Abstract
For the maximum production of pullulan from glucose as a carbon source, the effects of glucose concentration, pH and dissolved oxygen concentration on the cell growth and mass production of high-molecular weight pullulan by A. pullulans ATCC 42023 were evaluated. A. pullulans showed optimum pullulan productivity when glucose concentration was 0.3M (54g/L). And inhibitory effects on the cell growth and the pullulan production were observed at the glucose concentration higher than 0.3M (54g/L). The influence of pH control and dissolved oxygen on the pullulan production and growth of A. pullulans was studied. In shake-flasks, maximum pullulan production was obtained with $11.98g/{\ell}$ when initial pH was 6.5. In the batch fermentation, the maximum pullulan production of $13.31g/{\ell}$ was obtained with constant pH 4.5. And it was found that pullulan yield and synthesis rate increased with oxygen availability. For the production of commercially useful pullulan with high-molecular weight, a mixed carbon source, which was a mixture of glucose and glucosamine, was used for the pullulan fermentation with A. pullulans. On the basis of 5% mixed carbon source, culture with 3% glucosamine with 2% glucose was optimum condition for the production of high (M.W.> 1,000,000) and medium (M.W.> 200,000) molecular weight pullulan with considerable yields of cell mass and product. And the influence of pH control on the molecular weight of pullulan was studied in batch fermentation. It was found that the productivity of high-molecular weight pullulan with pH control at 6.5 was higher than that with no pH control.
A. pullulan ATCC 42023를 사용하여 고분자량의 pullulan을 대량생산하기 위한 연구로써, 탄소원의 농도, 용존산소량과 pH가 균체 성장 및 pullulan 생산에 미치는 영향에 대하여 연구하였다. Glucose의 당 농도에 따른 실험결과에서 glucose 농도가 0.3M (54g/1)일 때 최대의 pullulan 생산률을 나타내었고, 0.3M (54g/1)이상에서는 productivity가 급격하게 감소하는 기질 저해현상을 나타내었다. 삼각플라스크를 이용한 초기 pH의 영향에 대한 실험결과, 초기 pH 6.5는 $11.98g/{\ell}$의 pullulan을 생산하였고, pH 4.5로 일정하게 조절한 결과, pullulan 생산은 $13.31g/{\ell}$의 최대값을 나타내었다. 그러나 균체성장은 pH 6.5에서 가장 높았다. 그리고 용존산소량의 증가로 pullulan productivity를 증가시킬 수 있었다. 또한 산업적으로 유용한 고분자량의 pullulan을 생산하기 위한 탄소원으로 아미노당인 glucosamine을 사용하여 pullulan의 생성 및 분자구조 변형에 대하여 실험하였다. 탄소원 농도 50g/1 기준에서, glucose와 glucosamine을 40 : 60의 비율로 혼합하여 공급 하였을 때 분자량 20만 이상의 mediun size 및 200만 이상의 high molecular weight의 productivity가 가장 높았으며, A. pullulans의 specific growth rate도 가장 높았다.
