Research on the manipulation of iron ions and alkalis in Chlorella vulgaris culture

Abstract

• The experimental results shown that the variant concentration of iron ions in the medium and the variant pH of the initial algal fluid did different effects on the growth of Chlorella vulgaris . The Chlorella vulgaris can thrive better in the culture fluid with iron ions raising. The initial pH of the algae fluid affects its growth mainly in 1–3 days. Meanwhile, in a weak alkaline environment, such as pH 8.27 is beneficial to the growth of Chlorella vulgaris during the initial developing period. Also we find out in a certain range of alkaline environments such as pH 8 to 9 is the more conducive to its growth. By concluding the results of the research, we can obtain the optimal chlorella aquaculture production cultivation conditions with economic benefits. The use of microalgae as raw materials to produce various new biomass energy in the aquaculture industry has become a key issue in building a friendly ecology. However, maximizing algal growth and profit by regulating iron ion concentration (Fe 3+ ) and acid-base value (pH) remains a major challenge. Therefore, this study utilized Chlorella vulgaris to explore the influence of Fe 3+ concentration and initial pH value on algal growth to obtain optimum economic benefits and chemical culture conditions. Using an air-lift columnar photobioreactor for cultivation and a fluorescent lamp as a light source, the experiments were conducted at a light intensity of 3537 Lux at approximately 24 °C. To achieve economically optimal culture conditions, the daily OD 660 value of the Chlorella vulgaris cultures was used to explore the effects of different iron ion concentrations and initial pH values on algae growth and biomass accumulation. Our results demonstrated that different iron ion concentrations and pH conditions of the algal culture rendered different effects on Chlorella vulgaris growth. Overall, the enriched iron-containing medium was more favorable for algae growth. Over time, the medium with higher iron concentration (1.0 g/L) achieved higher OD faster and its accumulated chlorophyll was higher. Moreover, the initial pH of the algae culture medium affected its growth mainly within the first three days. Particularly, a weak alkaline environment (e.g., pH 8.27) benefited Chlorella vulgaris growth during the initial growth period. With the results of this study, our research determined the optimal Chlorella production conditions that maximize economic benefits.