Abstract
In an attempt to construct superior Trichoderma harzianum isolates for improving β-glucosidase productivity, protoplast fusion technique was applied. After application of different mutagenic treatments, twenty mutants were chosen to be tested for their resistance or sensitivity against four antifungal agents. Out of them, four isolates were selected on the basis of their response to antifungal agents and their productivities of carboxymethylcellulase (CMCase) and β-glucosidase to be introduced into intraspecific protoplast fusion experiments using two different methods (PEG and electrofusion). Three crosses were carried out among the selected four isolates. Results showed that, the number of fusants obtained after electrofusion were more than those obtained after polyethylene glycol (PEG) method. In addition, high productivities of CMCase and β- glucosidase were obtained after electrofusion in the three crosses. The applied protoplast electrofusion method proved to be a good and effective method for obtaining T. harzianum fusants with higher productivity of β- glucosidase enzyme. Key words: Trichoderma, protoplast fusion, electroporation, β-glucosidase.
Highlights
Cellulose is one of the most abundant substrates available in nature; the potential importance of cellulose hydrolysis in the context of conversion of plant biomass to fuels and chemicals as well as cellulose hydrolysis represents one of the largest material flows in the global carbon cycle (Zhang and Lynd, 2004)
Four isolates were selected on the basis of their response to antifungal agents and their productivities of carboxymethylcellulase (CMCase) and -glucosidase to be introduced into intraspecific protoplast fusion experiments using two different methods (PEG and electrofusion)
Protoplast fusion is an effective tool for inducing genetic recombinations and developing superior hybrid strains in filamentous fungi (Mrinalini and LalithaKumari, 1998; Pe,er and Chet, 1990; Stasz et al, 1988)
Summary
Cellulose is one of the most abundant substrates available in nature; the potential importance of cellulose hydrolysis in the context of conversion of plant biomass to fuels and chemicals as well as cellulose hydrolysis represents one of the largest material flows in the global carbon cycle (Zhang and Lynd, 2004). Beta-glucosidase ( -Dglucoside glucohydrolase, EC 3.2.1.21) is one of the essential enzymes in the enzymatic conversion of cellulose. It is an important component of cellulase system. Members of the fungal genus Trichoderma are considered the main producer of extracellular cellulolytic enzymes. This fungus belongs to the fungi imperfecti and contains seven chromosomes (Mäntylä et al, 1992) or sex chromosomes (Herrera-Estrella et al, 1993). Trichoderma harzianum is well known as producer of cellulolytic enzymes that are extensively used for the degradation of cellulose in textile and paper industries, beside its use in wastewater treatment (Prabavathy et al, 2006a and b)
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