Research Interests

Research in our laboratory involves the selection, characterization, and engineering of promising microorganisms and enzymes for environmental and industrial applications.

For the last few years, we have been studying bacterial laccases, enzymes with a a non-specific oxidation specificity (substrates are aromatics, such as polyphenols, methoxy-substituted phenols and diamines), that do not require the addition of expensive cofactors, and instead use the readily available oxygen as electron acceptor. Documented applications of these enzymes include polymerization of phenols, functionalization of natural polymers, delignification, textile dye bleaching, effluent detoxification, transformation of antibiotics and steroids.

We have undertaken a multidisciplinary study to understand the key structure-function determinants of laccases from bacterial origin. For example, through site directed mutagenesis we examined how replacing key amino acid residues affects enzyme properties. By elucidating important aspects of the stability and catalytic mechanism of laccases, we have highlighted the limitation of the traditional rational approaches for enzyme design. Our system for improving enzyme properties is therefore to resort to directed evolution techniques, followed by robotic high-throughput screening.

Simultaneously, we screened and characterized novel hyperthermophilic laccases; their superior stability compared with typically used enzymes offers new and interesting opportunities for biocatalysis.

On the technological side, we have focused on the biodegradation and biosynthesis of synthetic industrial colorants, namely the important azo and anthraquinonic dyes. From the 106 tons of synthetic dyes produced every year, over 10% is released in wastewaters, as stable organic pollutants. Resorting to biotechnology for the transformation of these dyes is both technically very attractive and, in the case of laccases, quite promising.

We have recently begun investigating the enzymatic bioconversions of lignin, the recalcitrant biopolymer that gives wood its strength, using phenolic or non-phenolic model compounds. In the carbon cycle, degradation of lignin is a limiting step and clean technologies to unlock lignin, and hence cellulose, as renewable sources of chemicals and fuels may have great importance in the future.

Selected Publications

  • Fernandes, AT, Pereira, MM, Silva, CS, Lindley, PF, Bento, I, Melo, EP and Martins, LO. 2011. The removal of a disulfide bridge of CotA-laccase changes the μs-ms time-scale dynamics involved in copper binding. J. Biol. Inorg. Chem. 16:641-651.

  • Mendes, S, Pereira, L, Batista, C and Martins, LO. 2011. Molecular determinants of azo reduction activity in the strain Pseudomonas putida MET94: Cloning and molecular characterization of an oxygen-sensitive azoreductase. Appl. Microbiol. Biotechnol. DOI 10.1007/s00253-011-3366-4

  • Correia, B, Chen, Z, Mendes, S, Martins, LO and Bento, I. 2011. Crystallization and preliminary X-ray diffraction analysis of the azoreductase PpazoR1 from Pseudomonas putida MET94. Acta Crystallographic section F Struct Biol Cryst Commun 67:121-3.

  • Mendes, S, Farinha, A, Ramos, CG, Leitão, JH, Viegas, CA and Martins, LO. 2011. Synergistic action of azoreductase and laccase leads to maximal decolourisation and detoxification of model dye-containing wastewaters. Bioresource Technol. 102: 9852-9859

  • Chen, Z, Durão, P, Silva, CS, Pereira, MM, Todorovic, S, Hildebrandt, P, Bento, I, Lindley, PF and Martins, LO. 2010. The role of E498 in the dioxygen reactivity of CotA-laccase from Bacillus subtilis. Dalton Transactions 39:2875-2882

  • Fernandes, AT, Damas, J, Soares, CM, Todorovic, S, Huber, R, Pogni, R and Martins, LO. 2010. The multicopper oxidase from the archaeon Pyrobaculum aerophilum shows nitrous oxide reductase activity. FEBS J 277:3176-3179

  • Bento, I, Silva, CS, Chen, Z, Martins, LO, Lindley, PF and Soares, CM. 2010. Mechanisms underlying dioxygen reduction in laccases. Structural and modelling studies. BMC Structural Biology 10:28.

  • Durão, P, Bento, I, Fernandes, AT, Melo, EP, Lindley, PF and Martins, LO 2006. Perturbations of the T1 copper site in the CotA-laccase from Bacillus subtilis: structural, biochemical, enzymatic and stability studies. J Biol Inorg Chem 11:514-26.

  • Fernandes, AT, Soares, CM, Pereira, MM, Huber, R, Melo, EP and Martins, LO. 2007 A robust metallo-oxidase from the hyperthermophilic bacterium Aquifex aeolicus. FEBS J 274:2683-94

  • Pereira, L, Coelho, AV, Viegas, CA, Ganachaud, C, Iacazio, G, Tron, T, Robalo, MP and Martins, LO. 2009. On the mechanism of biotransformation of the anthraquinonic dye Acid Blue 62 by laccases. Adv Synth Catal 351:1857-1865

For further information please visit ITQB laboratory's website

Contacts

Lígia O. Martins
PhD 1994 in Biotechnology , UTL, IST
Tecnologia Microbiana e Enzimática (PT)
Phone (+351) 214 469 534
Extension 1534
lmartins@ibet.pt