Low-resolution molecular shape, biochemical characterization and emulsification properties of a halotolerant esterase from Bacillus licheniformis.

Bacterial esterases are highly versatile enzymes, currently widely used in detergents, biosurfactants, bioemulsifiers and as biocatalysts in paper and food industries. Present work describes heterologous expression, purification, and biophysical and biochemical characterization of a halotolerant esterase from Bacillus licheniformis (BlEstA). BlEstA preferentially cleaves pNP-octanoate and both activity and stability of the enzyme increased in the presence of 2 M NaCl, and also with several organic solvents (ethanol, methanol and DMSO). Furthermore, BlEstA has considerable emulsifying properties, particularly with olive oil as substrate. Our studies also show that the enzyme is monomeric in solution and its small-angle X-ray scattering low-resolution molecular envelope fits well its high-resolution homology model.

GH43 endo-arabinanase from Bacillus licheniformis: Structure, activity and unexpected synergistic effect on cellulose enzymatic hydrolysis.

The hydrolysis of the plant biomass provides many interesting opportunities for the generation of building blocks for the green chemistry industrial applications. An important progress has been made for the hydrolysis of the cellulosic component of the biomass while, for the hemicellulosic components, the advances are less straightforward. Here, we describe the cloning, expression and biochemical and structural characterization of BlAbn1, a GH43 arabinanase from Bacillus licheniformis. This enzyme is selective for linear arabinan and efficiently hydrolyzes this substrate, with a specific activity of 127 U/mg. The enzyme has optimal conditions for activity at pH 8.0 and 45 °C and its activity is only partially dependent of a bound calcium ion since 70% of the maximal activity is preserved even when 1 mM EDTA is added to the reaction medium. BlAbn1 crystal structure revealed a typical GH43 fold and narrow active site, which explains the selectivity for linear substrates. Unexpectedly, the enzyme showed a synergic effect with the commercial cocktail Accellerase 1500 on cellulose hydrolysis. Scanning Electron Microscopy, Solid-State NMR and relaxometry data indicate that the enzyme weakens the interaction between cellulose fibers in filter paper, thus providing an increased access to the cellulases of the cocktail.