2.5. Biomass composition
After 14 days of experimentation, the cells were removed by means of centrifugation (16,000g at 25 C), and dried at 60 C until a constant weight was achieved. The dried biomass was analyzed for chlorophylls, carbohydrates, proteins, ash and lipids.Chlorophylls were extracted with 90% acetone and quantified using the equations suggested by Strickland and Parsons [6]. Lipids were determined by extraction with methanol:chloroform 1:1, followed by a liquid–liquid extraction with hexane [7]. Ash was quantified by the AOAC 941.12 method, total carbohydrate by the phenol–sulfuric method [8] and proteins by the Lowry method [9]. Biomass was also quantified in terms of nitrogen, carbon,hydrogen and sulfur in a CHNS analyzer (Flash 2000 series, ThermoScientific).