Lysine Production by Thialysine Resistant Mutant of Candida utilis ( I ) - Isolation of High Lysine Excreting Mutant of Candida utilis -

Candida utilis의 Thialysine 내성맥리주에 의한 Lysine생산 ( I ) -Candida utilis의 Lysine을 생산하는 Thialysine 내성맥리주의 분리-

Thialysine significantly inhibited the growth of wild type strain Gondida utilis NCYC-359. In the absence of thialysine, the culture reached stationary phase after 24hr, however, in the presence of 0.5% thialysine, the culture reached stationary phase after 40hr, respectively. Effect of amino acid or vitamin was investigated on recovery of the growth of wild type strain from thialysine inhibition. Glycine, methionine, arginine and tryptophan recovered growth inhibition by thialyslne to some extent. However, vitamins were inert. Especially, lysine at one eighth concentration of thialysine recovered almost fully the growth inhibition. Thialysine resistant mutants were induced from the parent strain of Condida utilis NCYC-359 by NTG treatment. Colonies of thialysine resistant mutants were obtained on agar minimal medium supplemented with 0.1-0.5% thialysine. The frequency of thialysine resistant mutants induced by the first mutation was the highest at 0.1% The wild strain produced no appreciable lysine extracellularly. However, almost thialysine resistant mutants excreted appreciably. Lysine excretion increased after repeated mutation. Finally, of the thialysine resistant mutants induced by NTG, Condida utilis TRN-4006 was obtained. This strain excreted lysine (400$\mu\textrm{g}$/$m\ell$) into the medium with a concomitant decrease of lysine in the intracellular pool.

Lysine의 analogue인 thialysine은 야생주 Candida utilis NCYC-359의 생육을 강력하게 저해했으며 0.1%에서는 18시간까지 9.5%에서는 24시간까지 본 효모의 유도기를 지연시켰다. thialyssine에 의한 야생주의 생육저해의 회복에 미치는 아미노산 및 비타민의 영향을 조사한 결과 glycine, mthionine, arginine, histidine 그리고 trypphan등은 어느정도 효과가 있었으며 비타민은 거의 효과가 없었다. 특히 최소배지에 L-lysine을 thialysine의 1/8량만 첨가해도 thialysine에 의한 생육저해는 거의 일어나지 많았다. NTC 1회 처리시 thialysine에 대한 내성을 나타내는 빈도를 보면 최소배지에 thialysine 0.1% 첨가시 그 빈도가 0.11%, 0.5%시 0.03%로 나타났으며 이 내성맥리주에 의한 lysine 생산능을 검토한 결과 최소배지에 첨가된 thialyslne의 농도와 lysine생산능과는 뚜렷한 관계가 성립되지 않았으며 NTC를 회복처리하여 균체외로 lysine을 다양 분필 하는(450$\mu\textrm{g}$/$m\ell$) thialysine 내성맥리주 Candida utilis TRN-4006을 최종적으로 분리선별하였다.