Influence of different alkaline pH medium towards growth kinetics, lipid production and fatty acid compositions Halochlorella rubescens

Abstract

Most microalgae having high lipid content which can be induced by altering the environmental factors in cultivation. The present study investigates biomass and lipid production and fatty acid compositions from cultivation of Halochlorella rubescens (H. rubescens) in three different initial pH mediums (7, 8 and 9) via cubic tank using Bold Basal Medium (BBM). The highest biomass concentration and productivity were obtained at pH 9 (0.2964 ± 0.002 g L-1) and pH 7 (0. 1960 ± 5.77 × 10-5 g L-1d-1) respectively. The highest specific growth rate of H. rubescens was at pH 7. The growth kinetics study using the Logistic model yielded R2 values of 0.9174, 0.9833 and 0.9731 for pH 7, 8 and 9 indicating that the model was well fitted. The highest lipid content was observed at pH 9 (17.77 ± 0.403 %) followed by pH 8 (14.37 ± 0.403 %) and the lowest value at pH 7 (11.71 ± 0.403%). Qualitatively, the Nile red staining method was used to determine the presence of lipid at different pH when the log phase cell suspension is sampled. Fluorescence Transform Infrared Spectroscopy (FTIR) analysis detects the functional groups of lipid present in the extracts. The analysis of H. rubescens lipids shows that the major fatty acid compositions present are eicosanoic acid (C20:0), palmitic acid (C16:0), linoleic acid (C18:2) cis and oleic acid (C18:1) cis in the range of 23.9% -29.2%, 19.5% - 23.1%, 16.9% - 18.8% and 12.6% - 14.0% respectively.