Noncellulolytic fungal β-glucanases: Their physiology and regulation

A great deal of recent interest has been shown in the ability of some microbes to synthesize exopolysaccharides. Most attention has been directed toward the prokaryote producers, yet many filamentous fungi also produce exopolysaccharides that have chemical and physical properties of considerable commercial potential. Surprisingly little is known about how and why fungi overproduce these metabolites and how yields are affected by both the physical and chemical environments. This review attempts to critically appraise the current literature on fungal exopolysaccharides, considers their chemical diversity, and examines factors that seem to affect their production. Although much of the published work has been carried out with the α-glucan pullulan, there is considerable literature on the β-glucans and, hence, both of these are discussed.

Production of Pullulan and other Exopolysaccharides by Filamentous Fungi

Direct detection of β-1,3-glucanase isozymes on polyacrylamide electrophoresis and isoelectrofocusing gels

The beta-glucans different from cellulose are the most abundant class of polysaccharides. They are found in microorganisms and higher plants as structural entities of cell wall, as cytoplasmic and vacuolar reserve materials, and as extracellular substances. Enzyme systems capable to hydrolyze beta-glucans are produced by different microorganisms. The occurrence and nature of beta-glucanases and their substrates are reviewed. The regulation of biosynthesis of these enzymes, their properties, substrate and product specificities, mode of action and molecular cloning are described. The participation of beta-glucanases in the morphogenetic events of yeast cell is presented. The role and synergism of different types of 1,3-beta-glucanases in microbial cell wall lysis and the potential application for isolation of intracellular materials like proteins, carbohydrates, enzymes and as an analytical tool are discussed in the light of current knowledge.

Microbial beta-glucanases different from cellulases.

High 1,3-β-glucanase activity was detected during autolysis in a culture medium containing Penicillium oxalicum. It was due to the combined action of four enzymes. The purification process for the major enzyme produced a homogeneous band in the SDS polyacrylamide gel that corresponded to a molecular weight of 79 400 daltons. The enzyme pI was 6.3 and it was only active against 1,3-β-glucans, with a S0.5 of 0.23 mg ml−1 against laminarin. The enzymatic optima were found at pH 4 and 55°C, and instability was evident when pH and temperature were altered. The enzyme was not active against oxidated lamanarin and was barely inhibited by glucono-D-lactone. Hg2+, Ag+ and Fe2+ were effective inhibitors. The enzyme was adsorbed by concanavalin-A-sepharose.

Purification and properties of a 1,3‐β‐glucanase from Penicillium oxalicum autolysates

Penicillium oxalicum grown in a basal medium with different carbon and nitrogen sources, produced exo-and endo-1, 3- β -glucanase activities during the autolysis period. The levels of these enzymes were high in all the media studied. Exo-1,3- β -glucanase had an optimum pH at 5.5 and endo-1,3- β -glucanase at 45. Both enzymes were most stable at pH values between 3 and 7. Exo- and endo-1,3- β -glucanases had their maximum activity at 50 °C and were stable up to 40 °. K m values were 0.2 mg ml −1 for laminarin and periodate oxidized laminarin in all the media tested but V max values were different depending on the type of culture medium.

M.I. Pérez-Leblic

Papers

Characterization of 1, 3-β-glucanases produced during autolysis of Penicillium oxalicum in different culture media