Improved biohydrogen production by immobilized cells of the green alga Tetraspora sp. CU2551 incubated under aerobic condition

Abstract

The green alga Tetraspora sp. CU2551 was previously investigated and showed enhanced H2 production under anaerobic (Ar purged) conditions by cells immobilized in a calcium alginate matrix (Maswanna et al., Biomass Bioenergy 111:88–95, 2018). Here, we report successful H2 production in entrapped cells under aerobic conditions. The most favorable immobilization condition observed was 4% (w/v) final alginate concentration after gelation, 2.80- to 3.35-mm beads, and a biomass content of 0.125 mg DW mL−1 alginate. H2 production increased when the immobilized cells were incubated in S-deprived media which could be repeated up to six times when using refreshed media. After six cycles, the H2 production reached 12.8 ± 0.9 mL H2 25 mL−1 of medium, corresponding to a rate of 182 ± 20 nmol mg−1 DW h−1, which was significantly higher than previously observed for other microalgae. Thus, our results demonstrate a potential for photobiological H2 production using immobilized Tetraspora sp. CU2551 cells, grown under ambient aerobic conditions.