The two groups of bacteria isolated from the digester during the anaerobic digestion include the acid-formers ( Bacillus, Escherichia, Clostridium, Klebsiella, Proteus and Bactetroides ) and a methane former Methanococcus species. The correct balance between tese two groups of microorganisms determines the successful operation of anaerobic digesters for biogas production .The methane formers