Chlamydomonas strains respond differently to photoproduction of hydrogen and by-products and nutrient uptake in sulfur-deprived cultures

Abstract

Hydrogen is a renewable and clean energy carrier that can be generated from microalgae. This study aimed to investigate the hydrogen and by-product production and nutrient uptake by five different strains of Chlamydomonas, including a wild-type strain. Selected strains were cultivated in two phases under continuous illumination: the first step was to obtain biomass; in the second step, the biomass was transferred to closed anaerobic photobioreactors for hydrogen generation under sulfur deprivation. There was an effect of different strains of Chlamydomonas on hydrogen and fermentative metabolite production and nutrient uptake. Wild-type strain had the best hydrogen productivity (9.23 µmol H2 mg Chl a-1 h-1), followed by C. reinhardtii CC425 strain (3.45 µmol H2 mg Chl a-1 h-1) and this result was on average 16 and 6 times higher, respectively, than the other strains. Strains that produced less hydrogen had better ethanol production (average of 280.6 mg L-1). The CC425 strain presented the best nutrient uptake efficiency, mainly of phosphate (67%). The results confirmed significant differences in anoxic metabolism from sulfur-deprivation-induced and metabolic flexibility by Chlamydomonas genus. Although all strains generated products of interest, the species, different strains, and cultivation conditions must be considered according to the purpose of the study.