Role of Carbonyl Cyanide m-Chlorophenylhydrazone in Enhancing Photobiological Hydrogen Production by Marine Green Alga Platymonas subcordiformis

Abstract

We demonstrated that a significant volume of H(2) gas could be photobiologically produced by a marine green alga Platymonas subcordiformis when an uncoupler of photophosphorylation, carbonyl cyanide m-chlorophenylhydrazone (CCCP), was added after 32 h of anaerobic dark incubation, whereas a negligible volume of H(2) gas was produced without CCCP. The role of CCCP in enhancing photobiological H(2) production was delineated. CCCP as an ADRY agent (agent accelerating the deactivation reactions of water-splitting enzyme system Y) rapidly inhibited the photosystem II (PSII) activity of P. subcordiformis cells, resulting in a markedly decline in the coupled oxygen evolution. The mitochondrial oxidative respiration was only slightly inactivated by CCCP, which depleted O(2) in the light. As a result, anaerobiosis during the stage of photobiological H(2) evolution was established, preventing severe O(2) inactivation of the reversible hydrogenase in P. subcordiformis. The uncoupling effect of CCCP accelerates electron transfer from water due to a disruption of the proton motive force and release of DeltapH across the thylakoid membrane and thus enhances the accessibility of electron and H(+) to hydrogenase. The electrons for hydrogen photoevolution are mainly from the photolysis of water (90%). Upon the addition of CCCP, Chl a/b ratio increased, which implies a decrease in the light-harvesting PSII antennae or an increase in PSII/PSI ratio, possibly resulting in higher efficiency of utilization of light energy. The enhancement of H(2) evolution by the addition of CCCP is mostly due to the combination of the above three mechanisms. However, the disruption of the proton gradient across the thylakoid membrane may prevent a sustained photobiological H(2) evolution due to a shortfall of ATP generation essential for the maintenance and repair functions of the cells.

Effects of nutrient deprivation on biochemical compositions and photo-hydrogen production of Tetraselmis subcordiformis

“…Guan et al [5] in our laboratory made use of CCCP to increase the yield of hydrogen photoproduction by T. subcordiformis. Studies on the metabolic effects of CCCP indicate that [6,7] CCCP as an ADRY agent (agent accelerating the deactivation reactions of watersplitting enzyme system Y) rapidly inhibited the photosystem II (PSII) efficiency of T. subcordiformis cells. This resulted in a large decline in the oxygen evolution.…”

Purification and characterization of a hydrogenase from the marine green alga Tetraselmis subcordiformis

“…The alga was grown in sand-filtered natural seawater medium supplemented with micronutrients as described by Ran et al [12]. The pH was adjusted to 8.2 prior to autoclaving.…”

“…Regulation in T. subcordiformis was found to be different to that of C. reinhardtii, which is a well-established model for hydrogen production studies [13]. T. subcordiformis was observed to produce hydrogen with carbonylcyanide m-chlorophenylhrazone (CCCP) added into the seawater [12], whereas C. reinhardtii produced hydrogen in sulfur-deprived media [13]. T. subcordiformis algal cells have been used for stable hydrogen production of more than 50 mL/L [14], however, the yield and the duration of hydrogen production from T. subcordiformis were lower than those from C. reinhardtii [13].…”

Preparation of a microalgal photoanode for hydrogen production by photo-bioelectrochemical water-splitting

“…The photosynthetic capacity of algal cell was measured by a chlorophyll fluorometer (Water-PAM WALZ, Germany) with the pulse-amplitude-modulation (PAM) [9].…”