Abstract
The indigenous cellulolytic fungus Trichoderma longibrachiatum (GHL) isolated from soil near an Algerian hot spring was used for the production of cellulases by submerged fermentation on Mandels medium with cellulose Avicel (1%) as the sole carbon source. Endoglucanase and filter paper activities of the wild-type strain ofTrichoderma were compared to the hypercellulolytic mutated Trichoderma reesei Rut C-30, in shake flask cultures at 35°C. After seven days of fermentation, T. longibrachiatum show equivalent activities than T. reesei (10.61 IU/ml of endoglucanase (CMCase) and 2.04 IU/ml of filter paper activity (FPA)). On the other hand, the ß-glucosidase activity of Trichoderma GHL was twice more important than that of T. reseei. The influence of inoculum size on cellulase activities did not prove significant differences in enzymatic activities for spore concentrations between 105and 108 spores/ml. The cellulases produced by the isolated strain were also characterized. The optimum temperatures were 55 and 60°C for endoglucanase and FPA, respectively. The endoglucanase was thermostable at 70°C after 5 h incubation, and it preserved 80% of the original activity. The half-life of the FPA appeared to be 3 h at 60°C. The endoglucanase was optimally active at pH 4.0, and the FPA was optimal at pH 4.0 and 5.0. These activities were stable at 50°C after 5 h incubation in a pH range of 3.0 to 6.0 and 4.0 to 6.0, respectively. These results suggest that the non-mutated strain T. longibrachiatum (GHL) should be an attractive producer for cellulases production. Key words: Cellulase, Trichoderma reesei, Trichoderma longibrachiatum, submerged fermentation, characterization.
Highlights
Abundant organic compound on earth (Coughlan, 1985)
In the aim of comparing the enzyme amounts produced by the isolated strain T. longibrachiatum (GHL) and the mutated T. reesei Rut C-30, fermentations were performed at 30 and 35°C in shake flasks, using an inoculum size of 107 spores/ml. as shown in Table 1 at 30°C, enzymes were produced slowly with the isolated strain, and they reached their maximum after 240, 168 and 192 h for Filter paper activity (FPA) (1.72 IU/ml), endoglucanases (10.37 IU/ml) and β-glucosidase (0.49 IU/ml), respectively
The overall cellulase activity was secreted in larger amounts after 48 h with the mutant strain T. reesei Rut C-30, while to achieve the maximum enzyme activities, it takes time for cultures almost equivalent to T. longibrachiatum, 192 h with FPA (2.78 IU/ml) and βglucosidase (0.62 IU/ml), and 240 h with endoglucanase (13.67 IU/ml), respectively
Summary
Abundant organic compound on earth (Coughlan, 1985). its turnover in the carbon cycle is of prime importance for all living organisms (Beguin and Aubert, 1994; Tomme et al, 1995). The major industrial applications of cellulases are in textile industry for “biopolishing” of fabrics and producing stone washed look of denims, as well as in house hold laundry detergents for improving fabric softness and brightness (Cavaco-Paulo, 1998). Novozymes Company describes the production of biofuel from agricultural waste and announced that the enzymes can produce ethanol at a price below $2 per gallon (www.bioenergy.novozymes.com). For this reason, research aimed at understanding and improving cellulase production is still a hot topic in cellulase research. The conversion of waste cellulose to glucose is still not commercially feasible To resolve these problems, one of the key issues is the generation of improved producer strains with higher specific activity and greater efficiency. The characterization of cellulases produced by T. longibrachiatum is described
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