Night illumination using monochromatic light-emitting diodes for enhanced microalgal growth and biodiesel production.

The present study investigated the effect of monochromatic light-emitting diodes (LEDs) on the growth and biodiesel yield of the green microalga Scenedesmus obliquus. Different LEDs were applied individually or in combination during the night period. Among different individual treatments, red and blue illumination showed the highest biomass and lipid productivity due to stimulation of pigmentation and photosystem II, respectively. Microalgal growth, lipid production and biodiesel recovery significantly increased under combined blue-red illumination. In addition, saturated and monounsaturated fatty acids proportions increased in favor of polyunsaturated ones. Moreover, blue-red LEDs enhanced the net biodiesel energy output over the control. The total increase in net energy output represented 5.1, 3.8 and 10.8 MJ using red, blue and blue-red light, respectively. In conclusion, application of blue-red LEDs during the night period is an economical technology for microalgae cultivation, which might have a potential impact on the future of commercial biodiesel production from microalgae.

Evaluation of Chlorella sorokiniana isolated from local municipal wastewater for dual application in nutrient removal and biodiesel production.

The isolated microalga Chlorella sorokiniana BENHA721_ABO4 was grown in Bold's basal medium (BBM) as a control, municipal wastewater (WW), and wastewater enriched with BBM elements (WW+). Cultivation in WW+ showed the highest cell number which represented 25.3 and 47.3% over that grown in WW and BBM, respectively. However, rapid growth in WW+ was accompanied by significant reduction in lipid content. Due to lipid accumulation in WW, it showed the maximum significant lipid productivity of 16.2 mg L-1 day-1. Microalgae cultivation in WW for 10 days showed 74.2, 83.3, and 78.0% removal efficiency for NO3-N, NH3-N and TP, respectively. In addition, growth in WW significantly reduced polyunsaturated fatty acids by 36.0% with respect to BBM in favor of monounsaturated fatty acids. The present results confirmed that C. sorokiniana isolate BENHA721_ABO4 grown in secondary effluent municipal wastewater offers real potential for future application in wastewater treatment and biodiesel production.

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.