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Laccases are enzymes from the multi-copper oxidase family that have gathered a lot of attention due to their wide range of substrates, their interspecies variability and their still elusive mechanism of action. The presence of four copper atoms in their active site makes them an interesting model for the study of the relationship between the structure and function of proteins. It is possible to find them in fungi, plants and prokaryotes. Bacterial laccases display many advantages over fungal laccases in terms of their application. They have, in general, a greater thermal stability and a different pH profile, which contributes to widening their field of possible application. In the present work, a novel laccase from an Antarctic microorganism, Geobacillus sp. ID17, is purified and characterized. This is the first Antarctic bacterial laccase to be functionally described. It was found to be active at neutral pH and to have greater activity at 55°C. Its catalytic constants are in the order of other bacterial laccases. Screening for different potential substrates was also performed, showing that this novel laccase is more selective than commercial laccases. This enzyme could find potential application in the generation of gallic acid polymers or in organic synthesis in contexts where meticulous substrate discrimination is needed.

Violacein is an intensely purple pigment synthesized by various genera of bacteria that has been discovered to have a wide range of interesting biological activities which range from anticarcinogenic to antibacterial. One of the hindrances for its real-life application is that the first microorganisms found to produce the compound may act as opportunistic pathogens. Here, we report the isolation and characterization of violacein from a non-pathogenic Antarctic Iodobacter strain. Its anti-microbial properties were also tested. The method proposed here for the purification of violacein shows high yields, indicating that this Antarctic microorganism could be a valuable source for this important pigment. This is the first characterization of violacein from an Antarctic Iodobacter strain and here we also present a viable method to obtain this pigment for potential biotechnological applications.

Ecological and efficient alternatives to industrial processes have sparked interest for using microorganisms and enzymes as biocatalysts. One of the difficulties is finding candidates capable of resisting the harsh conditions in which industrial processes usually take place. Extremophiles, microorganisms naturally found in "extreme" ecological niches, produce robust enzymes for bioprocesses and product development. Thermophiles like Geobacillus, Alyciclobacillus, Anoxybacillus, Pyrococcus and Thermoccocus are some of the extremophiles containing enzymes showing special promise for biocatalysis. Glutamate dehydrogenase used in food processes, laccases and xylanases in pulp and paper processes, nitrilases and transaminases for pharmaceutical drug synthesis and lipases present in detergents, are examples of the increasing use of enzymes for biocatalytic synthesis from thermophilic microorganisms. Some of these enzymes from thermophiles have been expressed as recombinant enzymes and are already in the market. Here we will review recent discoveries of thermophilic enzymes and their current and potential applications in industry.

A recombinant laccase from thermophilic bacteria was used to construct an enzyme–multi-walled carbon nanotube composite catalyst, which shows improved stability as a bio-electrocatalyst for the oxygen reduction reaction compared to similar conjugates prepared using the commercially available T. versicolor laccase.

This article reports the electrochemical studies of bio-electrocatalytic oxygen reduction reaction catalyzed by a new laccase from a thermophilic bacterium, which exhibits superior stability and activity retention compared to fungal laccases. The electro-kinetic study of this catalytic reaction was conducted using a classic tool of electrochemistry, the rotating ring disk electrode (RRDE). Bacillus sp. FNT laccase was immobilized onto a multiwall carbon nanotube modified glassy carbon disk electrode using a molecular tethering agent, 1-pyrenebutanoic acid succinimidyl ester (PBSE). The conditions for laccase immobilization were optimized to prepare a highly active bioconjugate for the electrochemical reduction of oxygen. The kinetic parameters such as Tafel slopes, number of electrons transferred, electrochemical rate constant and the electron transfer rate were calculated from RRDE measurements. The rate constant of the four-electron transfer reaction was calculated to be 3.21 x 10(-1) +/- 8.5 x 10(-3) cm s(-1). The slope value obtained from Tafel plot was close to that of value for the ideal four-electron transfer oxygen reduction, suggesting excellent electro-catalytic activity of the FNT laccase-MWCNT conjugates. (C) 2018 The Electrochemical Society.

Common alloys used for the manufacture of aircrafts are subject to different forms of environmental deterioration. A major one is corrosion, and there is a strong body of evidence suggesting that environmental microorganisms initiate and accelerate it. The development of an appropriate strategy to reduce this process depends on the knowledge concerning the factors involved in corrosion. In this work, a biofilm forming bacterial consortium was extracted in situ from the corrosion products formed in an aircraft exposed to Antarctic media. Two thermophilic bacteria, an Anoxybacillus and a Staphylococcus strain, were successfully isolated from this consortium. Two extracellular enzymes previously speculated to participate in corrosion, catalase and peroxidase, were detected in the extracellular fraction of the consortium. Additionally, we assessed the individual contribution of those thermophilic microorganisms on the corrosion process of 7075-T6 aluminum alloy, which is widely used in aeronautical industry, through electrochemical methods and surface analysis techniques.

Amine-transaminases (ATAs) are enzymes that catalyze the reversible transfer of an amino group between primary amines and carbonyl compounds. They have been widely studied in the last decades for their application in stereoselective synthesis of chiral amines, which are one of the most valuable building blocks in pharmaceuticals manufacturing. Their excellent enantioselectivity, use of low-cost substrates and no need for external cofactors has turned these enzymes into a promising alternative to the chemical synthesis of chiral amines. Nevertheless, its application at industrial scale remains limited mainly because most of the available ATAs are scarcely tolerant to harsh reaction conditions such as high temperatures and presence of organic solvents. In this work, a novel (S)-ATA was discovered in a thermophilic bacterium, Albidovulum sp. SLM16, isolated from a geothermal Antarctic environmental sample, more specifically from a shoreline fumarole in Deception Island. The transaminase-coding gene was identified in the genome of the microorganism, cloned and overexpressed in Escherichia coli for biochemical characterization. The activity of the recombinant ATA was optimal at 65 °C and pH 9.5. Molecular mass estimates suggest a 75 kDa homodimeric structure. The enzyme turned out to be highly thermostable, maintaining 80% of its specific activity after 5 days of incubation at 50 °C. These results indicate that ATA_SLM16 is an excellent candidate for potential applications in biocatalytic synthesis. To the best of our knowledge, this would be the first report of the characterization of a thermostable (S)-ATA discovered by means of in vivo screening of thermophilic microorganisms.