Investigação de fungos ligninolíticos na produção de lacase utilizando lignina kraft e borra de café

Abstract

The world is totally dependent upon aromatic chemicals, through which numerous industrial products necessary for our day-to-day living are provided, e.g., in pharmaceuticals, bulk chemicals for synthesis of other chemicals, etc.. Today the main source of aromatic chemicals are derived from fossil fuels. It is estimated that the extraction of petroleum will become impracticable over the next fifty years due to its depletion. Lignin is an abundant alternative resource in the form of plant biomass, which is only sustainable through plantation forests, or as by-product materials from plant biomass biorefineries. Such uses will preserve and keep native forests intact. Lignin is a natural biopolymer found in the cell wall of vascular plants, and is made up of aromatic (85%) and phenolic (15%) structures. Lignin is built up of repeat structures comprizing phenyl-propane (C6-C3) residues. This work aims to select the best fungal species available in Londrina-PR and surrounding biotopes for enzymatic production and substrate degradation containing Kraft lignin. The collected fungi were isolated, and underwent a screening process, evaluating the rate of inhibition, color change of the culture medium and two-dimensional density. The isolate with the best results (JUMAD 054) went to the next stages of cultivation, besides including a strain previously donated to the laboratory to serve as a parameter of analysis of enzymatic activity, Botryosphaeria rhodina. The submerged culture involved a liquid medium containing Kraft lignin and Vogel salts, after an incubation period a free cell extract was obtained which was quantified by oxidation using 2,2'-Azino-bis (3- Ethylbenzthiazoline-6-Sulfonic) (ABTS), however, it was not possible to obtain enzymatic activity in the analysis and culture parameters performed for the selected fungus. Solid-state cultivation containing coffee grounds, Kraft lignin and Vogel salts as substrate after an optimization process and 12 days of incubation showed a maximum activity of 118.660 U/mL on day 5 for isolate JUMAD 054 and one peak activity for B. rhodina fungus of 745,746 U/mL. Based on the results obtained, we suggest the continuity of the study with the analysis of the influence of more variables for the cultivation of ligninolytocos fungi using coffee grounds to obtain laccase.