Effects of nitrogen and phosphorus limitation on lipid accumulation by Chlorella kessleri str. UTEX 263 grown in darkness

Abstract

Growing algae in darkness for biodiesel production eliminates the challenges of evaporation and light penetration reported for open ponds and the costs and fouling that plague photobioreactors. The current study demonstrated that Chlorella kessleri str. UTEX 263 could grow heterotrophically in the dark on pure sugars or lignocellulosic hydrolysates of plant biomass. Hydrolysates of a prairie grass native to Kansas, Big bluestem (Andropogon gerardii), supported the growth of C. kessleri in the dark. Nitrogen limitation stimulated the accumulation of biodiesel lipids by 10-fold in heterotrophic cultures grown on pure sugars or Big bluestem hydrolysate. Limiting P in the growth medium also was shown to increase cellular lipid accumulation in C. kessleri. Iron limitation was not sufficient to increase cellular lipid content. Crude biomass extracts may have levels of N that can't be easily removed, which are high enough to relieve N limitations in growth media. This initial study suggests that P might be more easily removed from biomass extracts than N for increasing cellular lipid production by nutrient limitation and further that native prairie grasses are potentially suitable as sources of lignocellulosic sugars.

Biotechnological Approaches for Biomass and Lipid Production Using Microalgae Chlorella and Its Future Perspectives

“…In addition to nitrogen starvation, various nutrient starvation methods also achieved lipid stimulation in Chlorella [ 19 , 117 - 119 ]. Recently, Sakarika and Kornoros optimized culture conditions for lipid accumulation under sulfur limitation, resulting in maximum total lipid content of 53.43% (DCW) [ 120 ].…”

“…Many studies have shown the importance of cultivation conditions for microalgal growth and lipid accumulation. Nutrients [ 19 , 20 ], high salinity [ 21 , 22 ], metal ions [ 23 ], light intensity, temperature, pH, and abiotic/biotic treatments are regarded as critical parameters for microalgal growth and lipid accumulation. This review presents updated research on Chlorella biomass and lipid production, published mainly in the last five years, and discusses the subsequent progress and perspectives.…”

A preliminary study of cost and energy analysis of bio-fuel production from microalgae cultivated in parboiled rice mill wastewater

“…Compared to unfavorable conditions, favorable conditions result in lower storages of lipid and carbohydrate. Thus, various studies emphasized that nutrient starvation, especially phosphorus limitation, significantly enhance the carbohydrate and lipid content of the biomass (Hanifzadeh et al, 2018, Rehman and Anal 2019, Shrestha et al, 2020. Hence, it is ideal to cultivate microalgae under optimal conditions and later expose them to unfavorable conditions such as nutrient starvation in order to increase lipid and carbohydrate content (Pokoo-Aikins et al, 2010).…”

Assessment of Microalgal-Bacterial Granular Sludge Process for Environmentally Sustainable Municipal Wastewater Treatment

“…In fact, the microalgae are able to initiate complementary metabolisms during natural day–night cycles; , for example, the storage compounds (e.g., glycogen and poly-P) produced during daytime can be utilized to support the microalgal growth during nighttime . Thus, microalgae may grow heterotrophically using an organic substrate under dark conditions with simultaneous ammonia and phosphorus removal. − In addition, the facultative bacteria may transform the complex organics to small molecular weight organic carbon sources for microalgal assimilation under dark conditions. These imply that a synergetic effect between microalgae and bacteria may exist even at night, while the performances and mechanisms of the MBGS process in wastewater treatment under dark conditions, including the mass and energy balance during varied natural day-night cycles, need further study.…”