Temperature effect on production of hydrogen and oxygen byChlamydomonas cold strain CCMP1619 and wild-type 137c

Abstract

Photosynthetic water splitting for hydrogen and oxygen production is a promising biological process that converts sunlight into useful chemical energy. In green algae, this process becomes active when hydrogenase is induced. In this process, water is split into molecular oxygen, protons, and electrons by photosystem II (PSII). The electrons acquired from water splitting are transferred through PSII to photosystem I (PSI). At PSI, these electrons are further energized by the PSI photochemical reaction. The energized electrons emergent from the reducing side of PSI are transferred to hydrogenase via ferredoxin (Fd), and thereby utilized in a hydrogenase-catalyzed reaction, the reduction of protons and production of molecular hydrogen. The protons consumed in the reduction reaction are derived ultimately from water splitting. The net result of this process is cleavage of water to molecular hydrogen and oxygen. Hydrogenase is a key enzyme in the photoproduction of hydrogen. In multicellular algae and higher plants, this enzyme is lost or no longer inducible for photoproduction of hydrogen. This enzyme is, however, inducible for photoevolution of hydrogen in certain microscopic algae such as Chlamydomonas. However, not all species of Chlamydomonas have an inducible enzyme to produce hydrogen in the light. In the work described in thismore » article, a Chlamydomonas cold strain, CCMP1619, was assayed for its potential hydrogenase activity by measuring anaerobically induced production of dark- and light-dependent hydrogen. This cold strain was originally isolated from Lake Bonney (ice-covered), Antarctica, and known to grow at low temperatures. The effect of temperature on hydrogen production by CCMP1619 was compared with the wild-type Chlamydomonas st rain 137c. The results indicated that 137c and CCMP1619 contain inducible hydrogenase, and that temperature had a significant effect on the rates of hydrogenase induction and on the kinetics of hydrogen production.« less