Abstract
Microalgae of the genus Porphyridium show great potential for large-scale commercial cultivation, as they accumulate large quantities of B-phycoerythrin (B-PE), long chain polyunsaturated fatty acids (LC-PUFAs) and exopolysaccharide (EPS). The present study aimed to adjust culture nitrogen concentrations to produce Porphyridium biomass rich in B-PE, LC-PUFAs and EPS. Porphyridium purpureum SCS-02 was cultured in ASW culture medium with low nitrogen supply (LN, 3.5 mM), medium nitrogen supply (MN, 5.9 mM) or high nitrogen supply (HN, 17.6 mM). HN significantly enhanced the accumulation of biomass, intracellular protein, B-PE and eicosapentaenoic acid. LN increased the intracellular carbohydrate and arachidonic acid content, and promoted the secretion of EPS. The total lipids content was almost unaffected by nitrogen concentration. Based on these results, a semi-continuous two-step process was proposed, which included the production of biomass rich in B-PE and LC-PUFAs with sufficient nitrogen, and induced EPS excretion with limited nitrogen and strong light.
Highlights
Porphyridium purpureum is a species of marine red algae in the Porphyridiophyceae family.It has received great attention in recent years because of its potential to produce B-phycoerythrin (B-PE), long chain polyunsaturated fatty acids (LC-PUFAs) and exopolysaccharides (EPS) which are excellent feedstock for food, nutraceuticals and pharmaceuticals [1,2,3]
Our results showed that the proportion of B-PE reached 82% of the total phycobiliproteins; this was the primary reason for P. purpureum having a purple-red appearance phycobiliproteins; this was the primary reason for P. purpureum having a purple-red appearance
Results reported by Guihéneuf and Stengel (2015) showed that nitrogen deficiency caused a strong decrease in growth performance of P. purpureum PLY#539, likely because nitrogen is an essential component of many key enzymes in microalgae [7]
Summary
Porphyridium purpureum is a species of marine red algae in the Porphyridiophyceae family. Many kinds of microalgae can change their biochemical composition or accumulate secondary compounds when under stress conditions, such as those of strong light intensity or nitrogen limitation [5,6] This provides a possible approach to the production of target biochemicals by changing the culture conditions. Contradictory results regarding the effect of low nitrogen concentration on EPA and ARA production have been reported in many of the previous studies [9,15,16] These changes in B-PE, LC-PUFAs and EPS concentrations resulting from the different nitrogen concentrations provide to be a theoretical foundation for the customised production of these three compounds. High yields of B-PE and LC-PUFAs from Porphyridium would likely accumulate under optimal culture conditions, such as those of sufficient nitrogen and low light intensity. EPS and LC-PUFAs from P. purpureum SCS-02 by adjusting the initial nitrogen concentration
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