Optimization Of Culture Conditions For Protein Produced By Heterotrophic Chlorella

Microalgae contains abundant resources such as proteins,fatty acids and pigments,so that it has been widely used in energy,food,medical and other industries in recent years.As a commercial microalgae,chlorella is rich in high-quality protein and it has been listed as an ideal health food by FAO.In foreign countries,the production of algae protein has been commercialized and it is worth billions of dollars.Nevertheless,it is difficult to meet the market demand in China.It is due to the difficulty in producing and the high cost of natural nutrition models.Therefore,we can increase the production of algal protein through high-density and low-cost cultivation of chlorella.Then it can meet the market demand and promote the development of algal protein industry.In this experiment,chlorella was heterotrophic cultured.In the two directions of medium composition and fermentation condition,p H,inoculation quantity,carbon source and nitrogen source were optimized to improve the harvest of algae protein.Then 50 L fermenter was used for the small scale test.The main research contents and results are as follows:1.Effect of carbon source on the growth and protein content of chlorella: cheap carbon sources--cassava starch and corn starch were selected for hydrolysis,and both hydrolysates were used to culture chlorella.The results showed that cassava starch hydrolysate was a suitable carbon source.When the glucose concentration in the hydrolysate was 30 g/L,the algal protein yield could reach 1.45 g/L.2.Effect of nitrogen source on the growth and protein content of chlorella: five different nitrogen sources,such as maize pulp,urea,ammonium sulfate,ammonium nitrate and sodium nitrate,were selected for culture of chlorella.The results showed that ammonium sulfate was an appropriate nitrogen source.When the concentration was 3 g/L,the algal protein yield could reach 3.22 g/L.3.Effects of fermentation conditions on the growth and protein content of chlorella:six groups of different initial p H and five different inoculation volumes were selected forculture of chlorella.The results showed that when the initial p H value of the fermentation broth was 6.4,the yield of algal protein was the highest,which could reach 1.75 g/L.When the inoculation amount was 15%,the yield of algal protein was higher,which could reach1.16 g/L.4.Orthogonal experiment was carried out on the basis of single factor experiment,and the optimized results were as follows: initial p H value was 6.4,inoculation volume was 10%,the glucose content of cassava starch hydrolysate was 30 g/L,and the mass concentration of ammonium sulfate was 5 g/L.Under this condition,the algal protein yield could reach 4.91 g/L.After 50 L scale-up fermentation experiment,it was found that the optimized algal protein yield could reach 26.37 g/L,higher than the results recorded in the existing literature.