Monday, April 19, 2010
LL Conference Facility (Hilton Clearwater Beach)
Caldicellulosiruptor obsidiansis is an extreme thermophilic Gram positive bacterium isolated from the hot spring Obsidian Pool, located in Yellowstone National Park . This bacterium is capable if utilizing a broad range of carbohydrate substrates especially hemicellulose and cellulose growing at 60-80 deg C. Fully instrumented fermentors were used to cultivate C. obsidiansis while growing on model substrates including cellulose (Avicel) and xylan from Birchwood in a mineral medium with define additives. These fermentations yielded predominantly acetate up to 5 g/L plus low levels of lactate and ethanol (<0.5g/L). While this thermophilic microorganism grows well on cellulose, its growth was stimulated by xylan yielding simultaneously xylan and cellulose consumption. Upon metabolizing a majority of the xylan, the microorganism continues cellulose utilize substrate in a non-growth mode producing primarily acetic acid as fermentation product. Transferring an inoculum from batch fermentor to batch fermentor over a period of 17 days permitted selection of an adapted strain able to produce over 50% more acetate than the original parent. The nature of the apparent acetate tolerant strain is under investigation as a potential inhibitor resistant variant.