Bacterial Laccases: Some Recent Advances and Applications

Laccases belong to the large family of multi-copper oxidases (MCOs) that
couple the one-electron oxidation of substrates with the four-electron reduction of
molecular oxygen to water. Because of their high relative non-specific oxidation
capacity particularly on phenols and aromatic amines as well as the lack of requirement
for expensive organic cofactors, they have found application in a large number
of biotechnological fields. The vast majority of studies and applications were
performed using fungal laccases, but bacterial laccases show interesting properties
such as optimal temperature above 50 C, optimal pH at the neutral to alkaline range,
thermal and chemical stability and increased salt tolerance. Additionally, bacterial
systems benefit from a wide range of molecular biology tools that facilitates their engineering and achievement of high yields of protein production and set-up of costeffective
bioprocesses. In this review we will provide up-to-date information on the
distribution and putative physiological role of bacterial laccases and highlight their
distinctive structural and biochemical properties, discuss the key role of copper in
the biochemical properties, discuss thermostability determinants and, finally, review
biotechnological applications with a focus on catalytic mechanisms on phenolics and
aromatic amines.