VERTICAL THIN-LAYER PHOTOREACTOR FOR CONTROLLED CULTIVATION OF CYANOBACTERIA

Nostoc sp. was cultivated in an air-lift reactor with continuous recir culation of the head gas phase that aerated and agitated the cyanobact erial suspension at regulated flow rates. The supply of inorganic carb on for growth was coupled with pH control, in the range of 7.7 to 8.1, by intermittent sparging of CO2-head gas mixtures. The formation of i rregular bubbles with swirling motion at the photostage of the reactor promoted efficient CO2 transference in dense populations of Nostoc sp . (1.1 g/l) when bubbling at flow rates of 10 l/min. Biomass productiv ity was almost six-fold higher in the photoreactor (16.4 mg/l.h) than in a conventional system (2.8 mg/l.h). The exponential growth phase of cultures in the photoreactor amounted to 60% of the total growth peri od.