Effect of lipid-free microalgal biomass and waste glycerol on growth and lipid production of Scenedesmus obliquus: Innovative waste recycling for extraordinary lipid production

In the present work, a novel approach of using growth medium with different substitutions of lipid-free algal hydrolysate (LFAH, 0, 5, 10 and 15%) and/or waste glycerol (WG, 0, 5, 10 and 20 g L^-1) for enhanced biodiesel production from Scenedesmus obliquus was studied. Combination of different concentrations of WG with 15% LFAH showed the maximum significant biomass productivity, which represented 27.4, 30.5 and 28.9% over the control at combined 5, 10 and 20 g L^-1 WG, respectively. The combinations of different LFAH with 20 g L^-1 WG showed the maximum significant lipid accumulation, where lipid productivity showed its maximum significant value of 59.66 mg L^-1 d^-1 using LFAH15-WG10. In addition, LFAH15-WG10 significantly enhanced total FAMEs yield by 21.2% over the control. Moreover, it reduced polyunsaturated fatty acids (PUFAs) ratio from 52.1% to 47.8% of total FAMEs, and increased monounsaturated fatty acids (MUFAs) ratio from 26.6% to 31.3% of total FAMEs.