Available online at www.sciencedirect.com Biomass and Bioenergy 26 (2004) 329–335 Eect of reducing the light intensity on the growth and production of chlorophyll by Spirulina platensis E.D.G. Danesi * , C.O. Rangel-Yagui, J.C.M. Carvalho, S. Sato Department of Biochemical and Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, University of S˜ ao Paulo, Av. Lineu Prestes, 580-B.16, S˜ ao Paulo 05508-900, SP, Brazil Received 29 October 2002; received in revised form 20 June 2003; accepted 14 July 2003 Abstract The inuence of light intensity reduction on Spirulina platensis cultivation was investigated, using urea and KNO3 as nitrogen sources. The reduction of light intensity from 5 to 2 klux was studied both on the 9th and the 13th day of cultivation. Increases of up to 29% in the total chlorophyll production were observed for the cultivations with light intensity reduction, in comparison with the cultivations carried out at xed light intensities. ? 2003 Elsevier Ltd. All rights reserved. Keywords: Spirulina platensis; Chlorophyll; Light intensity; Two-step cultivation; Fed-batch 1. Introduction Photosynthesizing microorganism cultures, like Spirulina platensis, can be an alternative source of proteins for food and feed purposes. Also, there is the possibility of obtaining other products like vitamins, lipids and pigments such as carotenoids, phycocyanin and chlorophyll [1]. Theuseof Spirulina sp. pigments, as colorings have been explored by pharmaceutical, cosmetic and food industries. Moreover, Spirulina sp. presents antioxi- dant and antimutagenic properties [2,3], thus favoring its use as a functional food. In this context, the incor- poration of Spirulina sp. biomass in food can provide not only color but also an increase in the nutritional value of the food. ∗ Corresponding author. Fax: 55-11-3815-6386. E-mail address: fbtfcf@edu.usp.br (E.D.G. Danesi). Chlorophyll a, due to its stability properties, has been widely used as a coloring. This substance is conventionally obtained from plants, in which occurs the synthesis of other kinds of chlorophyll. Therefore, adequate extraction and separation processes are re- quired for the utilization of chlorophyll from plants. The S. platensis, on the contrary, presents only chloro- phyll a on its composition. In addition, this microalgae presents one of the highest chlorophyll contents found in nature, corresponding to 1.15% of its biomass [1]. Based on these facts, the utilization of S. platensis for chlorophyll production can be considered an interest- ing alternative to be studied. According to some studies, the chlorophyll biosyn- thesis in Spirulina platensis can be improved based on the culture media composition. Nitrates, such as KNO 3 and NaNO 3 , are commonly used as a nitrogen source for S. platensis cultivation. However, Stanca and Popovici [4] have shown that the use of urea as a nitrogen source was benecial to cellular growth, 0961-9534/$ - see front matter ? 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0961-9534(03)00127-2