Optimal conditions for maximized H2 yield from a new green algal strain Chlorella sp. KLSc61

Abstract

Hydrogen produced from microalgae is attracting the attention of scientists as a potential new ‘Bio-Circular-Green’ energy source. We screened a selection of naturally occurring algal strains for H2 yield as a basis for high yield development. The best strain was a new strain of biohydrogen-producing green algae from a fresh water source at King Mongkut's Institute of Technology Ladkrabang, Thailand. Using morphological and 18S rDNA sequencing analyses, this alga was identified and classified as Chlorella sp. KLSc61. When adapted cells in TAP-K medium (with starting pH at 9.0) containing 25 mM ethanol, with 54 μmol photons m−2 s−1 light, and incubated at 35 °C, Chlorella sp. KLSc61 showed a maximum H2 yield of 9,804 ± 469.5 μmol H2 mg−1 Chl at day 7. Under these conditions, the cells produced ~ 12.2 times more H2 gas than without optimization (753.0 μmol H2 mg−1Chl). Our optimized system also produced H2 at a rate 11–570 times greater than previously reported microalgae. Thus Chlorella sp. KLSc61 could be a viable strain for biohydrogen production as a clean future energy source.