Influence of different concentrations of sodium bicarbonate on growth rate and chlorophyll content of Chlorella salina

Abstract

Chlorella salina was grown in enriched medium supplemented with different concentrations of sodium bicarbonate to study the influence of inorganic carbon (C) on its growth and chlorophyll content. Linear growth was observed on the treatment with 0.004 and 0.005 M sodium bicarbonate whereas exponential growth was observed in control and 0.001 to 0.003 M bicarbonate treatment. The growth rate was maximum in 0.005 M concentration with a 1/ln value of 0 .270 + 0.01 on 15 days of culture. Increase in growth was observed with the increase of concentration of sodium bicarbonate from 0.001 to 0.005 M. Growth rate in 0.005 M concentration was 70% more than that of the control. There was steady decline of photosynthetic pigments (chl a & chl b) in both control and treatment in the initial period of growth. The decline was up to 4th day in the treatments from 0.002 to 0.005 M concentration whereas it was up to 7th day in control and 0.001 M treatment. Chl b was found to be steady from 7th to 15th days of treatment. Maximum chl a was observed in 0.005 M treatment (7.9 μg/ml) on 15th day and minimum during 4th day of culture (0.6 μg/ml). Chl a to chl b ratio showed increase in all the treatments until 13 days of culture period. In control and lower concentration of Ci treatment, the ratio increased to more than 2 after 9th day, whereas similar observation was found on 4th day of culture in 0.004M and 0.005 M treatments. This result leads to the conclusion that there is a need to augment inorganic carbon along with the enriched medium during the initial period of culture of Chlorella salina to improve the specific growth rate.