Influence of environmental conditions on lipid accumulation by the alga Halochlorella rubescens

Abstract

Abstract Lipids from microalgae have been studied for their potential application in various industries, such as cosmetics, biofuel, pharmaceuticals and animal feed. This study investigates the effects of different aspects of cultivation conditions (pH, the combination of nitrogen and phosphorus sources and their concentrations, carbon dioxide (CO2) concentration and light intensity) on lipid content and formation kinetics of the alga Halochlorella rubescens in a tubular photobioreactor. The highest lipid content (38.45 ± 1.018%) and maximum biomass production (0.3468 ± 0.004 g L− 1) were achieved in nitrogen-depleted medium at pH 9, 15% CO2 and 4000 lux after optimisation using the one variable at a time (OVAT) approach. The application of Fourier Transform Infrared Spectroscopy (FTIR) confirmed the functional groups of lipids present in the wavelength range of 3012 − 2809 cm− 1 and 1745 − 1734 cm− 1. Use of the Leudeking-Piret model revealed that lipid production by H. rubescens is growth-associated under different cultivation conditions. Analysis of the lipids produced confirmed that the major fatty acids under optimum conditions were palmitic acid (C16:0), linolenic acid (C18:3n3), oleic acid (C18:1) cis and linoleic acid (C18:2) cis. The tubular photobioreactor was confirmed to be suitable for the cultivation of H. rubescens under optimal conditions, and the fatty acids produced are relevant both for biodiesel production and as an excellent source of polyunsaturated fatty acids suitable for human consumption.