Recovery Of Glutamic Acid With Zero Pollution

This paper studied the glutamic acid extraction in the isoelectric point mother solution. Firstly, bacteria removal in the glutamic acid isoelectric point mother solution was studied. Polyacrylate sodium was used as the flocculation agent. The experimental results showed that the optimum conditions were as follows: polyacrylate sodium 2%, pH 3.6, temperature 60℃, stirring speed 20r/min and stirring time 15min.The removal rate of the bacteria was above 90%. Then, glutamic acid thalli was treated with diluted acid and hydrolyzed by protease to obtain amino acid hydrolysate. The optimal hydrolytic conditions were determined by orthogonal test: the protease amount ,400U/g; temperature, 40℃; pH ,7.5; hydrolytic time, 12 hours; and substrate concentration ,1:30. The protein hydrolysis yield was 72.4% under these conditions. The optimum desalination process was determined, and the second isoelectric point crystallization. was also studied. The extraction yield of glutamic acid was above 70%. The solubility and supersolubility curves for glutamic acid crystallization in pure water, solutions containing 0.1% bacteria, and 1% NH4+, and practical industrial fermentation broth were measured experimentally. By fitting these curves mathematically, the widths of the metastable zones for glutamic acid in these four systems were calculated. The experimental results showed that the widths of the metastable zones decreased gradually in the systems of pure water, solutions of 0.1% bacteria, and 1% NH4+, and practical industrial fermentation broth, which means the solubility in these systems increases in the same sequences. The solubility and supersolubility curves had the following common mathematical formula:.The metastable zone widths of glutamic acid solution at different cooling, agitation, and crystallization growth rates, as well as the induction periods of crystallization nucleation under different supersaturations were measured. The experimental results showed that glutamic acid solubility increases moderately with the increase of temperature, the metastable zone width increases with the increase of the cooling rate and decreases with the increase of agitating rate. The crystallization growth rate of glutamic acid increases and the induction period decreases with the increase of supersaturation.