Optimization Of Culture Conditions Of Navicula Lenzi And Analysis Of Nutrition In The Cells

The growth of microalgae was affected by many factors, Navicula lenzi was cultured instationary culture by shaking bottles three times a day.The differences of the growth kineticscurve, specific growth rates and biomasses under the culture conditions of different media,temperatures, nitrogen concentrations,silicon concentrations,phosphorus concentrations,ferrite concentrations, salinities,illuminations were compared by using single factorexperiment. Products, harvested from the stationary phase culture under different cultureconditions, were analyzed on the contents of soluble protein, polysaccharide, pigments andlipid.Orthogonal experiments were designed and carried out for optimization of the cultureconditions of Navicula lenzi.The influence of medium density on the biomass, polysaccharides, pigments, crude fat ofNavicula lenzi was very significant（p＜0.01）.High concentrations of medium could promotethe growth and the accumulation of polysaccharides.The cell density, specific growth rate,biomass and polysaccharides reached the maximum of Navicula lenzi under six times of f/2medium.With the increase of the concentration of medium, the cell proteins, carotenoid, crudefat content decreased, the maximum was reached under f/2medium.The content ofchlorophyll reached the maximum under low concentration of medium.With NaNO3as nitrogen source, the impact of nitrogen concentration on the specificgrowth rate of Navicula lenzi was significant (p＜0.05) under low illumination. The celldensity and the specific growth rate increased with the increase of the nitrogen concentrationunder low illumination. The cell density and the specific growth rate reached the maximumunder1500mg/L NaNO3.Under high illumination, a certain concentration of nitrogenconcentration could promote the growth of cells. Too high (2000mg/L) and too low (100mg/L)of the nitrogen concentration were not conductive to the growth of Navicula lenzi.The celldensity and the specific growth rate reached the maximum under1500mg/L NaNO3.Thespecific growth rate of1500mg/L NaNO3was not significant than500mg/L NaNO3, andlower than1500mg/L NaNO3under low illumination. The content of polysaccharide reachedthe maximum under high nitrogen concentration (1500mg/L).The content ofproteins,pigments reached the maximum under500mg/L NaNO3.The influence of phosphorus concentration on the growth of Navicula lenzi was significant (p＜0.05) with KH2PO4as phosphorus source. High concentrations of phosphorus promotethe growth of Navicula lenzi. The highest cell density and the highest specific growth ratewere got from80mg/L and40mg/L KH2PO4. With the increasing of phosphorus concentration,the content of nutrition increased at first and then decreased. The maximal contents of themwere reached under40mg/L KH2PO4.The influence of silicon concentration on the growth of Navicula lenzi was significant (p＜0.05) with Na2SiO3as silicon source under low illumination. The cell density and the specificgrowth rate reached the maximum under200mg/L Na2SiO3. Low concentration of Na2SiO3was conductive to the accumulation of cellular nutrients. The content of proteins,polysaccharides reached the maximum under200mg/L Na2SiO3. The content of pigments andcrude fat reached the maximum under100mg/L Na2SiO3.In the range of illumination set by the experiment, Navicula lenzi grew normally during therange of1.8μmol·m-2·s-1~180μmol·m-2·s-1. The specific growth rate reached themaximum under36μmol·m-2·s-1. The influence of illumination on the growth and thecontent of nutrition was inconsistent. Low illumination (9μmol·m-2·s-1) could promote theaccumulation of nutrition.With ferric citrate as the iron source, the cell density and the specific growth rate reachedthe maximum under2mg/L ferric citrate. The influence of ferric citrate concentration on thephysical and chemical composition of Navicula lenzi was significant. When the concentrationof ferric citrate was2mg/L, the single cell proteins and polysaccharides were the highest. Thecontent of chlorophyll, carotenoids,crude fat reached the maximum under4mg/L ferric citrate.In the range of temperature set by the experiment, Navicula lenzi could grow normallyduring the range of15℃~28℃. The cell density, specific growth rate and biomass reached themaximum under18℃. The content of proteins, polysaccharides and pigments was high underoptimum temperature. The difference of polysaccharides between18℃and22℃was notsignificant. The difference of chlorophyll content among18℃,22℃and25℃was notsignificant. The low temperature could promote the accumulation of crude fat. The content ofcrude fat reached the maximum under15℃.Under the range of salinity set by the experiment, Navicula lenzi grew normally during therange of15‰~40‰. The cell density and the specific growth rate reached the maximumunder the25‰salinity. The difference between25‰and20‰was not significant. Effects of salinity on the growth and nutrient content of Navicula lenzi were inconsistent.32‰salinity was conductive to the accumulation of proteins, pigments and crude fat. The contentof polysaccharides reached the maximum under20‰.Among various factors set by the experiment, the effect of KH2PO4on the biomass was thegreatest, and then followed by illumination, NaNO3, Na2SiO3. The optimal combination ofculture conditions to obtain maximum biomass were500mg/L NaNO3,80mg/L KH2PO4,200mg/L Na2SiO3,36μmol·m-2·s-1illumination. Under this condition, the content ofnutrition was relatively high.