상세정보

고부가가치 물질을 함유하는 미세조류 바이오매스 대량생산을 위하여 경제적인 비닐소재로 만들어진 thin-film photobioreactor (TF-PBR)은 바이오파울링 현상을 유발하고 광투과율을 약화시킨다. 바이오필름의 형성은 바이오매스의 생산성을 떨어뜨리며 오염가능성을 증가시켜 생산된 바이오매스의 순도에 영향을 줄 수 있다. 계면화학적 관점에서 바이오파울링 현상을 심부 배양 시 발생하는 기포에 의한 물리적인 부착과 고농도 세포배양 시 사멸하는 세포에 의해 생성되는 거품에 의한 화학적인 부착 두 가지의 복합적인 원인으로 인하여 발생됨을 규명하고자 하였다. 각 조건은 모사된 바이오필름의 생성조건에 의해 정량적으로 측정되었다. 또한, 생성된 바이오필름의 패턴을 분석하여 물리적인 부착에 따른 바이오필름의 감소에 최적인 부유 구조체의 형상을 결정하였고, 구 형태의 10 mm 부유 구조물에 대하여 최적화가 완료되었다.
Buoyant ball을 사용한 결과, TF-PBR의 headspace 부분의 바이오필름이 현저히 감소한 것을 수치적으로 확인하였으며, Neochloris oleoabundans의 바이오매스 생산성이 6일차에 이르러 32.03%까지 향상되었다. 본 기술은 심부배양으로 이루어지는 다양한 균주에 대하여 범용적으로 적용이 가능하며 오염방지 및 반응기의 재사용을 용이하게 한다.


In the mass cultivation of microalgae for producing biomass containing high value-added substances, the thin-film photobioreactor (TF-PBR) made of a polymer film causes biofouling and attenuates the light transmittance. The formation of biofilm impairs biomass productivity and increases the potential for contamination, which poses a challenge to the purity of biomass. In the aspect of surface chemistry, it is examined that biofouling occurs due to two main factors: physical adhesion by aeration and chemical adhesion by foam generated by cells that die. In each condition, the biofilm is quantitatively measured by simulated conditions. By analyzing the pattern of the generated biofilm, the optimal shape and size of the buoyancy structure of the biofilm were determined according to the physical adhesion. Optimization of the shape and size of the structure was completed with a 10 mm buoyant sphere ball. As a result of using the buoyant ball, it was numerically confirmed that the biofilm of the headspace of TF-PBR was significantly reduced. Additionally, the biomass productivity of Neochloris oleoabundans was improved to 32.03% on day 6. This strategy can be applied universally in various strains under outdoor large-scale cultivation through reactor reuse and contamination prevention.

Contents	i
Abstract	iii 
List of Figures	vi
1. Introduction	1
2. Research Background	6
 2.1. Production of valuable products from microalgae	6
 2.2. Scale-up and mass cultivation of microalgae	7
 2.3. Prior research of anti-biofouling technology	9
 2.4. Microalgae biofilm formation	12
 2.5. Mechanism of antifoaming agent on the medium surface	13
3. Materials and Methods	15
 3.1. Algal stain and culture cultivation	15
 3.2. Definition of infection rate	18
 3.3. Manufacturing of buoyant structure	19
 3.4. Mass cultivation of polymer film photobioreactor	21
 3.5. Mass cultivation of semi-continuous process	22
 3.6. Analytical methods for biomass	23
 3.7. Quantification of microalgae biofouling by imageJ (NIH)	25
 3.8. Buoyant structure reuse and washing test	26
4. Results and Discussion	27
 4.1. Biofouling and cell loss by wall growth	27
 4.2. Wall growth pattern for antifoaming agent	32
 4.3. Determination of buoyant structure shape	39
 4.4. Effect of buoyant ball size on the biofilm pattern	44
 4.5. Buoyant ball washing and reuse	56
 4.6. Outdoor batch cultivation by LNG powerplant flue gas	61
5. Conclusion	66
References	67
Acknowledgments	75