Standardization of growth parameter and protocol for extraction and purification of phycobili proteins from Nostoc muscorum (Cyanobacteria)
2006
Kaushik, B.D., Indian Agricultural Research Inst., New Delhi 110012 (India). Div. of Microbiology
From the initial screening of seventy strains of cyanobacteria, Nostoc muscorum was selected for the standardization of growth, pigment production and extraction of phycobilin pigments. Nostoc muscorum was reddish brown in color and rich in phycoerythrin content. The influence of environmental factors was studied on the production of phycobiliproteins and carotenoids. Total phycobiliproteins increased when the culture was grown at 30 deg C and with 10 m/air/sec/l, while the carotenoid content reached a maximum with 20 m/air/sec/l. Low light intensities (1 Klux) favored maximum phycobiliprotein production, while maximum carotenoids were produced at high light intensities (13-28 Klux). The organism exhibited complementary chromatic adaptation. The highest phycoerythrin concentration (140 micro g/mg dry biomass) was obtained with green light and phycocyanin with red light (30 micro g/mg dry biomass). Based on the PC/PE ration, N. muscorum belongs to Group 3 of Tandeau de Mansac's classification. Purification of individual fractions was done through salting out with 55% (NH4)2 SO4 precipitates greater 80% of each class of phycobiliprotein. Chromatography on DEAE cellulose - 52 columns gave pure phycoerythrin (PC) (A562/A280 = 8.12), while rechromatography of the blue coloured fraction from this column using a hydroxyapatite column yielded pure phycocyanin (PE) (A615/A280 = 3.89). SDS-PAGE analysis of purified PE and PC showed two polypeptides (approximately 19.4 and 16.9 kDa). PE was stable between pH 5-9. This protocol led to the production of pure PE (72%) and PC (39%). The pigments were stable in indigenous cool drinks.
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