Identification of Candida tropicalis BH-6 and synergistic effect with Pantoea agglomerans BH-18 on hydrogen production in marine culture.

A marine yeast was isolated from mangrove sludge and named Candida tropicalis BH-6. The optimum temperature and the initial pH value for growth of the isolated strain were 37 °C and 5.0, respectively. The strain had high salt tolerance and could survive at NaCl concentrations of 0-6 %. Additionally, the yield of hydrogen production by C. tropicalis BH-6 was only 66.30 ml/l. However, when the yeast was mixed with Pantoea agglomerans BH-18, hydrogen production increased significantly to a maximum of 1707.5 ml/l, which was 36.94 and 247.54 % higher than the monoculture of P. agglomerans BH-18 and C. tropicalis BH-6, respectively. Taken together, these results revealed that in mixed culture, the yeast strain isolated from the same ecosystem as P. agglomerans BH-18 likely consumed the organic acids produced by fermentation, thus eliminating the factor inhibiting hydrogen production by P. agglomerans BH-18. As a result, the yield of hydrogen production during mixed culture increased significantly.