Effect Of Iron On Enrichment And Nutritional Ingredients Of Chlorella Pyrenoidosa

Objective:To study iron on the growth of Chlorella pyrenoidosa and nutritional quality by adding different concentration of ferric chloride and ferrous sulfate to the medium.Methods:Chlorella biomass,content of enrichment,chlorophyll a,b,?-carotene,protein and soluble sugar were analyzed under different concentration of ferric chloride and ferrous sulfate.Results:When C.pyrenoidosa exposed to 25 ?mol·L-1 of Fe3+,the algae had the highest growth and biomass.The biomass and amount of enrichment were 5.595 mg·mL-1 and 99.51?g·g-1.Also,the contents of chlorophyll a,P-carotene,protein and polysaccharide had 75.2%,14.9%,11.7%and 15.9%higher than the control respectively.When the iron concentration increased to 50 ?mol·L-1,the growth and the physiological indexes were significantly lower than the control,and algae medium turned yellow and even the algae died.When C.pyrenoidosa exposed to 12.5 ?mol·L' of Fe2+,the algae had the highest growth and biomass.The biomass and amount of enrichment were 5.753 mg mL"1 and 53.25 ?g·g-1.The contents of chlorophylla,?-carotene,protein and polysaccharide had 81.8%,8.5%,16.7%and 22.1%higher than the control respectively.When the iron concentration increased to 50?mol·L-1,the growth and the physiological indexes were significantly lower than the control.The optimal concentration of Fe3+was 25 ?mol·L-1,which should be added day by day to the medium during the initial 5d of culture.At this condition,harvested biomass and Fe3+enrichment quantity of C.pyrenoidosa were 5.651 mg·mL-1 and 130.31 ?g·g-1,respectively,which had 5.4%,6.9%higher than those in one-time-added minner.Also,the optimal concentration of Fe2+ was 12.5 ?mol·L-1 that should be added day by day to the medium during the initial 5d of culture.At this condition,harvested biomass and Fe2+ enrichment quantity of C.pyrenoidosa were 5.568 mg mL-1 and 68.96 ?g·g-1 respectively which had 2.5%,3.8%higher than those in one-time-added minner.Based on the growth and nutritional quality,the comparision between Fe3+ and Fe2+ shows that chlorella cultured in 12.5 ?mol·L-1 Fe2+has the higher growth rate and better nutrient quality than those in 25 ?mol·L-1 Fe3+.At the same time,the biomass,contents of chlorophyll a,?-carotenc,protein and polysaccharide in 12.5 ?mol·L-1 of Fe2+were increased by 2.8%,3.1%,7.4%,6.4%,5.4%than those cultured in 25 ?mol·L-1 of Fe3+.Conclusion:The optimal concentration of Fe3+ and Fe2+ in medium were 25 ?mol·L-1 and 12.5 ?mol L-',respectively,which could stimulate the growth of Chlorella pyrenoidosa and improve the nutritional quality such as chlorophyll a,b,?-carotene,protein and soluble carbohydrate.When C.pyrenoidosa exposed to 25 ?mol·L-1 Fe3+and 12.5 ?mol·L-1 Fe2+with several times,the contents of biomass,enrichment,protein,polysaccharide were higher than those in one-time-added manner.Taking the cost and effect into consideration,Fe2+ may be the better choice for the cultivation of Chlorella pyrenoidosa.Because less Fe2+ can improve the nutrient contents,so the best choice is Fe2+ for Chlorella pyrenoidosa culture.