Fed‐batch cultivation of methanobacterium formicicum and its fluorometric monitoring

Abstract

Fed-batch cultivation of Methanobacterium formieicum 15-281 was performed under substrate limiting conditions. Specific rate of culture growth amounted to 0.041 h-l, cell yield related to substrate was 0.6 mg proteine/mM formate. Significant increasc of coenzyme F,, content in cells depending on time of cultivation was observed. Increase of the fluorescence intensity of the medium was also observed with the accumulation of biomuss. These parameters were suggested for tracking culture growth. The possibility of application of fluorescent factors for methanogenic population control in the anaerobic digester is discussed. IntrodiictionMethane-forming bacteria are the last step i n a chain of organic waste decomposition occuring in the digester. To estimate methanogelis i n the consortium quantitatively, it is necessary t o find a method for evaluating either methanogenic biomass directly, or a parameter connected with it. Methanogenic bacteria differ from other members of the consortium by possessing coenzyme F,,, (CoF42,) which becomes fluorescent after oxidizing [l]. The structure of CoF,,, was determined and its biological function was partially clarified [2]. The method of biomass analysis on CoF420 content is relatively simple [3,4]. Of all methanogens species growing on H, + CO, mixture and on formate contain the greatest quantity of CoF,,, [5]. Among such species there are many representatives of the genus Methanobacterium, to which belongs formate-using species Methanobacterium formicicum. The strains JF-1 [6], MF [7] are well studied from the point of view of the physiology of growth. We report here about the investigation results of Methanobacterium formicicum strain 2-281. Materials and Methods Organisms and cultivation medium : Methunobacterium formicicum 2-281 (DSM 3722) was received from T. N. ZH~LINA [8]. Mineral medium contained the following components (in g/l) : NH,Cl -0.33; KH,PO, -0.33; MgCl, x 6H,O -0.33; CaCl, x 2H20 -0.33; KCl -0.33; HCOONa -5.0; Na,S x 9H,O -0.4. To the medium were also