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“To evaluate the quantitative and qualitative changes in amino acids related to internal nitrogen content and growth rate of Ulva ohnoi, the supply of nitrogen to outdoor cultures of the seaweed was manipulated by simultaneously varying water nitrogen concentrations and renewal rate. Both internal nitrogen content and

growth rate varied substantially, and the quantitative and qualitative changes in amino acids were described in the context of three internal nitrogen states: nitrogen-limited, metabolic, and luxury. The nitrogen limited state was defined by increases in all amino acids with increasing nitrogen content and growth up until 1.2% internal nitrogen. The metabolic nitrogen state was defined by increases in all amino acids with increasing internal Selumetinib nitrogen content up to 2.6%, with no increases in growth rate. Luxury state was defined by internal nitrogen

content above 2.6%, which occurred only when nitrogen availability selleck compound was high but growth rates were reduced. In this luxury circumstance, excess nitrogen was accumulated as free amino acids, in two phases. The first phase was distinguished by a small increase in the majority of amino acids up to ≈3.3% internal nitrogen, and the second by a large increase in glutamic acid, glutamine, and arginine up to 4.2% internal nitrogen. These results demonstrate that the relationship between internal nitrogen content and amino acid quality is dynamic but predictable, and could be used for the selective culture of seaweeds. Amino acids are the critical constituent in animal feeds, specifically the essential amino acids methionine and lysine, as these

are the “first” limiting amino acids in plant-based feed formulations (McDonald et al. 2002, Boland et al. 2012). Amino acids are also targeted as a feedstock for biorefineries in the bio-based chemical industry (Scott et al. 2007, Jung et al. 2013). In this scenario, it is the nonessential amino acids that are the preferred primary substrates for bio-based chemicals, specifically glutamic acid, which resembles many industrial intermediates (Lammens et al. 2012). The extraction SB-3CT and concentration of nitrogenous biochemicals is now proposed as a common value-added component of most biofuel conversion and modeling (Ragauskas et al. 2006). Together these applications promote the use of high productivity biological feedstocks for feed and bio-based chemicals before the remaining biomass is converted to a biofuel, for which algae have received much attention (Ragauskas et al. 2006, Rowbotham et al. 2012). However, relatively little is known about the relationship between internal nitrogen content, growth rate and the quantitative and qualitative changes in amino acids for algae (as it is for plants; see Steinlein et al. 1993, Heilmeier et al. 1994, Lipson et al. 1996), and, correspondingly, whether internal nitrogen content can be manipulated to maximize the yields of specific amino acids.