Biooxidation of 2-phenylethanol to phenylacetic acid by whole-cell Gluconobacter oxydans biocatalyst immobilized in polyelectrolyte complex capsules

Abstract

A high-performance biocatalyst in the form of encapsulated cells of Gluconobacter oxydans have been developed for production of phenylacetic acid (PAA) as a natural flavor component. Polyelectrolyte complex (PEC) capsules consisting of sodium alginate, cellulose sulfate, poly(methylene-co-guanidine), CaCl₂, and NaCl were used for highly controlled and mild encapsulation of cells. Utilization of encapsulated G. oxydans cells was a significant improvement on existing data on operational stability of cells and cumulative product concentration during biocatalytic production of PAA from 2-phenylethanol. Concerning operational stability, encapsulated cells were active over 12 cycles with a high biotransformation rate, while free cells were inactive after 7 cycles of use. The biocatalytic properties of encapsulated G. oxydans were tested in a bubble column reactor over 7 days with a final cumulative product concentration of 25 g/L. High cell viability (90%) was observed within PEC capsules by confocal laser scanning microscopy, performed before and after repetitive PAA production in the bubble column reactor. The surface microstructure of fully hydrated capsules with and without G. oxydans cells was investigated and compared using an environmental scanning electron microscope.

Keywords::

• Gluconobacter oxydans
• natural flavors
• phenylacetic acid
• immobilized whole-cell biocatalyst
• polyelectrolyte complex capsules
• environmental scanning electron microscopy

Acknowledgement

This work was supported by the Slovak Grant Agency for Science VEGA 1/0229/12 and by the Slovak Research and Development Agency under contract No. APVV-0302-10 and 0282-11; and by Grant Agency of the Czech Republic GA14-22777S. This publication is the result of the project implementation: Applied research in the field of industrial biocatalysis, ITMS code: 26240220079 supported by the Research & Development Operational Programme funded by the ERDF.

Declaration of interest: The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.