at screening a strain producing ?-PGA from soil and fermented soya beans,the research was focus on the synergy between fertilizer retention function of ?-PGA and growth promoting function of Bacillus subtilis,and its effects on growth and yield of the pepper.From bacterial colony morphology,microscopic examination results and sequence analysis of 16 S rDNA,it was concluded that the strains screened from soil belonged to Bacillus subtilis.The thin layer chromatography results of the hydrolysate of the fermentation product showed that glutamic acid was the only hydrolysate,proved that the fermentation product was poly glutamic acid.The viscous molecular weight of poly glutamic acid is 1088 kDa.The fermentation conditions,optimized by single factor experiment,were as followed: The bean dregs was the best solid substrate fermentation among three kind of solid matrices including alcohol,soybean residue and corn meal;the optimal water content of the solid medium and the optimal initial pH were 60% and 7.5 respectively.With fermentation products of WJ47 strain used as bacterial fertilizer,four different treatments with soil were carried out to study the effect of bacterial fertilizer on growth and yield of pepper.The results showed that the growth of pepper was promoted,and the yield of pepper was significantly increased,by about 30.4%.During this period,the number of bacteria in WJ47 strain in soil was detected by coating counting to reflect the growth of WJ47 strain in soil.The results showed that the strain of WJ47 could survive in long term.Saline-alkali stress experiments were conducted to investigate the resistance of the strain WJ47 to adverse physical and chemical environment by using different concentrations of NaCl(0~5%)and different pH(7-10).The results showed that the strain of WJ47 possessed high resistant,and could thrive in NaCl solution of high salt(5%NaCl)or in alkaline environment with a pH of no bigger than 9.0.