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Abstract

Chlorella zofingiensis is a prospective microalgae because it is mainly ascarotenoid producer, such as astaxanthin. However, its carbohydrates could be also as promising source ofbioethanol. Furthermore, Nitrogen stress treatment is reported used for increasing both carbohydrate and carotenoid of some microalgae. Therefore, this study aimed to increase carbohydrate and carotenoid of microalgae C. zofingiensis by using low and high nitrogen excessin the growth medium. The mediums were consisted of local compound fertilizer (farmpion), urea and ZA with a ratio of 0.25:0.5:1(lownitrogen excess medium) and 0.5: 1: 2(high nitrogen excess medium). Its cells density, carotenoid, and carbohydrate were measured every day for 7 days. The cell density was calculated using haemocytometer under light microscope. The carotenoid was measured using spectrophotometer with absorbance at a wavelength of 470, 645 and 662 nm. The carbohydrate was measured using sulfuric acid method. The results showed that the nitrogen stress treatment was able to increase carbohydrates and carotenoids approximately twice in C. zofingiensisas culture as source of bioethanol and antioxidant.