Thermophilic anaerobic degradation of microcrystalline cellulose using mixed culture enriched from anaerobic digestion sludge

Thermophilic anaerobic digestion (at 55˚C) of microcrystalline cellulose was investigated in batch experiments using microcrystalline cellulose as the sole carbon source and anaerobic digestion sludge (ADS) as the seed sludge. The original culture was able to produce 566.0 ml/l methane with 14.7% degradation of the substrate in 380 hours. In order to enhance the thermophilic degradation efficiency of the mixed culture, ADS was enriched at 55˚C for 18 days. The enriched consortium was able to degrade 100% cellulose in 140 hours with stable production of acetate (6770.2 mg/L), methanol (2674.3 mg/L) as the major products. 16S rDNA analysis of the enriched mixed culture revealed that the dominant members of the cellulose-degrading consortium fell into to the genus of Thermoanaerobacterium (4 clones out of total 9 clones), Bacillus (2 clones), Tepidiphilus (2 clones) and 1 unknown strain.