Wang Chang-hai

Growth inhibition of the eight species of microalgae by growth inhibitor from the culture of Isochrysis galbana and its isolation and identification

A type of growth inhibitor was successfully isolated and purified from cell-free filtrates of cultural medium at the death phase of Isochrysis galbana, and its chemical structure was confirmed by the methods of FABMS, UV, 1H-NMR, 13C-NMR and 2D NMR, which was 1-[hydroxyl-diethyl malonate]-isopropyl dodecenoic acid, C22H38O7. The results showed that the growth-inhibitor strongly inhibited the growth of Isochrysis galbana, and the growth of the eight species of microalgae (Dunaliella salina, Platymonas elliptica, Chlorella vugralis, Nitzschia closterium, Chaetoceros muelleri, Chaetoceros gracilis, Nitzschia closterium minutissima, Phaeodactylum tricornutum) also could be regulated by the growth-inhibitor in a concentration-dependent manner. The further investigation found that the synthesis process of chlorophyll and protein in the cells of all test microalgae could be inhibited by the growth inhibitor, and the content of chlorophyll and protein significantly decreased.

Effects of Light Regime on Extracellular Polysaccharide Production by Porphyridium Cruentum Cultured in Flat Plate Photobioreactors

Light quality was a key factor for controlling the growth and polysaccharide production of microalgae. Growth and extracellular polysaccharide production by Porphyridium cruentum cultured in flat plate bioreactors were measured as a function of light wavelength and intensity. The growth rate and polysaccharide production of Porphyridium cruentum increased with enhanced of light intensity, however a light level beyond the saturation point inhibited the growth of microalgae. Here, Photon flux density of 80 mu E m-2 s-1 was the optimal light level for maximum biomass and polysaccharide production by Porphyridium cruentum. Continuous light radiation enhanced the growth rate, but the maximum polysaccharide production was obtained at the light-dark cycle of 18:6. It was found no significant difference in cell growth between different spectrums. Green light, natural light and yellow light were found more suitable for increasing polysaccharide production than blue light and red light.

Oxygen consumption, ammonia excretion, and filtration rate of the marine bivalve Mytilus edulis exposed to methamidophos and omethoate

In this study, the oxygen consumption, ammonia excretion, and filtration rate were monitored in Mytilus edulis in response to administration of the two pesticides, methamidophos and omethoate. Five sublethal concentrations (1, 10, 50, 100, and 200 µgL−1) were administered over 96 h. Oxygen consumption rates increased following administration of all concentrations of methamidophos for 96 h and to the lower concentrations of omethoate (1, 10, and 50 µg L−1) from 6 to 24 h. Over 24 h, oxygen consumption decreased significantly. Ammonia excretion rates were higher than the control after 36 h of exposure to methamidophos, while reduction was observed when M. edulis was exposed to omethoate. The O:N ratios increased when the animals were first exposed to these two pesticides and then decreased at all the concentrations. At the concentrations of 100 and 200 µgL−1, the O:N ratio was below 30 after 72 h. The filtration rate of M. edulis decreased with the increasing concentration of pesticide exposure.