본 연구에서는 미세조류의 광합성능력을 이용하여 이산화탄소를 고정화하고자 할 때 문제점의 하나로 여겨지고 있는 고농도 이산화탄소에 대한 저해현상을 구체적으로 살펴보고자 하였다. 특히 이산화탄소의 전달계수를 구하여 미세조류가 성장하고 있는 동안 배지 내에서 용존 이산화탄소 농도의 변화를 정량적으로 이해하고자 하였으며, 용존 이산화탄소의 농도에 따른 고정화속도의 변화를 수식적으로 표현하였다. 먼저 공급되는 기체 중의 이산화탄소 부분압이 0.035%(v/v)일경우 조류의 성장은 이산화탄소의 전달에 의하여 제한되었으며, 2%(v/v)이상에서는 제한현상은 극복될 수 있었고 용존 이산화탄소는 평형농도 부근에서 유지되었다. 그러나 혼합기체의 이산화탄소 부분압이 10%(v/v) 이상일 경우에는 용존 이산화탄소에 의하여 저해현상이 발견되었다. 이러한 저해현상을 정량적으로 기술하기 위하여 고정화속도를 용존 이산화탄소의 함수로 하는 경헙식을 도입하였으며 이는 광생물반응기의 운전조건에 독립적인 것으로 폭넓은 활용이 가능할 것이다. 또한 고농도 이산화탄소에 의한 저해현상은 가역적임을 실험적으로 입증하였으며 이는 생물학적 이산화탄소 고정화 공정이 단기적인 고농도 이산화탄소에 의한 총격에 유연함을 보여주고 있다. 따라서 본 연구의 결과는 이산화탄소의 전달현상 및 농도에 따른 활성저해 현상을 이해하고 이를 수학적으로 기술함으로써 향후 광생물반응을 모델링하고 운전변수를 최적화하는데 기여할 수 있을 것으로 판단된다.

Batch cultivation of Chlorella vulgaris was carried out under various CO₂ concentrations in order to understand and describe mathmatically the CO₂ inhibition of microalgal CO₂ fixation. The volumetric CO2 transfer coefficient from mixture gas to culture medium was estimated from the volumetric O₂ transfer coefficient obtained experimentally. Using this transfer coefficient and aquatic equilibrium relationship between dissolved inorganic carbons, the behavior of dissolved CO₂ was calculated during microalgal culture. When air containing 0.035%(v/v) CO₂ was supplied into microalgal culture, the fixation rate was limited by CO₂ transfer rate. However, the limitation was disppeared by supplying mixture gas containing above 2%(v/v) CO₂ and the dissolved CO₂ concentration was maintained at the saturated value. In the range of CO₂ partial pressure in the flue gases from thermal power stations and steel-making plants, the microalgal CO₂ fixation rate was inhibited. The CO₂ fixation rate was succesfully formulated by a new empirical equation as a function of dissolved CO₂ concentration, which could be useful for modeling and simulating performance of photobioreaction with enriched CO₂. Also, it was found that the CO₂ inhibition of microalgal CO₂ fixation was reversible and that microalgal CO₂ fixation process could be stable against a shock of unusually high CO₂ concentration.

Biological Carbon Dioxode Fixation Carbon Dioxide Concentration Microalgal Culture Carbon Dioxide Transfer Rate Microalgal Growth Kinetics

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