酵母细胞生物转化反式-肉桂酸生产L-苯丙氨酸的研究

INVESTIGATION OF THE BIOTRANSFORMATIONS OF TRANS-CINNAMIC ACID TO L-PHENYLALANINE BY USING YEAST CELLS

据文献调查,搜集了国内可能相关的30株酵母,进行生物转化反式-肉桂酸(t-Ca) 生产L-苯丙氨酸 (L-Phe) 的微生物筛选研究,并对部分菌株生物转化能力,即苯丙氨酸解氨酶 (PAL,EC _(4、3、1、5) 活性水平进行了初步评估。筛选结果是:22株酵母具有转化 t-Ca 生成 L-Phe 的能力,转化率在2—67％范围。选出7株酵母研究在液体培养条件下细胞生长和PAL活性的时间过程关系,PAL 活性范围在 2.3—14.4x10^(-s)u/m g细胞干重。深红酵母 (Rhodotorularubra) AS2.166作为生物转化制备实经菌株,在静止细胞和固定化细胞批式反应条件下,结果获得L-Phe分离产率分别为42.0％,28.7％。

Thirty strains of native yeasts, including two genera (Rhodotorula, Sporobolomyces), six species (R.glutinis, R.rubra, R.minita, R.sinesis, S.roseus, and S.salmonicolor) were screened for their ability to convorse trans-cinnamic acid(t-Ca) to L-phenylalanine(L-Phe) by using yeast cells. Primary evaluation of phenylalanine ammonia-lyase (PAL, EC 4.3, 1.5) activity from the selected strains was investigated. The results showed that twenty two strains were able to converse the substrate t-Ca, to the product, L-Phe at the level of concentrations of t-Ca,60mM, and NH_4OH, 6.5 M,in the media (pH=10.0) with conversions ranging from 2 to 67%. Seven organisms among them were studied on their cellgrowth and time course of the formation of PAL activity in an aqueous medium,and the PAL activities were from 2.3 to 14.4 × 10-3 U/mg cell dry weight. Preparative-scale production of L-Phe with one organism, Rhodotorula rubra (AS 2.166), including two types of biocatalysts, Resting Cells and Immobilized Cells, allowed for the isolation of L-Phe with 42.0 and 28.7 percent yields respectively.