An enzymatic method using L-phenylalanine ammonia-lyase (EC 4.3.1.5) for the rapid conversion of trans-cinnamic acid to L-phenylalanine has been investigated. With Rhodotorula glutinis, enzyme activity as high as 0.3 U/ml of culture broth was obtained. The enzyme activity was kept stable for a relatively long time during cultivation by the addition of L-isoleucine. Optimization of the parameters of the conversion reaction resulted in accumulation of 18 mg of Lphenylalanine per ml of reaction mixture. The conversion yield from transcinnamic acid was about 70%. The method may provide a rapid and practical way to produce L-phenylalanine useful as an essential amino acid. L-Phenylalaninle ammonia-lyase (PAL; EC 4.3.1.5), an enzyme found in a variety of plants,
Enzymatic production of dihydroxyacetone (DHA) was studied by immobilization of the whole cells of acetic acid bacteria capable of oxidizing glycerol to DHA. Acetobacter xylinum A-9 cells immobilized in a polyacrylamide gel were selected as the most favorable enzyme preparation. The enzymatic properties of immobilized cells converting glycerol to DHA were investigated and compared with those of intact cells. The optimum pH for the immobilized cells was broad (4.0 to 5.5), whereas the intact cells had a narrow pH optimum at 5.5. The thermal stability of the immobilized cells was somewhat higher than that of the intact cells. Apparent Km values for glycerol with both intact and immobilized cells were about equal, 6.3 x 10-2 to 6.5 x 10-2 M. The complete conversion of glycerol to DHA was achieved within 40 h under optimum conditions, and pure crystalline DHA was readily isolated from the reaction mixture with over 80% yield.
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