P1: Automated online control of bacteria fermentation to detect the cell growth with an optical density measuring sensor

Monday, November 7, 2011
Capri Ballroom (Marriott Marco Island)
Diego Bochoeyer Sr.1, Maria Florencia Perez Lippi2, Maximiliano Dxalessio3, Gustavo Stasiejko4, Diego Petruzzi1 and Gabriel Gutkind1, (1)Fermentation, Novozymes BioAg, Buenos Aires, Argentina, (2)Marketing, Endress + Hausser, Buenos Aires, Argentina, (3)Development & Process Support, Novozymes BioAg, Milwaukee, MN, (4)Sales, Endress + Hausser, Buenos Aires, Argentina
The goal of this work was to validate the use of an Endress Hauser (E+H) optical density (OD) online sensor for nitrogen fixing bacteria in large-scale fermentation processes. The main motivation was to collect online data during the fermentation process in order to make quick and better decisions. The advantage of using this type of device is minimizing the need for reiterative sampling and online process quality control.
In a 5000 lt stainless steel fermentor two 880 nm sensors (5 mm and 10 mm optical path) were installed and tested. Standard procedures were used to scale up and grow the cells. Samples were taken every two hours and OD was measured at 540 and 880 nm in a Thermo Genesys 20 spectrophotometer. In parallel, we registered the value measured by the optical sensors installed in the fermentor.
The results indicated that there were no differences between both optical path sensors (5 mm and 10 mm). Plotted regression analysis between offline 540 nm OD versus online 880 nm OD showed no differences for all strains analyzed. Moreover, when viable cells’ measurements were compared between the two methods, an analogous behavior was observed. High standard deviation values were found due to high variability among lots. However, the degree OD increases in both method was the same.
This work demonstrates that the online E+H sensor can be used for OD measurement in large-scale fermentation processes. Furthermore, real time tracing of the cells allows making better decisions at early-stage during the process.
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