Effect Of Nutritional And Environmental Factors On Chlorella Pyrenoidosa's Hydrogen Production

To solve the increasingly serious energy crisis, searching and developing green renewable energy is an urgent need for both governments and scientists. Microalgal hydrogen, because of its unique advantages of being clean and renewable, has been an important field of bio-energy development.Chlorella pyrenoidosa is a single-cell green algae belonging to Chlorella Chlorophyta. Our laboratory's early work has confirmed that the alga has the activity of hydrogen production (HP). This paper studied the effects of high temperature, nitrogen, manganese or sulfur deprivation and inhibitor (streptomycin) addition on C. pyrenoidosa's HP, investigated the alga's physiological response during the progress of HP as well. The results are as follows:(1) Short-term stimulation of high-temperature activated photosynthesis and respiratory electron transport chain of C. pyrenoidosa, which promoted the alga's HP efficiency. C. pyrenoidosa has the higher HP efficiency under 35℃for 2 h than other temperature treatments, the total hydrogen yield was 86.997μL H2/mg Chla, which was 13.18 times of control; Under the combined conditions of 35℃(2 h) and sulfur deprivation, the HP time could prolonged nearly 24 h compared with sulfur deprivation group, and the total HP yield was 43.618μL H2/mg Chla, which was 1.79 times of sulfur deprivation group.(2) Nitrogen, manganese or sulfur deprivation can all induced the alga's HP, but the efficiency of HP was maximum under nitrogen deprivation, and the total hydrogen yield was 88.613μL H2/mg Chla, which was 4.61,1.92,3.63 times of control, manganese deprivation, sulfur deprivation groups, respectively. By measuring the growth, the photosynthesis and respiration of the alga, it was found that manganese deprivation had less influence than nitrogen and sulfur deprivation on the growth, the photosynthesis and respiration of C. pyrenoidosa. Compared with the normal (nutrients sufficient), manganese and sulfur deprivation inhibited the photosynthesis and growth of the alga while bringing small impact on respiration. Nitrogen deprivation, however, greatly restrained the photosynthesis and growth while enhancing the respiration.(3) 600 mg/L streptomycin addition could strongly promote C. pyrenoidosa's HP efficiency, the HP time could last for 8 d, which was 2 d more than the control, and the total hydrogen yield was 354.541μL H2/mg Chla, which was 18.44,5.85 and 1.35 times of control,200 mg/L,1000 mg/L groups, respectively. Compared with the control,600 mg/L streptomycin addition inhibited the photosynthesis of alga meanwhile brought some inhibitions to its later period's growth.Those results suggest that the photosynthesis and HP of C. pyrenoidosa have been influenced by various factors. As an appropriate basic research, it is hoped that the work could provide clues for the further study on both the conditions optimization and mechanism of HP.