Isolation and Culture of a Thermophilic Fungus, Melanocarpus albomyces, and Factors Influencing the Production and Activity of Xylanase

Abstract

An uncommon thermophilic fungus, Melanocarpus albomyces, was isolated from soil and compost by incubating samples in a glucose/sorbose/asparagine liquid medium, followed by enrichment culture in medium containing sugarcane bagasse as carbon source. The culture filtrate protein of the fungus grown in the presence of bagasse or xylose hydrolysed xylan and some other polysaccharides but cellulose was not hydrolysed. High extracellular xylanase (EC 3 . 2 . 1 .8) activity was produced by cultures grown on xylose or hemicellulosic materials. The enzyme was induced in glucose-grown washed mycelia in response to addition of xylose or xylan but not by alkyl or aryl P-D-xylosides. Cultures produced higher enzyme yields in shaken flasks than in a fermenter. Gel-filtration chromatography of culture filtrate protein showed the presence of two isoenzymes of xylanase, whose relative proportions varied with the carbon source used for growth. The extent of hydrolysis of heteroxylans or the hemicellulosic fraction of bagasse by culture filtrate protein preparations was greater when the cultures had been grown on bagasse rather than xylose as the inducing substrate. The activity of xylanase preparations was increased when an exogenous P-glucosidase was added.

Production of a high level of cellulase-free xylanase by the thermophilic fungus Thermomyces lanuginosus in laboratory and pilot scales using lignocellulosic materials

“…The xylanases of several thermophilic or thermotolerant fungi, e.g. Malbranchea pulchella (Matsuo and Yasui 1985), Melanocarpus albomyces (Maheshwari and Kamalam 1985), S. thermophile (Durand et al 1984), Talaromyces byssochlamydoides (Yoshioka et al 1981), T. emersonii (Tuohy and Coughlan 1992), Thermoascus aurantiacus (Yu et al 1987) and Thielavia terrestris (Durand et al 1984) have been reported to be thermostable. Due to differences in the assay methods and substrates used, direct comparison of the xylanase activity and thermostability among various fungi is difficult.…”

Thermophilic Fungi: Their Physiology and Enzymes

“…coprophile (95), and H. insolens (183). In M. albomyces (156) and T. lanuginosus (98,99,206), xylanase, but little or no cellulase, was produced. Crude culture filtrates of these fungi can therefore be used for biobleaching of paper pulp.…”

“…Paper of inferior quality was an excellent carbon source and inducer for xylanase in Thermoascus aurantiacus (139), Humicola lanuginosa (13,15), and Paecilomyces varioti (144). In Melanocarpus albomyces (156) and Thermomyces lanuginosus (205), xylose, the pentosan unit of xylan, could also induce xylanase. Xylanases are often coinduced with cellulases by pure cellulose, as in T. aurantiacus (248), Chaetomium thermophile var.…”

“…Interestingly, some compost fungi are unable to utilize cellulose, for example, Thermomyces lanuginosus (55,115,204), Talaromyces duponti, Malbranchea pulchella var. sulfurea, Mucor pusillus (55), and Melanocarpus albomyces (156). The noncellulolytic species in compost can grow commensally by utilizing sugars released during the hydrolysis of hemicellulose and cellulose by the cellulolytic partner.…”

Temperature effect in the production of multiple xylanases by Aspergillus fumigatus

“…As most of the industrial processes where xylanolytic enzymes are used are carried out at high temperatures, thermostability is a desired property in these enzymes. The production of xylanases and β-xylosidases active and stable at high temperatures has been described in different species, such as Melanocarpus albomyces (MAHESHWARI and KAMALAM 1985), Thermoascus aurantiacus (GOMES et al 1994), Thermomyces lanuginosus (DAMASO et al 2000, SING et al 2000, Aspergillus sydowii MG 49 (GHOSH et al 1993), Aspergillus fumigatus and Humicola lanuginosa (KITPREECHAVANICH et al 1984), and Aspergillus sp. (CASTRO et al 1997).…”