Avaliação do potencial biotecnológico de celulases do fungo Lasiodiplodia theobromae na hidrólise de tecido de algodão
Abstract
The textile industry generates millions of tons of waste that are discarded and
take about 20 years to be degraded in nature. The enzymatic hydrolysis of tissues has
been shown to be a good alternative for recycling these residues, but commercial
enzymatic cocktails, which are expensive, are generally used. This work aimed to identify,
purify, characterize from the biochemical and specificity point of view, cellulases produced
by the fungus L. theobromae, in addition to evaluating the viability of using enzymes in
the hydrolysis of 100% cotton fabric. For this, the fungus was cultivated at 28 ºC for 30
days in liquid medium in the presence of carboxymethylcellulose and its growth was
monitored through activity assays against filter paper as substrate using the DNS method
for measuring reducing sugars. Activity for total cellulases on the 10th day of culture
growth averages 5.89 IU mL-1. After the time, the crude extract was subjected to
precipitation with ammonium sulfate followed by molecular exclusion and ion exchange
chromatography. Thus, it was possible to purify three cellulases with activities for
endoglucanase (0.15 IU mL-1), exoglucanase (3.11 IU mL-1) and β-glucosidase (0.02 IU
mL-1) that have better activity at pH and temperature of 10 and 60 ºC; 11 and 80 ºC; 5 and
45 ºC, respectively. This is the first description of an exoglucanase from the fungus L.
theobromae. The best conditions for tissue hydrolysis were determined through factorial
analysis of the parameters [Enzyme], [tissue], pH, temperature and reaction time, and the
effects of chemical and physical pre-treatments were also evaluated. The highest
concentration of reducing sugars obtained was in tissue hydrolysis without pre-treatment
(approximately 7 mg/150 mg of tissue), while the highest post-hydrolysis mass loss was
obtained with physical pre-treatment (19.72%). One hypothesis for these results is that
soluble cellulose oligomers were released during hydrolysis. Compared to the literature,
the cellulolytic enzymes of the fungus L. theobromae present adequate activities to be
used in the hydrolysis process of 100% cotton fabric.
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