NOVELTY - Generating biogas from biomass in a fermentation reactor comprises adding a microorganism of the species Methanoculleus bourgensis to the biomass.    USE - The M. bourgensis or the culture of microorganism is useful for the fermentative production of biogas from biomass (all claimed), where biogas is methane.    ADVANTAGE - The economical method increases the yield of biogas i.e. methane.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 97.31% sequence identity with the nucleotide sequence of SEQ ID NO. 4;    (2) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 97.54% sequence identity with the nucleotide sequence of SEQ ID NO. 9;    (3) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 98.04% sequence identity with the nucleotide sequence of SEQ ID NO. 10;    (4) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 97.53% sequence identity with the nucleotide sequence of SEQ ID NO. 11;    (5) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 96.88% sequence identity with the nucleotide sequence of SEQ ID NO. 12;    (6) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 99.1% sequence identity with the nucleotide sequence of SEQ ID NO. 28;    (7) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 95.82% sequence identity with the nucleotide sequence of SEQ ID NO. 27;    (8) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 95.88% sequence identity with the nucleotide sequence of SEQ ID NO. 20;    (9) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 99.63% sequence identity with the nucleotide sequence of SEQ ID NO. 25;    (10) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 99.26% sequence identity with the nucleotide sequence of SEQ ID NO. 26;    (11) a microorganism with a nucleic acid having a nucleotide sequence, which contains a sequence region having more than 97.54% sequence identity with the nucleotide sequence of SEQ ID NO. 29; and    (12) a culture of microorganisms, for use in a process for the fermentative production of biogas from biomass, comprising the above microorganisms, where the microorganism is at least 104% of the total number of microorganisms present in culture, Where sequences not defined here may be found at ftp://ftp.wipo.int/pub/published_pct_sequences/publication.