Isolamento de fungos produtores de enzimas lignocelulósicas em depósito de resíduos de madeira de Pinus sp.

Abstract

Microorganisms such as fungi, bacteria and yeasts are used in the most varied industrial processes, being present in the context of biotechnological development the last years. Taking into account the different biomes existing in the Brazilian territory due to its vast territorial extension and its heterogeneous climatic conditions, the possibility of finding new microorganisms in nature is very attractive. Thereby, it’s of fundamental importance to know the physical and chemical properties that compose each ecosystem so that one has the opportunity to select the organisms with the best characteristics according to the intended application. In this context, the lignocelullosic enzymes producers play an important role in the natural process of nutrient cycling, where they act in the degradation of the major compounds of the vegetable cell wall (cellulose, hemicellulose and lignin) into simpler compounds that can be applied in several processes. In the present work, microorganisms were prospected in a pine wood waste deposit of the company Águia Florestal, in order to isolate fungi that had positive results for the production of cellulolytic enzymes. It has been more than 20 years since the residues were deposited at the site, promoting a microbiota with a load of vegetal biomass components, which provides the necessary nutritional conditions for the development of fungi capable of secreting enzymes of the lignocellulolytic complex. Fourteen samples from different points of the deposit were collected at depths ranging from soil surface level up to 1,70 m, within a radius of approximately 10 meters. The initial isolation was performed by inoculating 1 g of each sample into Petri plates containing Manachini’s solution (KH2POH4 2,0 g, (NH4)2SO4 1,0 g, MgSO4.7H2O 0,1 g, Na2HPO4.2H2O 0,9 g, yeast extract 1,0 g) plus agar and supplemented with 0,5% (w/v) carboxymethylcellulose (CMC) and incubated for 7 days at 30ºC. After the incubation period, the plates were revealed using Congo red dye 0,1% (w/v). From the plates where there were indications of carboxymethylcellulose degradation fragments were removed and the replating procedures were performed in order to obtain the most homogeneous strains possible, resulting in 8 isolates. Using the cup plate technique, the enzymatic index and the growth rates of the 8 colonies were determined resulting in 5 isolates with E.I. > 2,0 at the end of 24 hours of incubation at 30ºC, which characterizes them as promising microorganisms for biotechnological applications. The highest growth rates were observed in the isolates that obtained the lowest enzymatic index, A1 and B1, with a mean of 0,12 cm/day.