Study on heterogeneity of beta-glucosidase from Aspergillus species by using counter-current distribution

beta-Glucosidase plays a key role in cellulose degradation by cleaving its cellobiose units to glucose. The heterogeneity of the enzyme has been studied earlier by isoelectric focusing and several isoforms were found in the culture filtrate of Trichoderma and Aspergillus species. An aqueous two-phase system is an alternative fractionation method in which proteins are separated according to their net charge and surface properties. A dextran 500-poly(ethylene glycol) 8000 system was used to study the distribution of beta-glucosidase of different origins. To investigate the heterogeneity of enzymes 56- and 145-step thin-layer counter-current distributions were carried out. beta-Glucosidase produced by Aspergillus niger and Aspergillus carbonarius has been shown to consist of at least three isoenzymes by applying this method. The three forms of A. niger show the corresponding partition ratios with G values of 0.13, 0.22 and 0.31; and A. carbonarius 0.14, 0.22 and 0.36, respectively. However, the relative amount of these isoforms differs strongly between the two microorganisms.