The 1-to 2-h illumination of xylanase with visible polarized light (PL) prior to the action of that enzyme upon beechwood xylan significantly increased its activity. The activity only negligibly decreased on 3 months storage. The hydrolysis of xylan proceeded in three well-distinguished stages. In the first and fastest stage the effect of illumination was only slightly positive. The effect of the stimulation was noted in the second, slower stage. Enzyme stimulated with PL, preferably by means of the 2-h illumination, performed better than enzyme stimulated with nonpolarized light and non-stimulated enzyme. In the last, the slowest stage, the rates of the reaction were nearly the same using either stimulated or non-stimulated enzyme.
IntroductionRecent increase in interest is noted in various modes of applications of polarized light (PL). Physicians have found that illumination of burns (1, 2) and wounds (3, 4) with PL accelerated their healing, and eczema psoriasis ceased after exposure to PL (5). There are also some reports on a positive effect of PL upon biostimulation in human organism (6-8).Other effects of PL on the biology of living systems have also been described (9, 10).Polarized light also influences living processes in flora. Navez and Rubenstein (11) found that PL influences the hydrolysis of starch, an effect that was associated with the activation of hydrolases. Semmens (12), who observed the effect of moonlight upon starch hydrolysis, has interpreted that observation in terms of the polarized nature of moonlight.Recently, the stimulating role of white, linearly polarized light upon all R-amylase in starch R-amylolysis (13), chitosanase and chitinase in the degradation of chitosan and chitin, respectively (14), cellulase in the hydrolysis of cellulose (15), glucosyltransferase in the production of cyclodextrins (16, 17), and the modification of the physicochemical properties of cellulose (17, 18) has been demonstrated. In this paper an extension of the application of white, linearly polarized light for stimulation of xylanase on the degradation of xylan is presented.Xylan was selected for the study because it is one of the most abundant polysaccharides in nature. It consists mainly of linear chains of D-xylosyl residues (19). Hydrolysis of xylan involves two major types of enzymes: endo-1,4--xylanases and -xylosidases. Endoxylanases split nonselectively -1,4-linkages between xylosyl residues in the xylan chains, whereas -xylosidases release xylosyl residues only from the non-reducing ends (20). Complete breakdown of such complex structure as xylan requires additional involvement of a number of debranching enzymes, i.e., acetylxylan esterase, R-L-arabinofuranosidase, and R-glucuronidase (21), all removing xylan substituents.In recent years, xylanases attracted attention due to their application in the food, fodder, and pulp industries (22, 23). The pulp industry produces carcinogenic chlorinated phenolics released into the environment on the use of chemical bleaching agents. Pretreatment of pulp w...