EFFECTS OF EXTRACTS OF ALNUS-GLUTINOSA SEEDS ON GROWTH OF FRANKIA STRAIN ARI3 UNDER STATIC AND FERMENTER CULTURE CONDITIONS

In the present study, the effect of Alnus glutinosa seed extract on th e in vitro growth of Frankia strain ArI3 was investigated under variou s culture conditions. Frankia filaments grown in static cultures showe d a very slow growth with doubling time of 12 days. However, under the same growth conditions but with seed extract added to the medium, the doubling time was reduced to 6 days. A further reduction in doubling time (2.5 days) was obtained without seed extract when Frankia strain ArI3 was grown in a fermenter with continuous stirring. Under these cu lture conditions, seed extract did not influence the Frankia growth ra te. In all our studies, Na-propionate was used as the only carbon sour ce. Gradual addition of Na-propionate to Frankia cultures in the ferme nter sustained exponential growth of the filaments over a prolonged pe riod. The complete consumption of Na-propionate was the limiting growt h factor under fermenter growth conditions. The mechanism of growth st imulation by Alnus glutinosa seed extract under growth limiting condit ions in static cultures and its possible ecological significance is di scussed.