Molecular Profiling and Optimization Studies for Growth and PHB Production Conditions in Rhodobacter sphaeroides

Yu Rim Lee, Hana Nur Fitriana, Soo Youn Lee, Min-Sik Kim, Myounghoon Moon, Won-Heong Lee, Jin-Suk Lee and Sangmin Lee
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Yu Rim Lee: Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju 61003, Korea
Hana Nur Fitriana: Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju 61003, Korea
Soo Youn Lee: Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju 61003, Korea
Min-Sik Kim: Energy Resources Upcycling Research Laboratory, Korea Institute of Energy Research, Daejeon 34129, Korea
Myounghoon Moon: Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju 61003, Korea
Won-Heong Lee: Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, Korea
Jin-Suk Lee: Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju 61003, Korea
Sangmin Lee: Gwangju Bio/Energy R&D Center, Korea Institute of Energy Research, Gwangju 61003, Korea

Energies, 2020, vol. 13, issue 23, 1-14

Abstract: In the recent climate change regime, industrial demand for renewable materials to replace petroleum-derived polymers continues to rise. Of particular interest is polyhydroxybutyrate (PHB) as a substitute for polypropylene. Accumulating evidence indicates that PHB is highly produced as a carbon storage material in various microorganisms. The effects of growth conditions on PHB production have been widely studied in chemolithotrophs, particularly in Rhodobacter . However, the results on PHB production in Rhodobacter have been somewhat inconsistent due to different strains and experimental conditions, and it is currently unclear how diverse environmental factors are linked with PHB production. Here, we report optimized growth conditions for PHB production and show that the growth conditions are closely related to reactive oxygen species (ROS) regulation. PHB accumulates in cells up to approximately 50% at the highest level under dark-aerobic conditions as opposed to light aerobic/anaerobic conditions. According to the time-course, PHB contents increased at 48 h and then gradually decreased. When observing the effect of temperature and medium composition on PHB production, 30 °C and a carbon/nitrogen ratio of 9:1 or more were found to be most effective. Among PHB biosynthetic genes, PhaA and PhaB are highly correlated with PHB production, whereas PhaC and PhaZ showed little change in overall expression levels. We found that, while the amount of hydrogen peroxide in cells under dark conditions was relatively low compared to the light conditions, peroxidase activities and expression levels of antioxidant-related genes were high. These observations suggest optimal culture conditions for growth and PHB production and the importance of ROS-scavenging signaling with regard to PHB production.

Keywords: Rhodobacter; polyhydroxybutyrate; growth conditions; reactive oxygen species (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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