Extreme Microbes Are Explored for Industrially Useful Enzymes

Enzymes from microbes that live at life's edges are beginning to find use in demanding industrial processes, according to work presented at last month's American Chemical Society national meeting in San Diego.

Because of their exquisite regio- and stereoselectivity, enzymes already find wide synthetic use in the food, detergent, paper, fine chemicals, and pharmaceuticals industries. But enzymes from organisms that live at extremes of temperature or pH may be better suited to the often-harsh conditions of such industrial processes, according to Garo Antranikian of Technical University Hamburg-Harburg, in Germany, one of several scientists who discussed their efforts to harness extremophilic organisms for industrially useful enzyme catalysts in a symposium organized by the Biotechnology Secretariat.

Antranikian reported that he has isolated a lipase from a heat-loving bacterium that is likely to find industrial use. Lipases, which hydrolyze the fatty acid ester bonds of fats and oils, are currently used in fine chemicals synthesis and in fat and oil processing. He pointed out that the thermostable lipase has the advantage of being able to tolerate elevated temperatures (up to 80 ºC), at which many fats are more soluble. The thermostable lipase--which also tolerates a broad pH range and boasts high regioselectivity--has been patented by Denmark-based Novozymes, he told C&EN.

Enzymes adapted to a cold environment may also be industrially useful, according to Charles Gerday of the University of Liège, in Belgium. Gerday described biochemical and structural characterization of a cold-tolerant xylanase from an Antarctic bacterium. Xylanases are used in the baking industry to improve the texture of bread dough. Unlike currently used xylanases, Gerday's cold-tolerant enzyme shows high catalytic efficiency at the cool temperatures used for dough handling but can be rapidly inactivated during baking.

Heat-stable xylanases are also of industrial interest. San Diego-based Diversa introduced a heat-stable xylanase for use in the paper-processing industry last summer. At the meeting, Eric J. Mathur, Diversa's vice president for scientific affairs and molecular diversity, recounted the discovery of this enzyme from an uncultured microorganism living in a volcanic hot spring in Uzon Caldera, in far eastern Siberia. "We looked here because the conditions matched those required for chemical bleaching of wood pulp--high temperature and high pH," Mathur told C&EN. Diversa's xylanase uses nearly a third less chlorine dioxide than commercial chemical bleaching methods and is currently in large-scale mill trials, he added.