Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 22, 2006
Publication Date: September 22, 2006
Citation: Bischoff, K.M., Liu, S., Edrington, T.S., Hughes, S.R. 2006. Isolation of xylose-utilizing thermophilic bacteria from dairy manure compost [abstract]. Extremophiles 2006. p. 19. Poster P045. Technical Abstract: Lignocellulosic biomass, an abundant and renewable carbon source, has the potential to replace starch as a feedstock for the fermentative production of fuel ethanol and other value-added products. Extensive use of this feedstock is problematic, however, because hydrolysis of cellulose and hemicellulose yields a mixture of hexoses and pentoses, and commercial fermentation biotechnology is based on a relatively small number of microorganisms that are generally limited in their ability to utilize the pentose sugars. Moreover, the mesophilic growth conditions of commercial biocatalysts are not well-suited for the enzymatic hydrolysis of cellulose and hemicellulose, which is optimal at higher temperatures and lower pH. Dairy manure is rich in lignocellulosic material and the high temperature achieved during composting makes it an ideal reservoir to search for new biocatalysts that can efficiently utilize the sugars derived from biomass. Composted manure from a dairy farm in Texas was examined for thermophilic microorganisms capable of fermenting xylose, the most abundant pentose sugar found in hemicellulose. Xylose-utilizing bacteria were isolated by enrichment with xylose medium in static cultures maintained at 55 deg C, then plating on minimal salts agar medium supplemented with 0.05% yeast extract and 0.5% xylose. Forty isolates were picked for analysis. All forty were Gram-positive rods, and analysis of rDNA indicated they were closely related to Bacillus coagulans, which is a thermophilic and acidophilic species. The major fermentation product was L-lactic acid, with minor amounts of ethanol and acetic acid also produced. Optimal growth occurred in the range of pH 5.5 - 6.5. Because of their temperature and pH properties, these strains have the potential to be developed as biocatalysts for the conversion of agricultural residues into fuels and other valuable fermentation products.