Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
The presence of lignin is a major limitation for the production of second-generation biofuel from lignocellulosic biomass. The discovery and characterization of microbes expressing lignin-degrading enzymes could provide a viable and more environmentally friendly biomass pretreatment process than current thermochemical methods. In addition to the well studied wood-rot fungi, some bacteria found in soil and in the gut of wood-eating insects also have the ability to break down lignin. In this study, 140 bacterial strains were isolated from the rainforest soils from the Tambopata National Reserve in Madre de Dios in Peru. Two isolates, B7 and C6, were selected on the basis of high laccase activity using the ABTS test. 16S rRNA sequence analysis indicated that B7 and C6 are most closely matched to Bacillus atrophaeus and Bacillus pumillus, respectively. The time course of ABTS activity exhibited by these isolates demonstrated that strain C6 has higher total and specific activity (intra- and extracellular) than does strain B7. The ability of the enzymes secreted by these bacteria to modifying or remove lignin in poplar biomass was investigated by inoculating strains B7 and C6 into rich and minimal media containing poplar biomass. LC/MS analysis revealed that both bacteria released a range of compounds from poplar biomass, some of which were then identified using LC/MS-MS. In addition, NMR analysis showed that there is reduction of lignin and carbohydrate from poplar biomass after inoculation with strain C6 in minimal medium. Thus, the enzymes from these strains may be suitable for biological pretreatment processes.