Stimulation of biomethanation by Clostridium sp. PXYL1 in coculture with a Methanosarcina strain PMET1 at psychrophilic temperatures

摘要

Bioaugumentation of low temperature biogas production was attempted by addition of cold-adapted Clostridium and a methanogen. A psychrotrophic xylanolytic acetogenic strain Clostridium sp. PXYL1 growing optimally at 20pC and pH 5p"3 and a Methanosarcina strain, PMET1, growing optimally on acetate and producing methane at 15pC were isolated from a cattle manure digester. Anaerobic conversion of xylose at 15pC with the coculture of the two strains was performed, and batch culture methane production characteristics indicated that methanogenesis occurred via acetate through 'acetoclastic' pathway. Stimulation studies were also undertaken to evaluate the effect of exogenous addition of the coculture on biogas yields at 15pC. Addition of 3 ml of PXYL1 at the rate of 12 x 10po CFU mlp# increased the biogas 1p"7-fold (33 l per kg cowdung) when compared to control (19p"3 l per kg cowdung) as well as increased the volatile fatty acid (VFA) levels to 3210 mg lp# when compared to 1140 mg lp# in controls. Exogenous of addition of 10 ml PMET1 inoculum at the rate of 6p"8 pl 10po CFU mlp# in addition to PXYL1 served to further improve the biogas yields to 46 l kgp# as well as significantly brought down the VFA levels to 1350 mg lp#. Our results suggest that the rate-limiting methanogenic step at low temperatures could be overcome and that biogas yields improved by manipulating the population of the acetoclastic methanogens. Stimulation of biomethanation at low temperature by coculture.