Biodegradação da lignina kraft: otimização da produção de lacase pelo isolado JUMAD053 e análise dos produtos por CLAE

Abstract

Lignin is a very abundant aromatic polymer in the biosphere where it represents about 30% of all organic carbon and is the main source of aromatic compounds in vascular plants. The valorization of this polymer has aroused the interest in the sustainable production of derivatives, since its degradation products have important industrial applications. The objective of this work was to optimize the culture conditions for laccase production in the presence of Kraft lignin by the fungal isolate JUMAD053 and to evaluate the products of lignin biodegradation. Forty-seven fungal isolates were evaluated for constitutive laccase production in liquid medium. The microorganism that presented higher laccase activity under the pre-established conditions had its enzymatic production optimized by a factorial design 33 in 15 experimental assays. It was varied the concentrations of yeast extract (0.5 to 3.0%) and Kraft lignin (0 to 0.5%) as well as cultivation period, from 4 to 10 days. Laccase activity was determined using the substrates ABTS and DMP. Subsequently, the selected isolate was cultivated according to the optimized conditions pointed by the respective factorial designs and the cultures were extracted with organic solvents and submitted to HPLC. Isolate JUMAD053 was selected because it presented the highest constitutive laccase activity (5.37 U/mL). Factorial design demonstrated a maximum laccase activity of 9.8 U/mL using the substrate ABTS under the conditions: 1.125% yeast extract, 0.5% Kraft lignin and 10 days of cultivation. The maximum laccase activity using the substrate DMP was 8.4 U/mL, following the conditions: 1.125% yeast extract, 0.25% Kraft lignin and 7 days of cultivation. The incubation of the microorganism under conditions optimized for ABTS led to the production of two possible products of Kraft lignin biodegradation, such as benzoic acid. Regarding the chromatograms resulting from the optimized conditions for assays with DMP, it was observed the production of another two compounds, possible products of Kraft lignin biodegradation. The profiles of metabolites obtained from the biodegradation of Kraft lignin validate the objectives of this work and base future experiments for lignin valorization.