New thermostable enzymes for crop fractionation

Most industrial crop valorization methods employ an initial fractionation step. This is achived by physical, chemical or biological processes. Often, after a first physical step (milling in the case of wheat), a chemical or biological step will be sufficient to obtain the molecule of interest. However, most of the currently used processes employ high temperatures which are incompatible with a biological step. Nevertheless, some processes already use biological components. The best example is that of the starch process which involves the thermostable a-amylase from Bacillus licheniformis, which is active up to 100 degrees C. Recent developments in enzyme technology has permitted the identification of hyperthermostable enzymes from the new class of hyperthermophilic archaea (Pyrococcus and Thermococcus), coming from hydrothermal vents. In this report we examine the new possibilities for crop fractionation using these hyperthermostable enzymes. Our work has focussed on the starch process, in order to illustrate the industrial potential of these enzymes. Special emphasis is placed on an alpha-glucosidase and a pullulanase, enzymes necessary for the conversion of starch to glucose, which have been identified in a new Thermococcus strain. The pH optimum of these enzymes appear to be compatible with that of the B. licheniformis alpha-amylase. Finally, we discuss other thermostable enzymes that may find applications in the crop fractionation industry. (C) 1997 Elsevier Science B.V.