Influence of the N:P supply ratio on biomass productivity and time-resolved changes in elemental and bulk biochemical composition of Nannochloropsis sp.

Abstract

This work reports for the first time the detailed impacts of dual nitrogen (N) and phosphorus (P) stress on growth dynamics and biochemical composition in the Eustigmatophyte Nannochloropsis sp. P-stress concurrent with N-stress had subtle effects on culture bulk biochemical composition, but negatively influenced biomass productivity. However, the N:P supply ratio can be raised to at least 32:1 without compromising productivity (yielding a maximum lipid content of 52% of dry weight and volumetric lipid concentration of 233 mg L(-1)). The maximum biomass and lipid yields per unit of cell-P were 1.2 kg DW (gP)(-1) and 0.54 kg lipid (gP)(-1). The P concentration of many common media is thus in surplus for optimal Nannochloropsis sp. biomass and lipid production, offering potential for significant savings in P usage and improving the sustainability of algal cultivation.

Quantitative Assessment of Microalgae Biomass and Lipid Stability Post-Cultivation

“…In the repeated experiment (results in Figures 2A and 3), the biomass used in these two experiments came from different production batches resulting in the differences in initial harvested percent FAME, which impacted the trend. Several factors during microalgae cultivation affect cell composition and lipid profiles (Mayers et al, 2014;Scholz et al, 2014), e.g., different lipids convert to FAME with different efficiencies (e.g., mono-glycerides yields 83.2% FAME, triglycerides yields 100% FAME and phospholipids yields 64.4% FAME) (Laurens et al, 2012). Regardless of the increments in percent FAME (% of total DW) observed in this study, the total lipid content per vial decreased with increase in temperature and was only maintained constant at low temperatures and short incubation times, thus confirming that temperature and time resulting from delays during harvesting can affect final biofuel potential.…”

Mechanisms of Phosphorus Acquisition and Lipid Class Remodeling under P Limitation in a Marine Microalga

“…Nannochloropsis spp. do not comprise any AP, still grow effectively in low-P i seawater, and have a P uptake probably due to PACP activities (Mayers et al, 2014;Cañavate et al, 2017a). Why the evolutionary shift from membrane-bound AP to extracellular PACPs occurred with a pH maximum of 5.5 and a very weak activity at pH 8.6 remains unresolved and merits further investigation (Lubian et al, 1992).…”

“…have been shown to accumulate TAGs, increasing their lipid content up to 50% of cell dry weight (Rodolfi et al, 2009;Mayers et al, 2014;Cañavate et al, 2017b). Low P content triggering TAG increase also is seen in the model algae C. reinhardtii and P. tricornutum, additionally replacing extraplastidial phosphatidylcholine (PC) by taxonomically specific betaine lipid (BL) classes such as diacylglyceroltrimethylhomoserine (DGTS; Iwai et al, 2014;Abida et al, 2015).…”

“…To capture the taxonomically diverse response and niche partitioning, studies include ecological successful algae, such as Emiliania huxleyi and Thalassiosira pseudonana (Lessard et al, 2005;Van Mooy et al, 2009), and algae featuring high resilience and lipid content during low P, like Phaeodactylum tricornutum and Nannochloropsis spp. (Rodolfi et al, 2009;Yang et al, 2013;Mayers et al, 2014;Abida et al, 2015). During these studies, focus is often on changes of long-chain fatty acids (FAs) and their contribution to lipid classes in specific pathways [OPEN] Articles can be viewed without a subscription.…”

Outdoor production of microalgae

“…The latter could very well be a different species with different characteristics. Literature suggests a maximal specific growth rate of 1.0 d -1 for the species used in this study [112]. In another study done by the authors a daily averaged nett growth rate of 0.8 d -1 was obtained during the cultivation of Nannochloropsis sp.…”