Nitrogen recycling from fuel-extracted algal biomass: Residuals as the sole nitrogen source for culturing Scenedesmus acutus

Abstract

In this study, the reuse of nitrogen from fuel-extracted algal residues was investigated. The alga Scenedesmus acutus was found to be able to assimilate nitrogen contained in amino acids, yeast extracts, and proteinaceous alga residuals. Moreover, these alternative nitrogen resources could replace nitrate in culturing media. The ability of S. acutus to utilize the nitrogen remaining in processed algal biomass was unique among the promising biofuel strains tested. This alga was leveraged in a recycling approach where nitrogen is recovered from algal biomass residuals that remain after lipids are extracted and carbohydrates are fermented to ethanol. The protein-rich residuals not only provided an effective nitrogen resource, but also contributed to a carbon "heterotrophic boost" in subsequent culturing, improving overall biomass and lipid yields relative to the control medium with only nitrate. Prior treatment of the algal residues with Diaion HP20 resin was required to remove compounds inhibitory to algal growth.

Effects of sodium nitrate on the growth and proximate composition of the indigenous marine microalgae Tetraselmis chuii (Butcher, 1959)

“…Studies also reported that some species-Scenedesmus acutus, Chlorella vulgaris, Nannochloropsis sp. and Nannochloropsis oleoabundans-grow well in nitrogen-deficient environments by exploiting their intracellular nitrogen reserves, such as pigment-protein molecules (Gu et al, 2015); this result also supports the present findings (i.e. growing cell concentration under low concentrations of nitrogen).…”

Effects of nitrogen sources on cell growth and biochemical composition of marine chlorophyte Tetraselmis sp. for lipid production

“…It is known that not every microalga can utilize YE as both nitrogen and organic carbon sources efficiently. Gu et al (2015) reported that when supplying the same concentration of YE, a freshwater microalga Scenedesmus acutus actively utilized YE for growth, resulting in a very high cell concentration, up to 10.4 g L -1 . However, Chlorella and Nannochloropsis species showed an insignificant increase in cell concentration.…”

“…In the nitrogen deficient culture, Tetraselmis cells sustained the growth, resulting in a higher cell concentration than that in ammonium culture. Some species such as S. acutus, Chlorella vulgaris, Nannochloropsis sp., and N. oleoabundans were also reported to grow well in nitrogen deficient conditions utilizing their intracellular nitrogen reserves, such as pigment protein molecules (Li et al 2008, Gu et al 2015. Blue-green alga A. platensis was also known to degrade phycocyanin, and used it as a nitrogen source under nitrogen-limited conditions (Sassano et al 2007).…”

Cultivation of Scenedesmus obliquus in liquid hydrolysate from flash hydrolysis for nutrient recycling

“…This is consistent with results reported in the literature showing the capability of certain microalgal species to utilize simple organic forms (such as urea but also some amino acids) as nitrogen sources, both in autotrophic and heterotrophic cultivation mode (Markou et al, 2014). In particular, Gu et al (2015) also found that Scenedesmus acutus was able to assimilate nitrogen contained in amino acids, yeast extracts and proteinaceous algal residuals. Phosphorus consumption was also measured, verifying that its concentration was not limiting (Fig.…”