Extraction protocols for the quantification of phycobilins in aqueous phytoplankton extracts

摘要

Phycobiliproteins are light harvesting pigments in cryptophytes, cyanobacteria, and rhodophytes that allow these organisms to absorb light in the green and orange regions of the electromagnetic spectrum. Unlike chlorophylls and carotenoids, however, phycobilins are rarely quantified as part of routine photobiological studies because they require different extraction protocols. The objectives of this study were (1) to compare 10 existing methods to determine that with the highest extraction efficiency and (2) to determine the maximum time limit for the storage of phycobilins before degradation. Cells of the cryptophyte Rhodomonas salina and the cyanobacterium Synechococcus bacillaris were harvested either by centrifugation or filtration and then subjected to lyophilization, mechanical disruption, or freeze–thaw techniques. The extraction efficiency for pigments in cells collected on glass fiber filters was always <32 ± 5% and thus always significantly lower than in samples harvested by centrifugation, which had extraction efficiencies of 53 ± 6–98 ± 11%. Disruption of cells by freezing–thawing and sonication both resulted in significantly higher (ANOVA, p < 0.01) extraction efficiencies than disruption with a tissue grinder. Storage of samples at −80°C showed no significant pigment degradation over the course of 24 weeks.