反应条件下苯丙氨酸解氨酶的活力稳定性

Abstract

<正>在苯丙氨酸解氨酶(PAl)的作用下由肉桂酸和氨合成l-苯丙氨酸(l-PHE)是酶法合成该氨基酸的重要途径,国外已利用该途径进行l-苯丙氨酸的工业生产,但是该过程仍存在着转化率低和酶活力稳定性差的问题。为解决这些问题,有必要在现有基础上开展提高酶活力稳定性的研究。

By comparing the numbers of the consecutive reaction runs with a relative high PAL(phenylalanine ammonia-lyase)activity the stability of enzymic activity of PAL in the cells (R.glutinis NC06) was determined.Various methods except reducing the physical severity of the reaction conditions, such as high pH, high ammonia and trans-cinnamic acid concentrations, have been developed For stabilizing the PAL under the bio-conversion condition.The stability of the PAL in the cells can markedly be improved by omitting chloride ions (Cl-)From the reaction mixture and using anaerobic condition created by N2-sparking during the reaction process.The inclusion of glycerol,especially sor-bitol in the reaction mixture appeared to signiFicantly increase the stability of PAL in the cells.The substitution of (NH4)2CO3 or NH4Ac For NH3 in the reaction mixture and the immobilization of the PAL-containing cells by K-carrageenin also greatly contributed to the stability of the PAL activity.A combination of N2- sparking during the reaction process with inclusion of sorbitol and exclusion of Cl- in the reaction mixture increased the number of the consecutive reaction runs with a high PAL activity (more than 19.5 mg trans-cinnamic acid per g cell wet weight per hour) to 10-Fold that of the control which was carried out without any stabilizing means.