Mycelium-bound chlorogenate hydrolase of Aspergillus niger AKU 3302 as a stable immobilized biocatalyst

Abstract

CHase catalyzes chlorogenic acid (CGA) hydrolysis to yield equimolar quinic (QA) and caffeic (CA) acids, products of high value and keen industrial interest. We proposed the preparation and characterization of the nonviable mycelium of Aspergillus niger AKU 3302 containing a cell-associated CHase (CHase biocatalyst) for application in hydrolyzing the CGA from yerba mate residues to produce QA and CA. When the vegetative mycelium was heated at 55 °C for 30 min, no loss of CHase activity occurred, but vegetative mycelial growth and spore germination ended. The CHase biocatalyst did not limit mass transfer above 100 strokes min^-1. The reaction rate increased with catalyst loading and was kinetically controlled. The CHase biocatalyst exhibited suitable biochemical properties (optimum pH 6.5 at 50 °C) and high thermal stability (remaining stable at up to 50 °C for 8 h). The cations in yerba mate extracts did not affect CHase activity. We observed no apparent loss in the activity of the CHase biocatalyst after even 11 batch cycles of continuous use. The biocatalyst retained 85% of its initial activity after 25 days of storage at pH 6.5 and 5 °C. When a yerba mate extract was passed through a glass column packed with the biocatalyst, an effective bioconversion of CGA into CA and QA occurred. CHase activity produced a natural biocatalysis with considerable operational and storage stability; which capability, being a novel biotechnological process, can be used in the bioconversion of CGA from yerba mate residues into CA and QA at a substantially reduced cost.

Keywords: Aspergillus niger; Chlorogenic acid hydrolysis; Mycelium-bound chlorogenate hydrolase; Whole-cells; Year mate (llex paraguariensis).