A FIBEROPTIC CARBON-DIOXIDE SENSOR FOR FERMENTATION MONITORING

We have developed a fiber-optic chemical sensor for determining dissol ved carbon dioxide and assessed its performance for the on-line monito ring of fermentation, The sensor operates on the Severinghaus pCO(2) e lectrode principle it consists of a pH sensitive dye (hydroxypyrenetri sulfonic acid, HPTS) in an HCO3- buffer solution entrapped in an expan ded PTFE support held at the distal end of an optical fiber by a gas p ermeable membrane, CO2 crossing the membrane produces a pH change in t he indicator solution. This change is related to the external CO2 conc entration by the Henderson-Hasselbach equation. The sensor has a rever sible working dissolved CO2 dynamic range of 0-0.25 atm, The sensor ca n be autoclaved without affecting its calibration. Results are present ed for the on-line determination of CO2 production in beer fermentatio n.