Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/24/2008
Publication Date: 4/24/2008
Citation: Bang, S., Sani, R., Bleakly, B., Bischoff, K.M., Hughes, S.R., Wagschal, K.C., Wong, D., Lee, C.C., Jordan, D.B., Pokkuluri, R., Schiffer, M. 2008. Biofuels Group NSF DUSEL Project [abstract]. Homestake DUSEL Spring Workshop. Talk 10. p. 2. Interpretive Summary:
Technical Abstract: One of the major challenges in biomass degradation is its recalcitrance to chemicals or enzymes due to the presence of complex polymer composites consisting of cellulose, hemicellulose, and lignin. Recently, extremophiles isolated from deep subsurface, hot springs, and compost piles have shown high potential in degradation of recalcitrant biomass. Cellulose and hemicellulose degradation rates are significantly higher under thermophilic conditions than under the mesophilic, mainly because thermophile cellulases function well at relatively high temperature (50–70°C), where substrate solubility and mass transfer rates increase. During active mining operations over 125 years at the Homestake Gold Mine in Lead, South Dakota, surface microbes and lignocellulosic substrates were introduced into the extreme environments of the subsurface. Interactions between introduced and existing microorganisms through horizontal genetic transfer might have caused genome-altering events. It is therefore possible that genetically distinct microbes including thermophiles with diverse, novel metabolic activities might be present in the biofilms, decaying timbers, and soils of Homestake Mine. Thus, it is believed that DUSEL represents a potential source of high-value microbial enzymes (e.g. cellulases, xylanases, glucanases, peroxidases, amylases, proteases, and lipases) that have optimal activity at high temperatures. Several unique cellulose degrading thermophiles (60°C) have already been cultured from the DUSEL thermophile consortium collection. These pure cellulose-degrading isolates were identified using 16S rDNA sequence analysis and classified as Gram-positive bacilli. On the basis of our preliminary data, we propose to identify lignocellulose-degrading extremophiles from the deep mine (8,000 ft). It is generally accepted, however, that 99% of all microorganisms found in nature can not be cultured under laboratory conditions (Green and Keller, 2006). Therefore a metagenomic sampling could be the best way to identify novel cellulolytic and hemicellulolytic enzymes (Riesenfeld et al., 2004; Lammle et al., 2007). This research project addresses the need for development of novel technologies to overcome the recalcitrance of lignocellulosic feedstocks to depolylmerization for use in the fermentative conversion to biofuels. Specifically, we are proposing to isolate and identify novel efficient enzymes that degrade cellulose and hemicellulose from the unique ecological niche of the Homestake Mine. To accomplish this, the major research objectives include: 1) Isolate culturable deep-mine extremophiles that produce thermostable lignocellulosic hydrolases and high-value metabolites and byproducts. 2) Collect total DNA from unculturable organisms in deep-mine environmental samples. 3) Clone, sequence, and express genes for novel cellulases and hemicellulases from the resulting libraries. Crystalize the best structures and perform calorimetry to identify best changes.