Unlikely element turns up in Enzyme; Commercial Renewable Fuels might Ultimately Result

Tungsten is exceptionally rare in biological systems. Thus, it came as a huge surprise to researchers when they discovered this novel enzyme in hot spring-inhabiting bacterium, Caldicellulosiruptor bescii. This tungstoenzyme plays a key role in C. bescii’s primary metabolism, and its ability to convert plant biomass to simple fermentable sugars which could lead to commercially viable conversion of cellulosic (woody) biomass to fuels and chemical feedstocks, which could substantially reduce greenhouse emissions.

Cellulosic biomass’ advantage as a feedstock for fuel and chemical production is that it need not compete with food production for land. Its big challenge is that cellulose is highly resistant to enzymatic degradation.Most efforts to convert it to useful chemicals have involved energetically expensive pretreatment. Thus Department of Energy’s BioEnergy Science Center has been focusing on Caldicellulosiruptor species (“hot cellulose-breakers,”), which inhabit volcanic hot springs around the world.

They grew C. bescii under a variety of conditions, including directly on cellulose and plant biomass, and found that it always produced the enzyme, dubbed XOR, at high cellular concentrations under all growth conditions. They also tried unsuccessfully to grow “knock-out” mutants lacking a functional XOR gene. That result suggested, but does not prove that the enzyme is necessary for growth, said Adams.

And so far, the enzyme’s function has not been determined. “Elucidating that function will likely be essential if we are to fully understand the bacterium’s ability to grow on unpretreated plant biomass,” said Adams. That knowledge, he added, would make it possible to metabolically engineer C. bescii to produce fuels and other useful chemicals from such feedstocks. http://www.eurekalert.org/pub_releases/2015-08/asfm-uet081315.php