CONTINUOUS MONITORING OF ETHANOL FOR BIOPROCESS CONTROL BY A CHEMICALSENSOR

This paper describes the first example of continuous process monitorin g by a typical chemical sensor. An alcohol-selective optical sensor, b ased on a solvent polymeric membrane, is applied to continuous monitor ing of ethanol produced in a bioreactor. The membrane-incorporated chr omophore and ligand, ETH 6022, shows an absorption band at 305 nm wave length. The sensing principle relies on the base-catalyzed formation o f the hemiacetal with ethanol, leading to a hypsochromic shift in the absorption spectrum. Monitoring of ethanol is performed in the vapour phase of the reactor medium without any sample pre-treatment and using the same sensing device for several days. At the same rime, for compa rative purposes, the ethanol concentration in the liquid phase is dete rmined using the reference method of distillation followed by refracto metric density measurement. The selectivity pattern of the sensor with respect to other volatile alcohols in the vapour phase is discussed.