Urea removal in rosé and red wines by immobilised acid urease in a packed bed reactor

Abstract

The aim of this work was to develop and study the performance of a packed bed immobilized enzyme reactor for the effective removal of urea in high polyphenol wines. Purified acid urease from Lactobacillus fermentum was immobilized on Eupergit® C 250 L yielding a biocatalyst with enzyme loading and specific activity per g of dry support of 109.7 ± 2.4 mg and 677 ± 39 IU, respectively. Incubation of the developed biocatalyst at 20 °C in rosé and red wines resulted in a two-phase deactivation mechanism, with a residual asymptotic activity after about 170 h of 67% and 24%, respectively. The developed biocatalyst was used in a packed bed reactor with recycling to efficiently remove urea from rosé and red wines. A model for the bioreactor allowed to estimate the apparent pseudo-first order kinetic constant for urea hydrolysis, which for three repeated bioconversion cycles varied in the range 2.8–4.1 cm3 g−1 min−1 for the rosé wine and 1.1–2.7 cm3 g−1 min−1 for the red wine. Results of repeated bioconversion cycles allowed to conclude that enzyme deactivation by phenols is the main reason for the low urease activity observed in high polyphenol wines. This suggested the use of immobilization as a means to overcome the present limitations in the use of the free enzyme.