New miniature on-line optical cell biomass probe with wide linear range and bubble discrimination

Immersible on-line cell biomass probes have historically suffered from a limited range of linear response to biomass and sensitivity to process variables, such as agitation and gas sparge rate.  A new optical probe has been developed that provides linear response over 4 orders of magnitude of biomass (e.g. 0.01-200 g/L yeast dry cell weight).  The small probe diameter (e.g. 3 mm) and minimal optical penetration depth (e.g. <3 cm) make it suitable for a wide range of vessel types, including miniature bioreactors (e.g. 250 mL).  Interference from bubbles is largely eliminated through a novel measurement technique, making the results nearly insensitive to agitation and sparge rate changes.  Example results will be presented for cultures of Saccharomyces cerevisiae and e. coli.