Abstract
The objective of this research was to investigate xylanase production by filamentous fungi (Trichoderma viride) to determine the best cultivation conditions in the process, aiming toward optimization of enzyme production. The best temperature, as well as the best carbon source, for biomass production was determined through an automated turbidimetric method (Bioscreen-C). The enzyme activity of this fungus was separately evaluated in two solid substrates (wheat and soybean bran) and in Vogel medium, pure and by adding other carbon sources. Temperature effects, cultivation time, and spore concentrations were also tested. The best temperature and carbon source for enzyme and biomass production was 25°C and sorbitol, respectively. Maximum xylanase activity was achieved when the fungus was cultivated in wheat bran along with sorbitol (1%, w/v), using a spore concentration of 2 x 106 spores.mL-1, pH 5.0, for 144 h cultivation. The study demonstrated not only the importance of the nature of the substrate in obtaining a system resistant to catabolic repression, but also the importance of the culture conditions for biosynthesis of this enzyme. T. viride showed a high potential for xylanase production under the conditions presented in these assays. Key words: Trichoderma viride, xylanase activity, enzyme optimization.
Highlights
Xylanases catalyze xylan hydrolysis, the major hemicellulose component in plant cell walls
Qualitative analysis of xylanase production by the evaluated fungi through the negative or positive growth in medium containing xylan as the sole carbon source (Table 1) was valuable regarding to make a previous evaluation of the producer fungi and afterwards the discharge of the non producers
The best carbon sources for the growth of each evaluated fungus are shown on Table 1, with glucose and maltose being the two carbon sources that showed the best results
Summary
The major hemicellulose component in plant cell walls. The hydrolysis of the xylan backbone is accomplished by endoxylanases (EC 3.2.1.8) and -xylosidases (EC 3.2.1.37) along with a variety of debranching enzymes, that is, -L-arabinofuranosidases, -glucuronidases and acetyl esterases (Collins et al, 2005). The enzyme is found in protozoa, insects, crustaceans, snails, seaweed, and seeds of plants during the germination phase in the soil (Wong et al, 1988)
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