PRODUCTIVITY AND PHOTOSYNTHETIC EFFICIENCY OF SPIRULINA-PLATENSIS AS AFFECTED BY LIGHT-INTENSITY, ALGAL DENSITY AND RATE OF MIXING IN A FLAT-PLATE PHOTOBIOREACTOR

The effect of the rate of mixing on productivity of algal mass in rela tion to photon flux density and algal concentration was quantitatively evaluated in cultures of Spirulina platensis grown in a newly designe d flat-plate photobioreactor. Special emphasis was placed on elucidati ng the principles underlying efficient utilization of high photon flux density for maximal productivity of algal-mass. Whereas the rate of m ixing exerted little influence on productivity and photosynthetic effi ciency in cultures of relatively low algal density, its effect became ever more significant as algal concentration was increased. Maximal mi xing-enhanced cell concentrations and productivity of biomass were obt ained at the highest light intensity used. At each level of incident l ight intensity, maximum productivity and photosynthetic efficiency cou ld be achieved only when algal concentration and mixing rates were opt imized. The higher the intensity of the light source, the higher becam e the optimal culture density, highest algal concentrations and produc tivity of biomass being obtained at the highest light intensity used. The rate of mixing required careful optimization: when too low maximal productivity resulting from the most efficient utilization of light c ould not be obtained. Too high a rate of mixing resulted in cell damag e and reduced output rate.