Experimental Studies On The Extracellular Products Of Marine Microalgae

The extracellular products of 11 species of marine microalgae, such as exopolysaccharide (EPS), extracellular Carbon compounds, extracellular Nitrogen compounds were investigated in this paper.Exopolysaccharide secretion may be the result of overflow metablism, just as an excess amount of carbon dioxide fixed relative to growth requirement. The number of cells and EPS production were influenced by different enviromental factors. The exopolysaccharide production reached to the maxunum when the nature condition is set as: pH 8, temperature 22 ~C, illuminance 3500Lux, photophase 12L:12D. The optimal culture condition for growth is different as to different species. In addition, red or green light and low N or P nutrient can increase the excretion of EPS. The growth condition of diatom would also have some effect on exopolysaccharide content. In general, when the algae grew to stationary phase, the EPS was increased greatly. The culture solution with different density of algal cells exhibited antimicrobial activites.The contents of DOC and POC varied with light and temperature m the culture of Chaetoceros sp.. Generally, in 24 hours, the DOC in euphotic layer is higher in the daytime than that in the night time. According to our observation, they reach their maximum value in 24Abstract9hoursl3500Lux. While under the condition without light, both of them9keep decreasing. Also, the most rapid increasing rate was observed atthe temperature range from 25 ~C to 30 ~C. The Nitrogen content of the culture also changed with the growth phase of inicroalgae.The EPS of Coscinodiscus sp. was purified. The composition identified by Gel chromatography showed that EPS was composed mainly of Glucose, and may contain protein.