Comparison of wild-type and UV-mutant β-glucanase-producing strains of Talaromyces emersonii with potential in brewing applications

Abstract

A screen of 46 UV-mutant strains of the moderately thermophilic fungus Talaromyces emersonii yielded two mutants (TC2, TC5) that displayed gross morphological differences to the parent strain and enhanced activity against mixed linkage cereal beta-glucans. Activity against beta-(1, 3)(1, 4)-D: -glucan from barley (BBGase) was measured during growth of the mutant and wild-type strains on a variety of carbon sources, ranging from solka floc to crude cereal fractions. In liquid culture, TC2 and TC5 secreted 1.2- to 8.6-fold more BBGase than the parent strain and markedly less beta-glucosidase (exo-activity); enzyme levels were dependent on the carbon source. Cellulose induced high BBGase. However, beet pulp, wheat bran, carob and tea-leaves were cheap and effective inducers. T. emersonii wild-type, TC2 and TC5 crude enzyme preparations achieved similar end-points during the hydrolysis of commercial barley beta-glucan (13.0-16.9%), but were more active against crude beta-glucan from barley (16.0-24.2% hydrolysis). The products of hydrolysis were quantified by high-performance anion-exchange chromatography. Mash trials indicated that enzyme preparations from all three organisms effected a significant reduction in wort viscosity and residual mash beta-glucan. Finally, TC2 and TC5 produce more efficient beta-glucan-depolymerizing enzymes; and wheat bran and solka floc can be used to provide inexpensive and potent enzyme cocktails with potential in brewing applications.