Produção de celulases e xilanases por uma nova espécie fúngica - Achaetomium lippiae URM 7547 - utilizando a fibra de coco verde pré-tratada por explosão a vapor

Abstract

Endophytic microorganisms, which can be bacteria, fungi or protozoa, are poorly studied. It is estimated that there are more than 250,000 different species of plants and one million endophytes in the world, which characterizes an average of four associated species for each plant species. Because they are inside the plant, these microorganisms can be a rich source of biomolecules of industrial interest, such as the production of hemicellulolytic enzymes. In this context, this study was the first to study the endophytic fungal species Achaetomium lippiae URM 7547, with the objective of evaluating the production of cellulases and xylanases in submerged fermentation (FSm) using the fiber of pre-treated blast-treated green coconut husk as a substrate. Initially, the potential of A. lippiae URM 7547 to produce hydrolases (amylase, lipase, protease, cellulase, xylanase and pectinase) in solid culture media (72 h at 30 °C) with specific inducing substrates was evaluated. As a control, for comparison of results, growth of the fungus Thricoderma reesei CCT 2768 was used under the same induction conditions. A. lippiae URM 7547 presented itself as a potential producer of amylases, proteases and cellulases, with an enzyme index (IE) greater than 1.5, as well as T. reesei CCT 2768. The yield of substrate conversion into cell biomass (Yx/s) of A. lippiae URM 7547 and its maximum growth rate (µmax) in liquid medium containing glucose or xylose in three concentrations and nutrient medium with mineral sources were also quantified. and nitrogen in order to verify if the fungus is adept to submerged crops and what is the best condition for its growth. The best results for the liquid medium containing glucose were at 96 h of culture in the medium containing peptone and yeast extract, with Yx/s equal to 0.062 ± 0.04 g.g-1, 0.072 ± 0.04 g.g-1, and 0.076 ± 0.03 g.g-1, for the initial concentrations of 5, 10 and 20 g.L-1 of sugar, respectively. For the medium containing xylose, the best result was during 144 h of cultivation, with Yx/s values equal to 0.52 ± 0.08 g.g-1, 0.59 ± 0.09 g.g-1 and 0.65 ± 0.03 g.g-1 to 5, 10 and 20 g.L-1, respectively, in the same medium containing peptone and yeast extract. Finally, the pre-treatment of green coconut biomass and FSm were carried out for the production of cellulases and xylanases. The lignocellulosic characterization of green coconut fiber in natura and after pre-treatment by steam explosion indicated that there was a 14% decrease in extractables in the pretreated fiber in relation to in natura fiber, since these materials are easily removed by solvents. There was also an 8% increase in cellulose content and a 6% decrease in hemicellulose, while lignin remained statistically the same (p>0.05). In FSm, the conditions of 33 °C, initial concentration of 109 spores.mL-1, and 30.0 g.L-1 of pre-treated biomass were the ones that led to a better yield in relation to the four quantified enzymes, with enzymatic activities (U.mL-1) of 0.41 ± 0.06, 5.94 ± 0.31, 0.08 ± 0.03 and 9.12 ± 0.28 for FPase, CMCase, cellobiase and xylanase, respectively. Finally, A. lippiae URM 7547 proved to be a good producer of cellulases and xylanases, in addition to other hydrolytic enzymes such as amylases and proteases, with an excellent growth performance in submerged media.