Photorespiration plays an important role in H2 production by marine Chlorella pyrenoidosa

Abstract

Marine Chlorella pyrenoidosa was previously reported to produce H2 under nitrogen-deprived condition. In this study, the role of photorespiration in H2 production by C. pyrenoidosa was investigated. It was found that the expression level of genes encoding three enzymes involved in photorespiration decreased, but the expression level of gene encoding glutamate synthase increased in nitrogen-deprived culture compared with control, indicating a complex adjustment of photorespiration activity during H2 production by C. pyrenoidosa. The use of a photorespiration inhibitor led not only to a decrease in H2 production by 15 % under nitrogen deprivation condition, but also to a 16 % decrease in O2 evolution in the complete medium. Moreover, it was demonstrated that the total photosynthetic oxygen evolution and Fv/Fm declined when photorespiration was blocked. This suggested that, the photorespiration pathway does not directly participate in the production of photosynthetic electrons and the transfer of hydrogen producing electrons. However, it played an important role in photoprotection of PSII during H2 production by C. pyrenoidosa, which enabled PSII to provide more photosynthetic electrons to hydrogenase.