Research On The Conditions Of Culturing High Density And Adding Selenium In Accumulating Se-polysaccharide Of Porphyridium Sp.

Porphyridium sp. belongs to Rhodophyta, Bangiophyceae, Porphtridiales, Porphyridiaceae, or Porphyridium, which is a marine unicellar red algae rich in high value bioactive outcome such as phycoerythrin, PUFA, exopolysaccharide, etc. It has been attached great importance to its research and development in the field of microalgae biotechnology. The present study concerns an attempt to investigate the effects of different modes of culturing, concentrations and methods of adding inorganic form of selenium to the growth of Porphyridium sp., and Chla, selenium in the exopolysaccharide are observed. The results are as follows: (1) Four different modes of culturing affect the growth of Porphyridium sp. significantly. The growth of Porphyridium supplied with NaHCO₃ and KNO₃ has reached OD₅₆₀ 2.5, which are 6.3,1.7,1.6 times more than the ones under stillness, shaking, stirring with compress air, conditions. (2) Different Se (IV) concentrations also affect the growth of Porphyridium sp. significantly. The best concentration of Se (IV) is 0.50 mg·L^-1 for the growth of Porphyridium sp. The content of Chl a, biomass and the polysaccharide has been improved 26%, 39%, 28% and 29% respectively than that of control. The growth of porphyridium sp. is inhibited distinctly when the concentration exceeds 1 mg·L^-1. The wavelength of absorption peak, emission peak and excitation peak will not change whether adding Se (IV) or not, which will not influence the transfer of light energy. The peak values of Porphyridium sp. under 0.05, 0.50 mg·L^-1 Se (IV) are higher than those of control, however, the peak values of Porphyridium under 1.0,2.0,5.0 mg·L^-1 Se (IV) are lower than those of control. (3) The study of different methods of adding inorganic form of Se (IV) shows that the methods of adding Se (IV) concentration of 0.50 mg·L^-1 in the 11^th day is the best for the growth and will improve the percent of selenium in the exopolysaccharide. The cell density, contents of exopolysaccharide, Se (IV) concentration are better than the l^st day adding time 15%, 15%, 0.80% respectively. Time to time adding Se (IV) concentration of 0.50 mg·L^-1 has no affect on the growth of Porphyridium sp.. (4) On adding inorganic form of selenium, supplied with CO₂, the biomass, contents of exopolysaccharide and selenium have improved 169%-255%, 110%-146% and 6%-46% than those of control of not supplying with CO₂. (5) The best condition is stirred with compress air rich in pure CO2 by adding 0.50 mg·L^-1 Se(IV), one time adding to culturing high density Porphyridium sp. and accumulating Se-pollysaccharide in the exponential period.