Thermophilic Fungi with Glucosidase and Proteolytic Activities

Abstract

The directed search for extremophilic producers in order to obtain hydrolytic enzymes with increased thermal stability has an unconditional practical potential for use in the food and feed industry to improve the quality of the final product. The aim of the work was to study the ability of collection strains of thermophilic fungi to show α-L-rhamnosidase, α-galactosidase, cellulase, β-mannanase, keratinase and caseinolytic activity. Methods. Micromycetes were grown under submerged conditions in test tubes at 42°C for 8–14 days. Enzymatic activities were studied in the culture liquid supernatant. p-Nitrophenyl-α-D-galactopyranoside, naringin, guar gum galactomannan and Na-carboxymethylcellulose were used as substrates to determine α-galactosidase, α-L-rhamnosidase, β-mannanase and cellulase activities, respectively. Casein and crushed defatted feathers were served as substrates for the determination of proteolytic activity. Results. The enzymatic activity of 50 strains of micromycetes belonging to 17 species was investigated. The studied group showed high activity: 94% of the strains had at least one, 34% – two, 26% – from three to five enzyme activities. The most active keratinase producers were Thielavia terrestris 1920 and 62, Rhizomucor tauricus 1909, Chrysosporium thermophilum 2050, Thermoascus thermophilus 92 and Thermoascus aurantiаcus 2052 (10–26 U/mL). The highest α-L-rhamnosidase activity was observed in T. terrestris 62 (0.35 U/mL), and carboxymethylcellulase activity −in Thermomyces lanuginosus 2046. Six strains showed α-galactosidase (0.05–0.2 U/mL) and four strains − β-mannanase (5–130 U/mL) activity. Conclusions. As a result new strains producing proteolytic and glycolytic enzymes were isolated among thermophilic micromycetes. Soil thermophilic micromycetes can be used as producers of proteolytic and glycolytic enzymes. Of particular interest are the cultures of Acremonium thermophilum 1963, Corynascus thermophilum 2050, C. sepedonium 1899 and 65068, T. thermophilus 1946, which are capable of producing complexes of proteases and glycosidases in the culture liquid. This indicates that these strains are promising for use as destructors in various technologies processing of complex raw materials.