title: An Innovative Optical Sensor for the Online Monitoring and Control of Biomass Concentration in a Membrane Bioreactor System for Lactic Acid Production.
abstract: Accurate real-time process control is necessary to increase process efficiency, and optical sensors offer a competitive solution because they provide diverse system information in a noninvasive manner. We used an innovative scattered light sensor for the online monitoring of biomass during lactic acid production in a membrane bioreactor system because biomass determines productivity in this type of process. The upper limit of the measurement range in fermentation broth containing Bacillus coagulans was ~2.2 g·L(-1). The specific cell growth rate (µ) during the exponential phase was calculated using data representing the linear range (cell density ≤ 0.5 g·L(-1)). The results were consistently and reproducibly more accurate than offline measurements of optical density and cell dry weight, because more data were gathered in real-time over a shorter duration. Furthermore, µ(max) was measured under different filtration conditions (transmembrane pressure 0.3-1.2 bar, crossflow velocity 0.5-1.5 m·s(-1)), showing that energy input had no significant impact on cell growth. Cell density was monitored using the sensor during filtration and was maintained at a constant level by feeding with glucose according to the fermentation kinetics. Our novel sensor is therefore suitable for integration into control strategies for continuous fermentation in membrane bioreactor systems.
authors.affiliation: Institute of Bioprocess Engineering and Membrane Technology, University of Applied Sciences Mittelhessen, Wiesenstr. 14, 35390 Giessen, Germany. rong.fan@lse.thm.de.
authors.forename: Rong
authors.initials: R
authors.lastname: Fan
authors.affiliation: Institute of Bioprocess Engineering and Membrane Technology, University of Applied Sciences Mittelhessen, Wiesenstr. 14, 35390 Giessen, Germany. mehrdad.ebrahimi@lse.thm.de.
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Ebrahimi
authors.affiliation: Institute of Bioprocess Engineering and Membrane Technology, University of Applied Sciences Mittelhessen, Wiesenstr. 14, 35390 Giessen, Germany. Hendrich.quitmann@ime.fraunhofer.de.
authors.forename: Hendrich
authors.initials: H
authors.lastname: Quitmann
authors.affiliation: FAUDI Aviation GmbH, Scharnhorststr. 7B, 35260 Stadtallendorf, Germany. m.aden@faudi-aviation.com.
authors.forename: Matthias
authors.initials: M
authors.lastname: Aden
authors.affiliation: Institute of Bioprocess Engineering and Membrane Technology, University of Applied Sciences Mittelhessen, Wiesenstr. 14, 35390 Giessen, Germany. peter.czermak@lse.thm.de.|Department of Chemical Engineering, Kansas State University, 1005 Durland Hall, Manhattan, KS 66506, USA. peter.czermak@lse.thm.de.|Faculty of Biology and Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen, Germany. peter.czermak@lse.thm.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Czermak
mesh_terms: D018533:Biomass; D019149:Bioreactors; D015374:Biosensing Techniques / Q000379:methods*; D005285:Fermentation; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry / Q000302:isolation & purification*; D008566:Membranes / Q000737:chemistry; D055095:Optics and Photonics
chemical_list: D019344:Lactic Acid
keywords: biomass measurement; lactic acid production; membrane filtration; online monitoring; optical sensor