Biohydrogen production from engineered microalgae Chlamydomonas reinhardtii

The green microalgae Chlamydomonas reinhardtti is well-known specie in the terms of H2 production by photo fermentation and has been studying for a long time. Although the H2 production yield is promising; there are some bottlenecks to enhance the yield and efficiency to focus on a well-designed, sustainable production and also scaling up for further studies. D1 protein of photosystem II (PSII) plays an important role in photosystem damage repair and related to H2 production. Because Chlamydomonas is the model algae and the genetic basis is well-studied; metabolic engineering tools are intended to use for enhanced production. Mutations are focused on D1 protein which aims long-lasting hydrogen production by blocking the PSII repair system thus O2 sensitive hydrogenases catalysis hydrogen production for a longer period of time under anaerobic and sulfur deprived conditions. Chlamydomonas CC124 as control strain and D1 mutant strains (D240, D239-40 and D240-41) are cultured photomixotrophically at 80μmol photons m-2 s-1, by two sides. Cells are grown in TAP medium as aerobic stage for culture growth; in logarithmic phase cells are transferred from aerobic to an anaerobic and sulfur deprived TAP – S medium and 12 mg/L initial chlorophyll content for H2 production which is monitored by the water columns and later detected by Gas Chromatography. Total produced hydrogen was 82±10, 180±20, 196±20, 290±30 mL for CC124, D240, D239-40, D240-41, respectively. H2 production rates for mutant strains was 1.3±0.5 mL/L.h meanwhile CC124 showed 2-3 fold lower rate as 0.57±0.2 mL/L.h. Hydrogen production period was 5±2 days for CC124 and mutants showed a longer production time for 9±2 days. It is seen from the results that H2 productions for mutant strains have a significant effect in terms of productivity, yield and production time.