Lutein production by Muriellopsis sp in an outdoor tubular photobioreactor

The effect of dilution rate, mixing and daily solar cycles on lutein and bi omass productivity of the green unicellular alga Muriellopsis sp. has been studied, throughout the year, in an outdoor tubular photobioreactor. Highes t productivity values, for both lutein (about 180 mg m(-2) per day) and bio mass (about 40 g (dry weight) m(-2) per day) were achieved on May and July. Values for the optimal dilution rate varied, being lower in May (0.06 h(-1 )) than in November (0.09 h(-1)). Similar values for photosynthetic efficie ncy (about 4%) were recorded throughout the year, indicating that optimizat ion of culture conditions was achieved for each experimental period. Along the daily solar cycle, there was a fast increase of lutein content of Murie llopsis sp. in response to irradiance during the early hours of daytime, wi th maximal lutein content (about 6 mg (g dry weight)(-1)) being recorded at noon, and decreasing slowly, thereafter. An increase in cell growth was ob served following the establishment of maximum lutein/chlorophyll ratio, whi ch might indicate a role for lutein in protecting cells from photodamage. ( C) 2001 Elsevier Science B.V. Al rights reserved.