Two-stage photo-biological production of hydrogen by marine green alga Platymonas subcordiformis

摘要

A marine green alga,Platymonas subcordiformis,was demonstrated to photobiologically evolve hydrogen (H_2) after the first stage of photosynthesis,when subjected to a two-phase incubation protocol in a second stage of Eb production: anaerobic incubation in the dark followed by the exposure to light illumination.The anaerobic incubation induced hydrogenase activity to catalyse H_2 evolution in the following phase of light illumination.H_2 evolution strongly depended upon the duration of anaerobic incubation,deprivation of sulphur (S) from the medium and the medium pH.An optimal anaerobic incubation period of 32 h gave the maximum H2 evolution in the second phase in the absence of sulphur.Evolution of H_2 was greatly enhanced by 13 times when S was deprived from the medium.This result suggests that S plays a critical role in the mediation of H_2 evolution from P.subcordiformis.A 14-fold increase in H_2 production was obtained when the medium pH increased from 5 to 8; with a sharp decline at pH above eight.H_2 evolution was enhanced by 30-50% when supplementing the optimal concentrations of 25 mM acetate and 37.5 mM glucose.