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.