Demonstration of sustained hydrogen photoproduction by immobilized, sulfur-deprived Chlamydomonas reinhardtii cells

It was demonstrated that immobilized, sulfur-deprived algal cultures can photoproduce H22. After identifying the optimal material and procedures for immobilization of Chlamyodomonas reinhardtii   at high cell density, we examined the effect of liquid mixing, sulfate content, acetate levels and light intensity on the H22-production activity of the culture. Our results indicate that (a) liquid mixing is important to provide homogeneous conditions for the immobilized culture; (b) sulfur deprivation is necessary for hydrogen production by immobilized cultures; and (c) high light intensity decreases H22 production. The maximum total volume of H22 produced by the system (160 ml of reactor volume) was 380 ml over 23 days, and the highest rate of H22 production observed was 45 ml day-1-1. Cell immobilization significantly increased the duration of the H22-photoproduction phase (up to 4 weeks), maintained specific rates of H22 photoproduction similar to those of suspension cultures and showed potential for large increases in H22 production.