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Abstract
The study evaluated various process parameters for mannanase production using co-culture of Penicillium italicum and Trichosporonoides oedocephalis under solid state fermentation. Different fermentation parameters affecting enzyme production were optimized using one-factor-at-a-time approach. Mannanase production was conducted in mineral salt medium into which copra meal (defatted coconut residual cake) had been incorporated as the sole carbon source and enzyme activity was evaluated. Maximum mannanase activity (144.444 U/mL) was obtained after 96 h of incubation in solid state fermentation. Different agro-wastes were screened as carbon sources for enzyme production in comparison to locust bean gum (control). Among tested carbon sources, orange peels proved to be the best substrate for mannanase production. Ammonium nitrate was observed to be the best nitrogen source with highest activity of 84.444 U/mL out of all the nitrogen sources screened. Also, for enzyme production the optimum temperature and percentage moisture content were 30°C and 60%, respectively.
Keywords: mannanase, agro-wastes, process parameters, locust bean gum, carbon and nitrogen sources selection
Introduction
There is a considerable interest in the biological degradation of lignocelluloses as the most abundant reusable resources in nature and its potential for industrial application (El-Naggar et al., 2006). The main carbohydrate constituents of lignocellulosic materials (cellulose, mannan, and xylan) consist of chains of β-1,4-linked pyranosyl units, which can be substituted in various forms. The β-1,4- glycosidic bonds within the polysaccharide backbones are hydrolyzed by cellulases, mannanases and xylanases (Sachslehner et al., 1998; Lee et al., 2011). Various mannanases from Streptomyces spp. (Ademark et al., 1998; Takahashi et al., 1984), Bacillus spp (Phothichitto et al., 2006; Mabrouk and El Ahwany, 2008), Sclerotium rolfsii (Sachslehner et al., 1998), Aspergillus awamori (Kurakale and Komaki, 2001) and Trichoderma harzianum (Ferreira and Filho, 2004) have been produced, and some genes from Bacillus subtilis and Bacillus stearothermophilus encoding mannanases were also cloned, sequenced and expressed (Mendoza et al., 1995; Ethier et al., 1998). The two most important and representative hemicelluloses are the hetero-1,4-β -Dxylans and the hetero-1,4-β -D-mannans. Endo -D-mannanase (EC 3.2.1.78, mannan endo-1,4-β -D-mannosidase) cleaves randomly within the-1,4-β- D-mannan main chain of galactomannan, glucomannan and mannan (Lee et al., 2011).
There has been an increasing interest in the potential application of β-mannanases in the industry, because these enzymes play an important role in the bioconversion...