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y-aminobutyric acid (GABA), a four-carbon nonprotein amino acid, serves as a major inhibitory neurotransmitter in mammalian nervous systems, lying to lead 40% to restrain nerve conduction above, participating in the physiological activities of the brain circulation. GABA has several physiological functions such as hypotensive activity, treatment of epilepsy, tranquilizing and allaying excitement,enhancing memory, controlling asthma, regulating hormone secretion, promoting reproduction and activating liver and kidney function. Therefore it can be widely used in healthy foods and medicines as a new funchional factor.By using LP-GB 01-21 that can produce y-aminobutyric acid with highly efficient was screened in our laboratory. In this paper, we study on immobilized LP-GB 01-21 and separated y-aminobutyric acid from the whole-cell transforming solution. The maincontents of this work are as follows:(1) The immobilized LP-GB 01-21 embedded in sodium alginate, carrageenan and gelatin, to produce y-aminobutyric acid. By comparing the immobilized cells enzyme activity recovery and mechanical strength of the embeding materials, the sodium alginate was selected as a suitable carrier for immobilization. The research results showed that the optimal immobilization condition for y-aminobutyric acid production was as follows:sodium alginate concentration 2.0%, calcium chloride concentration 0.2 mol/L, cell density 80.0 g/L, and curing time 2 h, immobilized gelatin granule diameter 3.0 mm, mechanical strength 468.0 g/cm2. Under this condition, the enzyme activity recovery was 76.8%.(2) The substrate concentrations, reaction pH, temperature and the buffer concentrations were optimized as 50.0 g/L, pH 4.8,35℃and 0.1 mol/L, respectively. By comparing the immobilized cells and free cell, the results showed that thermal stability and pH tolerance of immobilized cells was significantly higher than free cells. Under the optimized reaction conditions, the recycled number of immobilized cells is also more than free cell, and the molar yield of y-aminobutyric acid by immobilized cells still reached more than 80% after ten times.(3) The separation process of y-aminobutyric acid from the whole-cell transforming solution. A simple and effective procedure, pretreatment transforming solution, decolorization, rotary evaporation and crystallization, was brought forward. The operating conditions of each step were discussed in detail. The recovery of y-aminobutyric acid in the whole process was about 89.4%, and the purity of the ultimate product could reach 96.7%, and pave the way for industrial production of y-aminobutyric acid.(4) The decolorizing technologcial conditions such as temperature, time, pH and amount of active carbon were mainly were studied. As a result, the optimum decolorization conditions were determined through single factor and orthogonal experiments as follows:activated carbon dosage 1.5%, decolorization temperature 70℃, pH value 4.0 and decolorization time 30 min. Under these conditions, the decolorization rate and recovery rate of bioconversion broth reached 98.4% and 97.2%, respectively.
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