Study On L-Phenylalanine Bioconversion In Aqueous Two-phase System

L-Phenylalanine is a significant organic-chemical engineering intermediate, which is widely used in many fields such as food, medicine, and chemical engineering. It is a major feed additive to food, and an intermediate for anticancer medicament. For the more, it is a vital material to synthesize aspartames, which made it widely needed in the future market.Aqueous two-phase system is a new-style bioconversion system. Due to its many advantages, ATPS has been used in production of antibiotics, organic acids, and peptides. In this paper, ATPS was used as a reaction system, and the possibility of using ATPS in the way of synthesize L-phenylalanine catalyzed by enzyme was discussed. The influence of all the facts to extraction of the components used in the system was researched, and optimism compound was selected. The stability of enzyme embodied in E.coli during the reaction process was tested and the possibility of using ATPS as a reaction system was reviewed. In the end, the theory of ATPS composed by PEG/ phenylpyruvic acid sodium salt was researched.The extraction effects of different ATPS to substrate, bacteria, and product used in L-phenylalanine synthesize were also discussed. An ATPS composed by PEG 1000 (20%,w/w) /Na2HPO4 (16%,w/w) was selected as the reaction system, in which the partition coefficient for substrate phenylpyruvic acid was 5.56, for product L-phenylalanine was 1.06, and for bacteria was 11.2. In this system, the substrate and bio-catalyze material were mostly extracted to one phase while product was partly extracted to the other. The optimism condition was: pH at 8.5, temperature at 39C, concentration of salt NaCl at 20g/L, and concentration of surfactants at 0.02%.The catalyze ability of E.coli declined quickly in traditional aqueous system, while in ATPS, due to the protection to cells by PEG, bacteria could be used as bio-catalyze for many times. In single-batch conversion, the productivity in ATPS was just a little higher than in traditional aqueous system. While because muti-batch conversion in ATPS had the advantage of removing products during conversion,which could partly release product inhabitation, the productivity in it was improved 27.4% higher than in aqueous system.Beside ATPS composed by polymer/polymer, polymer/salt, a new type of ATPS composed by polymer/organic acid was discovered. It was found that PEG and the substrate solution of phenylpyruvic acid sodium salt in high concentration could directly form a type of ATPS, thus enlarged the field of ATPS theory. It was also proved that phenylpyruvic acid sodium salt and inorganic compound could both contribute forming of ATPS. Using phenylpyruvic acid sodium salt alone, the concentration must reach as high as 60g/L. By using a phenomenal that bacteria deposited after several times of conversion in muti-batch conversion, the deposit bacteria was removed and new bacteria was added, thus, the continues conversion could be realized.