| Summary: | To improve biogas production from lignocellulosics, methanogenic microbial enrichments were prepared from moose rumen fluid, beaver droppings, and internal circulation (IC) reactor granules amended with cellulose, pine needles, lignosulphonate, tannic acid, and poplar hydrolysate. Tannic acid delayed methanogenesis compared to cellulose only enrichments, both by reducing initial rates (up to 50% in beaver dropping cultures) and increasing lag times (up to 50 days in moose rumen cultures). Biogas yields from poplar hydrolysate were 56 % by beaver droppings, 51% % by IC granules, and 31 % by moose rumen enrichments. Bacterial community profiles, determined via denaturing gradient gel electrophoresis (DGGE) showed divergent populations between enrichments. Enrichment on pine needles or poplar hydrolysate promoted bioconversion of post extraction wash (PEW), and beaver dropping enrichments fed pine needles equaled the yield (about 23%) from IC granules. Together, the DGGE and PEW results provide evidence of acclimatization to previously recalcitrant feeds.
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