Why Sequence Cellulose Degrading Bacteria?

One of the major DOE missions is the production of renewable fuels to reduce our dependence on foreign oil, and also to take the place of petroleum-based fuels as these resources dwindle. Biologically produced ethanol is one possible replacement for fossil fuels. Currently, ethanol is produced from corn starch, but there is much research into using lignocellulosic materials (those containing cellulose, hemicellulose, and lignin) as the raw material for ethanol production.

Ethanol production from cellulose requires several steps: pretreatment with steam, acid, or ammonia; digestion of cellulose to sugars; and fermentation of sugars to ethanol. The slowest and most expensive step is the breakdown of cellulose, chemically accomplished by cellulases. The second and third steps can be carried out simultaneously in a process called Simultaneous Saccharification and Fermentation (SSF). This prevents inhibition of cellulases by glucose and cellobiose. These two steps can also be combined in one organism in the Consolidated Bioprocess (CBP). CBP can be carried out by adding cellulase genes to fermenting organisms, or introducing a fermentation pathway to a cellulose-degrading organism.

JGI will be sequencing three phenotypically and phylogenetically diverse cellulose-degrading microbes to expand the repertoire of cellulases available for biotechnological production of ethanol. Byssovorax cruenta is a cellulolytic myxobacterium. Eubacterium cellulosolvens is a rumen bacterium from the family Eubacteriaceae of the class Clostridia. Cellvibrio mixtus is a multiple polysaccharide degrader from the family Pseudomonadaceae. Cellulolytic and other saccharolytic enzymes have already been identified from some of these organisms, and having the complete genome sequences available will speed up the process of characterizing new enzymes.

Principal Investigator: Iain Anderson (DOE JGI).

Program: CSP 2009