Evaluation of a new turbidimeter design incorporating a microprocessor-controlled variable pathlength cuvette.

A microprocessor-controlled, variable pathlength turbidimeter was designed, constructed, and its operation verified and accuracy determined using formazin as a turbidity standard. The turbidimeter was also characterized with the fermentation broths of Saccharomyces cerevisiae and Escherichia coli. The range of turbidities quantified using the instrument spanned from 70 to 1,000 Nephlometric Turbidity Units, with a measurement accuracy between 2% and 11% of the instrument's full-scale reading. The precision of the instrument was determined to be 0.077%. The turbidimeter was used to continuously monitor the biomass concentration of an Escherichia coli fermentation and provided instantaneous concentration estimates which corresponded with gravimetrically determined biomass concentrations to within 12%.