Effect of Ammonium Ion on the Production of a Polysaccharide, Methylan from Methanol by Mentylobacterium organophilum

Methylobacterium organophilum에 의한 메탄올로부터 메틸란의 생산에 대한 암모니아 이온의 영향

The effect of nitrogen source on production of a high viscosity exopolysaccharide, methylan, from methanol by Mentylobacterium organophilum was investigated in fed-batch culture. During the fermentation, cells continued to grow even after the nitrogen source added to the medium was depleted and methylan production was stimulated under the condition which ammonium ion was depleted. Cell growth increased proportionally to the initial concentration of ammonium ion in the medium, but methylan production was significantly inhibited at the high concentration of ammonium ion. As the initial concentration of ammonium ion increased, the specific growth rate, the specific product formation rate and the specific substrate consumption rate decreased due to the inhibitory effect of excess ammonium ions. In order to reduce the inhibitory effect by high concentration of ammonium ion. The control of ammonium ion concentration within the desired level(usually $0.45g/\ell$) was necessary. When ammonium ion concentration was maintained below $0.15g/\ell$ by exponential feeding, methylan production could be increased up to $12.5g/\ell$.

Methylobacterium organophilum을 이용하여 메탄 올로부터 고점성 다당류의 생산에 대한 질소원 이용의 통력학척 분석을 유가식 배양에서 수행하였다. 발효중 세포는 배지 중에 첨가된 질소원이 고갈된 후에도 계속 성장하였고, 에틸란은 질소원 고갈조건 하에서만 생성되였다 세포 성장은 배양초기에 첨가 한 질소원인 암모니아의 농도에 비례적으로 이루어 졌으나, 에릴란 생산은 첨가한 암모니아 농도가 $0.75g/\ell$ 이상에서는 오히려 현저하게 감소하였다. 초기 암모니아 농도가 높아질수록, 비세포중식 속도, 비산물생성 속도, 비기질소비 속도가 감소하였다. 높 은 암모니아 농도의 발효 속도들에 대한 저해작용을 감소시키기 위해, 질소원을 일정농도(암모니아 농도=$0.15g/\ell$) 이하로 유지시키면서 공급하는 유가식 배양법으로 메틸란의 농도를 $12.5g/\ell$ 까지 증가시킬 수있었다.