Streptomyces sp. PG-08-3 was isolated from the desert of Rajasthan, India. Pure culture of this organism produced 500 and 250 Umg^_1 of alkalo-thermostable mannanase (after 100 h) in Solid State Fermentation (SSF) of wheat bran and kraft pulp at the moisture ratio of 1:1.5 and 1:3 respectively. Ammonium sulphate saturated mannanase was optimally active at 75 °C and was 100% thermostable at 55 °C for 120 min and also retained more than 50% residual activity at 75 °C for 60 min. pH 8.5 was optimum for the enzyme activity and stable at pH range of 6.0-9.5 at 37 °C for 60 min. Enzyme activity was enhanced to 40% and 38% by 1 mM Ca²⁺ and Fe³⁺ respectively. Mannanase showed more than 80% and ~60% activity at 4 M NaCl and 3 M urea after 60 min at 37 °C . The Km and Vmax of mannanase were 0.83 mgmL^_1 and 1.33 Umg^_1mL^_1 respectively. Hydrolysis of locust bean gum to mannanase was maximally (400 µgmL^_1) obtained after 30 min of catalytic reaction by mannanase at 75 °C .

Hemicelluloses are complex polysaccharides, which are abundant in higher plant cell walls. Galactomannan, the major softwood hemicellulose, contains b-1, 4-linked D-mannopyranose and D-glucopyranose units. The residues in the main chain are partially substituted by a-1-6 linked D-galactosyl side groups. The complete enzymatic degradation of hemicelluloses involves several specific activities. Endo 1,4-b-D-mannanase catalyses the random cleavage of b-D-1, 4-mannopyranosyl linkages within the main chain of galactomannan, glucomannan, galactoglucomannan and mannan. b-mannan is an important structural component of some marine algae in endosperm of copra, ivory palm nuts, roots of konjac, seeds of guar (Akino et al., 1987) and beans of locust and coffee (Akino et al., 1988). Microbial species known to actively produce mannanases include Bacillus subtilis (Emi et al., 1972; Araujo and Ward 1990; and Mendoza et al., 1995), Aeromonas hydrophila (Ratto and Poutanen, 1988), Enterococcus casseliflavus (Oda et al., 1993), Pseudomonas sp. (Yamaura et al., 1990), Vibrio sp. (Tamaru et al., 1995) Streptomyces sp. (Takahashi et al., 1984), fungi (Reese and Shibata, 1965, Civas et al., 1984; Park et al., 1987; and Arisan et al., 1993). Mannanases are also distributed in higher plants and animals (Yamaura et al., 1990). Mannanases are useful in food industries for clarification of fruit juices, production of konjac, treatment of coffee beans (Hashimoto and Funkomoto, 1971; and Oda et al., 1993) and also in bleaching of kraft pulp (Clark et al., 1990). In these applications, enzyme thermostability and thermoactivity are factors. Thus, availability of thermostable and thermoactive enzymes involved in the hydrolysis of b-mannan-based natural polymers is necessary. Actinomycetes secrete a wide range of enzymes active against main lignocellulose constituents, such as xylanases (Lopez et al., 1998), cellulases, peroxidase and proteases. Streptomyces spp. are the most industrially important actinomycetes, due to their capacity to produce numerous secondary metabolites, particularly antibiotics. The ability of the actinomycete to produce enzymes, such as hemicellulases, with varied substrate specificities offers potential interesting use for industrial application. In the present study, an actinomycete with high productivity of mannanase was isolated from Rajasthan soil and was identified as Streptomyces sp. PG-08-3. The present study describes the production, partial purification and characterization of mannanase from Streptomyces sp. PG-08-03.

Life Sciences Journal, Solid State Fermentation, Streptomyces, Hemicelluloses, D-glucopyranose Units, Enzyme Thermostability, Mannanase Production, Penicillium Purpurogenum, Streptomyces Mannanase, Industrial Applications, Thermoactive Enzymes.