Optimization of Laccase Production, and Characterization of Lignin Degradation Products by Fusarium oxysporum JUMAD-053

Abstract

The objective of this work was to optimize the culture conditions for laccase production in the presence of Kraft lignin by Fusarium oxysporum JUMAD-053, and to evaluate the biodegradation products of lignin. The fungal isolate that presented highest laccase activity had its production optimized by a statistical factorial design 33 in 15 experimental runs. F. oxysporum presented the highest constitutive laccase titer (5.37 U/mL). Statistical factorial design demonstrated a maximum laccase titer of 9.8 U/mL when assayed against ABTS under the conditions optimized: 1.125% (w/v) yeast extract, 0.5% (w/v) Kraft lignin and 10 days of cultivation. The maximum laccase titer when assayed on DMP was 8.4 U/mL, following the conditions optimized: 1.125% yeast extract, 0.25% Kraft lignin and 7 days of cultivation. The analysis of cultures led to identification of metabolites; two being aromatic: 2,6-dimethoxy benzoic acid and sesamin; also, fumonisin and long-chain fatty acids. As a result of the study, the maximum laccase activities of 9.8 and 8.4 U/mL measured from ABTS and DMP substrates, respectively. The search shows new sources of fungal laccase for obtaining new metabolites of biodegradation from Kraft lignin in culture medium.