Kinetic analysis of photosynthetic growth and photohydrogen production of two strains of Rhodobacter Capsulatus

Abstract

Two mutants of Rhodobacter Capsulatus (JP91 and IR3), a photosynthetic purple non-sulfur bacterium, were grown in a batch photobioreactor under illumination with 30 mmol l −1 dl-lactate and 5 mmol l −1 l-glutamate as carbon and nitrogen source, respectively. Bacterial growth was measured by monitoring the increase in absorbance at 660 nm. The photosynthetic growth processes under different cultivated temperatures are well fitted by a specific logistic model to analyze the kinetics of photosynthetic growth of two strains, thus the apparent growth rates ( k) of these photosynthetic bacteria, the variations of cell dry weight (CDW) as well as their relationship with temperature are obtained. In present work, k is (0.1465 ± 0.0146), (0.2266 ± 0.0207) and (0.3963 ± 0.0257) h −1 for JP91 and (0.1117 ± 0.0122), (0.1218 ± 0.0133) and (0.2223 ± 0.0152) h −1 for IR3 at 26, 30 and 34 °C, respectively. And the difference between CDW max and CDW 0 is (0.8997 ± 0.0097), (0.8585 ± 0.0093) and (0.9241 ± 0.0099) g l −1 for JP91 and (0.8167 ± 0.0089), (0.7878 ± 0.0086) and (0.8358 ± 0.0091) g l −1 for IR3 at 26, 30 and 34 °C, respectively. Also real-time monitoring of hydrogen production rates is acquired by recording the flow rates of photohydrogen for these two strains under different temperatures. The effects of temperature on the bacteria growth, hydrogen production capability and substrate conversion efficiency are discussed based on these results. The most preferment temperature, 30 °C, showed good substrate conversion efficiency of 52.7 and 68.2% for JP91 and IR3, respectively.