Extraction of lipase from Aspergillus niger by insoluble complex formation with anionic and cationic polyelectrolytes

Abstract

The insoluble complex formation between lipase from Aspergillus niger and the electrically charged polymers, polyacrylic acid (PAA), poly-vinil sulfonate (PVS) and chitosan (CHI), was studied by using turbidimetric and enzymatic methods on a commercial lyophilized (Ly) and a filtrate of solid culture medium (SCM). It could be shown that both electrostatic interactions as hydrophobic are involved in the formation of insoluble complexes. The kinetics of the complex formation were determined. Lipase enzymatic activity is maintained through time in the presence of polyelectrolytes. On the Ly the three polymers produced insoluble complex, with a stoichiometric ratio (polymer mass per mass of Ly from Aspergillus niger) of PAA/Ly: 0.035, PVS/Ly: 0.099 and CHI/Ly: 0.071 mg/mg Ly. For the anionic polyelectrolytes, the PAA presents slightly better results than PVS to be used when the protein concentration is similar to the lyophilized. The filtrate of the SCM has a total protein concentration much lower than commercial lyophilized. Working with CHI as cationic polymer a recovery of the activity in the re-dissolved precipitate higher than 80%, with purification factors greater than 3 were achieved, both at 8 and 20 ◦C. Therefore, this methodology could be used as a first step of purification.