Enhanced CO₂ Conversion in Chemoautotrophic Cultivation of Cupriavidus necator H16 Using a CO₂-Pulsed pH-Stat System with Intermittent Sodium Bicarbonate Feeding
- 발행기관 서강대학교 일반대학원
- 지도교수 나정걸
- 발행년도 2025
- 학위수여년월 2025. 8
- 학위명 석사
- 학과 및 전공 일반대학원 화공생명공학과
- 실제 URI http://www.dcollection.net/handler/sogang/000000081989
- UCI I804:11029-000000081989
- 본문언어 영어
- 저작권 서강대학교 논문은 저작권 보호를 받습니다.
초록 (요약문)
In the bioconversion of CO₂ using the chemoautotrophic microorganism Cupriavidus necator H16, conventional continuous CO₂ supply is limited by low carbon utilization efficiency, as the gas supply often exceeds the actual microbial demand. To address this issue, we developed a novel system that precisely controls CO₂ supply by linking it to the real-time metabolic activity of the microorganism. The system is based on a CO₂-pulsed pH-stat control, combined with a dynamic feeding strategy that employs sodium bicarbonate (NaHCO₃) as both an initial substrate and a stabilizing agent. The pH-stat system, which supplies CO₂ triggered by a pH increase resulting from its consumption, initially faced operational failure; the control loop ceased upon the depletion of dissolved inorganic carbon (DIC), which eliminated the pH signal. The introduction of NaHCO₃ resolved this issue by providing an initial DIC source to activate the pH-stat system. It simultaneously ensured system stability by serving as a carbon source buffer when CO₂ supply temporarily lagged demand. We first evaluated the effects of various static initial concentrations of NaHCO₃ (0.5–4 g/L), identifying a trade-off between productivity and efficiency. To overcome this, we ultimately designed and implemented an intelligent fed-batch control logic. This strategy starts with a low NaHCO₃ concentration (0.5 g/L) and intermittently supplies NaHCO₃ only when a signal of impending system stall—detected by real-time monitoring of the CO₂ supply off-time—is triggered. As a result, the optimized dynamic system achieved a carbon conversion efficiency of up to 76.3% without sacrificing final cell concentration, a 3.1-fold improvement over the continuous feed control group (24.6%). The dynamic optimization strategy presented in this study offers a practical solution for maximizing carbon substrate utilization in CO₂-based bioprocesses, with significant potential for future industrial applications.
more목차
Contents 6
1. Introduction 13
2. Material and Methods 16
2.1. Microorganism and seed culture condition 16
2.2. Bioreactor operation 17
2.3. Experimental design and control strategies 18
2.4. Core control system implementation 21
2.4.1. Hardware and software platform 21
2.4.2. CO₂-pulsed pH-stat control logic 21
2.5. Sample analytical methods 22
2.6. PHB analysis 23
2.7. Analysis of carbon conversion efficiency and rate 23
2.7.1. Total supplied carbon 24
2.7.2. Total carbon in final biomass 25
2.7.3. Calculation of efficiency and rate 26
3. Results 27
3.1. Limitations of the continuous CO₂ supply method (Control group analysis) 27
3.2. Development and rationale of the pH-Stat control strategy 28
3.3. Performance of the static CO₂ pulsed pH-stat System: Effect of initial NaHCO₃ concentration 30
3.4. Process optimization via a dynamic fed-batch CO₂-pulsed pH-stat system 33
4. Discussion 38
5. Conclusion 40
6. References 41
