The Transformation Of Trans-Cinnamic Acid Into L-Phenylalanine By Rhodotorula Glutinis

L-Phenylalanine (L-Phe), an essential aromatic amino acid, had found wide use in food processing, feed additive and pharmaceutical industry. Aspartame, an important sweetener produced from L-phenylalanine was sanctified to sell by many countries whose wide application greatly increased the demand of L-phenylalanine.Properties of yeast were tested in synthetic medium by a serial of experiments, during which the enzyme-producing mode was determined, finding that phenylalanine ammonia lyase (PAL) was a kind of enzyme produced in the lag-phase. Based upon this kind of lag-phase-producing-mode model, PAL-producing dynamics was studied and the non-structure mathematic model was set up. The equation of this PAL-producing mathematic dynamics model listed herewith:The easier approach to work out the parameter and the significance of P were discussed. Factors, such as the inducer adding time, the amount of inducer, were analyzed. In Yamada medium, a kind of synthetic medium used in this paper in which Rhodotorula glutinis was cultured and PAL was induced, 0.40g/L L-Tyr, the inducer, was added in lag-phase.Experiments heretofore had set up the theoretical basis for optimizing PAL-producing conditions. Based upon the PAL-producing dynamic equation, experiments about optimizing PAL-producing conditions were performed. Yeast was transferred when the budding rate of Rhodotorula glutinis came up to the largest amount in the 18th hour in seed medium considering the culture's highest enzymatic activity in complex inducing medium. By single-factor experiments and orthogonal experiments, complex inducing medium was optimized (g/L) as follow: glucose 0.4, yeast extract 8.0, corn steep liquor 30.0, NaCl 5, KH2PO4 1.Salts, including MgSO4 '7H2O, FeSO4 '7H2O, MnSO4 -6H2O had little effects on the growth of Rhodotorula glutinis in complex inducing medium. 1.0g/L.K2HPO4 had better effect on the growth of Rhodotorula glutinis than 1.0g/L.KH2PO4 did.D-phenylalanine had the gratuitous effect on the inducing of PAL. After yeast was cultured in complex inducing medium for 8h, 0.40g/L L-Tyr and 0. lOg/L DL-Phe were added to complex inducing medium. By optimizing the PAL-producing condition, the non-growth-coupled specific PAL-producing rate was increased by 122 %, and the biomass was increased by 4.5%.In this paper, trans-cinnamic acid was conversed by resting yeast cell inconversion-solution. The conversion solution composition was optimized which was: 5.6mol/L [NH4+], 14.5% [HCO3~] . (The concentration of trans-cinnamic acid was 1.0% and pH was 10.5). Mycostatin had little or negative effect on PAL-producing. Cetylpyridinium chloride can increase the bioconversion rate.By single-factor experiments, the effects on the stability of PAL of sodium glutamate, sodium alginate, polyethylene glycol, glycerin, zinc powder, nitrogen gas were studied. By orthogonal experiment and divergence analysis, 1 .Og/L zinc powder and 20g/L sodium glutamate added to conversion-solution, the concentration of L-Phenylalanine was increased by from 18.7g/L to 27.52~31.90g/L, finding that those two effectors, zinc powder and sodium glutamate, had significant effects on the stability of PAL.