THE EFFECT OF β-GLUCAN MOLECULAR WEIGHT ON THE SENSITIVITY OF DYE BINDING ASSAY PROCEDURES FOR β-GLUCAN ESTIMATION

An assay procedure has been developed for quantifying β-glucan, based upon its reaction with the dye Congo Red. The sensitivity of this method to changes in β-glucan molecular weight has been determined using β-glucans prepared from standard material by acid hydrolysis and comparison has been made with a Calcofluor-based method for quantifying β-glucans. The Congo Red assay was found to be optimally sensitive to β-glucans with molecular weights of approximately 2.5 × 105 Daltons, whereas the Calcofluor assay was most sensitive to β-glucans with molecular weights in excess of 5 × 104 Daltons. The purity of the β-glucan used during this investigation was determined using an enzyme-based procedure in which the polysaccharide was degraded to glucose by the addition of β-glucanase. The β-glucanase employed was partially-purified from Trichoderma viride cellulase using a novel batch ion-exchange method which is also described.