Effect of type of nutrient media on the biomass and fatty acid profiles of microalgae (Chlorella spp.)

Abstract

Locally available nutrient materials (Cow dung, Soybean extracts and Diammonium Phosphate (DAP)/UREA) were used to prepare culture media for growing Chlorella spp. and compared to the commonly constituted Bold’s Basal Medium (BBM) as a control. Algae was cultured in 25L rectangular glass tanks with 24 hour illumination and aeration. Ammonia, pH and counts of algae cells/ml were recorded daily for 24 days. Chlorella spp. production rate, effect of intrinsic ammonia and pH on culture performance, duration of culture cycle and the di fferences in resultant fatty acid composition of the algae were tested. Results indicated a significant effect of culture media on the growth performance of Chlorella spp. (F = 3.42, P< 0.05), although the interaction between time (day) and nutrient media was also significant (F = 17.27, P< 0.05). Bold’s Basal Media had significantly lower mean abundance of Chlorella spp. per millilitre than all the other media (F = 20.65, 13.57±7.1×104, P< 0.05). However, Soybean media supported significantly higher densities of Chlorella spp. than other media (F = 20.65, 20.65, 21.53±7.4×104, P< 0.05). The abundance of Chlorella in DAP/UREA and Cow dung media did not differ significantly (F = 20.65, 17.01×104±4.3 and 18.43±6.0×104, P = 0.46 respectively). There was a notable positive effect of pH on growth of Chlorella whereas ammonia did not have much impact even at relatively high concentrations (236.095 mg l-1 in DAP/UREA). Of the fatty acids in Chlorella, polyunsaturated fatty acids (>40% of Total Fatty Acids) were predominant in all media. Monounsaturated fatty acids (MUFAs) were recorded low (