Abstract
Introduction: Some species of microalgae have the ability to produce high amount of carbohydrates, rather than lipids. The extracted starch obtained from the ultrasonic treated green microalgae has high level of antioxidant activities and in animal studies, the extracted starch from Chlorella vulgaris (C. vulgaris) exhibited anti-atherogenic, anti-cholesterolemic, anti-inflammatory and anti-tumour effects. The green microalga has been widely used as a food source containing a complete set of nutrients including carbohydrates, proteins, vitamins, and minerals. Aim: To optimise the microalgae culture medium to increase starch production for medicinal use. Materials and Methods: This study was conducted as a field, observational and experimental research. For this purpose, 5 mL of microalgae C. vulgaris, Scenedesmus dimorphus (S. dimorphus) and Scenedesmus quadricauda (S. quadricauda), in the test tube containing Bold’s Basal Medium (BBM). BBM and Z8 media were used to grow freshwater microalgae. Light absorbance, cell count and biomass of microalgae in these media were studied. The experimental design method based on Taguchi method was conducted for optimising medium for microalgae with highest starch production, with light intensity, nitrogen and phosphorus factors, in three levels (1, 0,-1). Results: Specific growth rates of C. vulgaris in the media BBM and Z8 were 0.075 and 0.055 d-1, and for S. quadricauda and S. dimorphus were 0.072 and 0.008; 0.038 d-1, respectively. Due to significant difference (p=0.034) between Z8 and BBM media, BBM was selected for growing C. vulgaris, S. quadricauda (p=0.308) and S. dimorphus (p=0.033). In addition, growth rate and starch production of desired microalgae were achieved. Starch content in S. dimorphus, C. vulgaris and S. quadricauda were 19%, 29% and 20% of biomass weight, respectively. Conclusion: It was found that starch content was increased with increasing light, reducing phosphorus and nitrogen in Chlorella and the results showed that C. vulgaris could be a good choice as a starter for producing starch for medicinal purpose