H2O2 as a fungicide in the growth phase of green Haematococcus pluvialis

Abstract

One of the potential sources for bioenergy and biochemical products is Haematococcus pluvialis. However, these microalgae are vulnerable to chytrid infection when the cells are transitioning from the green flagellates' stage to the resting stage. As a result, the productivity of their biomass is low. The objective of this research was to evaluate the effects of hydrogen peroxide as the fungicide, including those which were combined with fluazinam, on the growth of H. pluvialis. The variables used in this research were the dose of H2O2, the combination with fluazinam, and the frequency of H2O2 treatment. The initial cell number of H. pluvialis was 5 104 cells/mL culture medium. The 5 different treatments were done, i.e., (1) 0.028 mL H2O2/L liquid culture dosed every day; (2) 0.028 mL H2O2/L liquid culture dosed every day for only 3 days and then every two days combined with single dose 0.5 ppm of fluazinam on the first day; (3) same as (2) but without combination with fluazinam; (4) 0.035 mL H2O2/L liquid culture dosed every day for 3 days then every two days combined with single dose 0.5 ppm of fluazinam on the first day; (5) same as (4) but without combination with fluazinam. As a comparison, there was also a culture without any treatment as a control. The culture which was treated with hydrogen peroxide 0.028 mL H2O2/L liquid culture dosed every day for only 3 days and then every two days at the 7th day showed the highest cell number (45 104 cells mL-1 ∼ 9 fold from the initial cell number), even compared to the culture without any treatment. In conclusion, the treatment with hydrogen peroxide is effective against chytrid infection. The combination with fluazinam does not affect more to the effectiveness of H2O2 as a fungicide. It looks that by adding fluazinam, the H. pluvial growth is depressed.