A newly isolated green alga, Tetraspora sp. CU2551, from
Thailand with efficient hydrogen productฟTetraspora sp. CU2551 had the shortest doubling time when grown in
Tris-acetate-phosphate (TAP) medium under a light intensity of 48e92 mE/m2/s and
a temperature of 36 C. Hydrogen production increased with increasing pH from 5.75 to
9.30; however, almost no production was observed at a pH of 5.25. Addition of 0.5 mM
b-mercaptoethanol to the TAP medium stimulated hydrogen production about two-fold.
During the hydrogen production phase, the use of TAP medium lacking both nitrogen and
sulfur resulted in about 50% increase in the hydrogen production. This was in contrast to
only a small increase in the production when either nitrogen or sulfur was omitted in TAP
medium. The stimulation of hydrogen production by 0.5 mM b-mercaptoethanol under
nitrogen- and sulfur-deprived conditions occurred only when the cells were grown at
a light intensity lower than 5 mE/m2/s with no effects at higher intensities. Maximal
calculated hydrogen production, 17.3e61.7 mmol/mg Chl a/h, is a very high production rate
compared to other green algae and makes Tetraspora sp. CU2551 an interesting model
strain for photobiological hydrogen production.ion