Application of immersed silicone rubber membrane module for biocatalytic production of 2-phenylethanol and phenylacetic acid

Abstract

Abstract Natural phenylacetic acid can be produced by the biotransformation of 2-phenylethanol by bacterial strains, such as Gluconobacter oxydans, with incomplete oxidative metabolism. 2-Phenylethanol can be produced by the biotransformation from L -phenylalanine using ordinary yeasts such as Saccharomyces cerevisiae. Both compounds are valuable components in flavor industry, where the demand for substances of natural origin has been increasing in recent years and can be satisfied by microbial production. In this work, we proposed two membrane hybrid systems for extractive bioproduction of 2-phenylethanol consisting of a mechanically stirred tank bioreactor, immersed silicone rubber membrane module for product removal, and equipment for the regeneration of water extractant from the membrane module applying two approaches: 1. extract was led to a fixed bed adsorption column for 2-phenylethanol accumulation; 2. extract was led to an airlift bioreactor with the bacterial strain Gluconobacter oxydans, where 2-phenylethanol was oxidized to phenylacetic acid. Biotransformation experiments performed in the proposed hybrid systems proved its functionality and capability to overcome product inhibition and to provide the desired product in high purity. In second approach, phenylacetic acid, as a product of higher value, was produced directly from L -phenylalanine using two strains of microorganisms in a unique double bioreactor membrane hybrid system.