Evaluation of new xylanolytic-producing isolates of Aspergillus from Misiones subtropical rainforest using sugarcane bagasse

Abstract

Xylanases hydrolyse efficiently the xylan component of hemicelluloses into single xylose monomers. Hence, these enzymes are suitable to be applied in the bioconversion of lignocellulosic wastes such as sugarcane bagasse to improve the bioethanol process. Misiones rainforest in the northeast of Argentina has a huge biodiversity which becomes the most likely site to screen new fungal isolates for powerful xylanolytic enzymes. The aim of this work was to find efficient xylanolytic Aspergillus with low levels of proteolytic enzymes through the isolation and exploration of native fungi from Misiones. Fungi were isolated from different locations of this subtropical region and 25 Aspergillus isolates were screened based on their ability to produce xylanolytic and proteolytic enzymes. From the principal component and conglomerate analysis, six groups were discriminated. The most promising fungi presented the highest endoxylanase and β-xylosidase activities and the lowest proteolytic activities. These isolates were A. niger LBM 055 and A. niger LBM 134 which reached 29 and 27 UmL−1 of endoxylanases, respectively; 0.6 UmL−1 of β-xylosidases, no casein and very little gelatin proteases. This study proves that the search of new fungi from nature is an important strategy to find novel isolates with the ability to secrete high-performance xylanases and exploit these enzymes in the bioconversion of lignocellulosic wastes.