Characterization of the photosynthetic conditions and pigment profiles of the colour strains of Hypnea musciformis from field-collected and in vitro cultured samples

Hypnea musciformis (Wulfen) JV Lamour. is a species of great economic interest as it produces Κ-carrageenan and has shown biological activities against HIV and HSV viruses. This species displays different colour strains in its natural habitat, which may have implications for the biotechnological potential of the species. The aim of this study was to characterize the photosynthetic apparatus and pigment profile of three colour strains of H. musciformis (green, brown and red) in their natural habitat and in culture. Chlorophyll a fluorescence of photosystem II was measured with a pulse-amplitude modulated fluorometer and pigments were quantified by spectrofluorimetry (chlorophyll a) and spectrophotometry (phycobiliproteins). In the natural habitat, we detected significant differences between the colour strains for the following photochemical parameters: the green strain had a higher effective quantum yield (ΦPSII) than the red strain and a higher maximum relative electron transport rate (rETRmax) than the brown and red strains. Saturation irradiances were 1000 µE.m-2.s-1 (green) and 500 µE.m-2.s-1 (brown and red). Concerning in vitro culture, the green strain presented the lowest ΦPSII, rETRmax, and α rETR, while the brown strain presented the highest values for these same parameters. The chlorophyll a content of the cultured green strain was the lowest. The phycoerythrin contents of the three colour strains were unchanged by either natural of in vitro conditions: lower in green, intermediate in brown and higher in the red strain, ensuring the chromatic identity of the strains. Our results suggest that the green strain has a better performance when exposed to high irradiance, but a lower efficiency under low irradiance compared to the brown and red strains.

Growth and biopigment accumulation of cyanobacterium Spirulina platensis at different light intensities and temperature

In order to find out optimum culture condition for algal growth, the effect of light irradiance and temperature on growth rate, biomass composition and pigment production of Spirulina platensis were studied in axenic batch cultures. Growth kinetics of cultures showed a wide range of temperature tolerance from 20 ºC to 40 ºC. Maximum growth rate, cell production with maximum accumulation of chlorophyll and phycobilliproteins were found at temperature 35 ºC and 2,000 lux light intensity. But with further increase in temperature and light intensity, reduction in growth rate was observed. Carotenoid content was found maximum at 3,500 lux. Improvement in the carotenoid content with increase in light intensity is an adaptive mechanism of cyanobacterium S.platensis for photoprotection, could be a good basis for the exploitation of microalgae as a source of biopigments.