Metabolic modelling of syntrophic-like growth of a 1,3-propanediol producer, Clostridium butyricum, and a methanogenic archeon, Methanosarcina mazei, under anaerobic conditions.

Clostridium butyricum can convert glycerol into 1,3-propanediol, thereby generating unfortunately a high amount of acetate, formate and butyrate as inhibiting by-products. We have proposed a novel mixed culture comprising C. butyricum and a methane bacterium, Methanosarcina mazei, to relieve the inhibition and to utilise the by-products for energy production. In order to examine the efficiency of such a mixed culture, metabolic modelling of the culture system was performed in this work. The metabolic networks for the organisms were reconstructed from genomic and physiological data. Several scenarios were analysed to examine the preference of M. mazei in scavenging acetate and formate under conditions of different substrate availability, including methanol as a co-substrate, since it may exist in glycerol solution from biodiesel production. The calculations revealed that if methanol is present, the methane production can increase by 130%. M. mazei can scavenge over 70% of the acetate secreted by C. butyricum.