Response surface methodology optimization of partitioning of xylanase form Aspergillus Niger by metal affinity polymer-salt aqueous two-phase systems.

ABSTRACT

Aqueous two phase affinity partitioning system using metal ligands was applied for partitioning and purification of xylanase produced by Aspergillus Niger. To minimization the number of experiments for the design parameters and develop predictive models for optimization of the purification process, response surface methodology (RSM) with a face-centered central composite design (CCF) has been used. Polyethylene glycol (PEG) 6000 was activated using epichlorohydrin, covalently linked to iminodiacetic acid (IDA), and the specific metal ligand Cu was attached to the polyethylene glycol-iminodiacetic acid (PEG-IDA). The influence of some experimental variables such as PEG (10-18%w/w), sodium sulfate (8-12%), PEG-IDA-Cu2+ concentration (0-50% w/w of total PEG), pH of system (4-8) and crude enzyme loading (6-18%w/w) on xylanase and total protein partitioning coefficient, enzyme yield and enzyme specific activity were systematically evaluated. Two optimal point with high enzyme partitioning factor 10.97 and yield 79.95 (including 10% PEG, 12% Na2SO4, 50% ligand, pH 8 and 6% crude enzyme loading) and high specific activity in top phase 42.21 (including 14.73% PEG, 8.02% Na2SO4, 28.43% ligand, pH 7.7 and 6.08% crude enzyme loading) were attained. The adequacy of the RSM models was verified by a good agreement between experimental and predicted results.