THE EFFECT OF DIFFERENT PHOTON FLUENCE RATES OF BLUE-GREEN LIGHT ON THE BIOMASS QUALITY OF A COASTAL DIATOM IN PILOT-SCALE SEMICONTINUOUS CULTURES

Chaetoceros sp. was kept in 101 semicontinuous cultures, compatible wi th pilot-scale commercial production, with 50% daily dilutions. Lighti ng was continuous, with Cool white, or blue-green fluorescent lamps, a lone or with 6.5 mu mol m(-2) s(-1) of white light. For each type of l ight, cultures were stabilized at different photon fluence rates and s ampled three to five times for biomass analysis. Cell yields increased with photon fluence rates, up to 432-498 mu mol m(-2) s(-1) for white and between 498-565 mu mol m(-2) s(-1) for both types of blue-green l ight. Above these fluxes, yields were light-saturated or even photoinh ibited. For equal photon fluence rates cell concentrations were higher in white light, but biomass yields better in mixed blue-green. Chloro phylls a and c decreased with increasing light, while carotenoids show ed an opposite trend. Carbon sinks were not different at low photon fl uence rates of white and blue-green light, but the mixture of blue gre en light and white favoured lipogenesis over glycogenesis. At high pho ton fluence rates of blue-green light, proteogenesis increased dramati cally at the expense of lipogenesis and glycogenesis in pure and mixed blue-green light respectively.