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28 | SEPTEMBER 1, 2016 | GENengnews.com | Genetic Engineering & Biotechnology News Innovators in Optical Monitoring www.buglab.com Bubble Trouble? The Clear Solution is BugLab's proBE 3000 Biomass Sensor Featuring: Biomass Range from <0.01 to 200 g/L DCW with 1 Probe Linear response over more than 4 orders of magnitude Highly Effective Bubble Discrimination Accurate under severe growth conditions including high aeration and/or agitation Extra Slim Profile — 3 mm diameter Fits in most vessel sizes including 250 mL and smaller Jolanda Meister, Rüdiger W. Maschke, Sören Werner, Gernot T. John, Ph.D., and Dieter Eibl, Ph.D. In biotechnology, the use of shake flasks is widespread due to their easy handling, es- pecially in process design and optimization as well as in small-scale upstream processing and inoculum production. Recently, geometrically optimized Thomson Optimum Growth™ shake flasks were introduced to the market, promoting higher yields with the same shaker foot- print. Knowledge on different engineering parameters (including the oxygen mass transfer coefficient, the mixing time, or the power consumption) is essential to com- pare these new flasks with established shake flasks and to evaluate potential benefits. In the present work, the oxygen mass transfer in Thomson Optimum Growth dis- posable shake flasks is quantified at 500 mL and 5 L using the PreSens Shake Flask Reader. Erlenmeyer and Fernbach shake flasks are still the predominant shapes, despite their limitations (e.g. the relatively low filling vol- umes). Consequently, Thomson Instru- ments developed a new shake flask design: Optimum Growth for cell cultures, allow- ing filling volumes of up to 60% of the nominal volume. The Shake Flask Reader is built to mea- sure the dissolved oxygen concentration and the pH value in shake flasks by means of single-use sensor spots that are attached to the inner surface of the shake flask. Besides a reduced contamination risk, another decisive advantage of the sensor spots (compared to conventional oxygen probes) is their small size, which does not change the flow behav- ior. The device can accommodate and mea- sure up to nine shake flasks (from 125–2,000 mL) simultaneously. The data is transmitted to a PC via a Bluetooth connection. To attach the 5 L Thomson shake flask to the shake flask reader, a custom-built clamp and metal plate were used to reduce the large distance between the sensor in the flask and the reader (Figure 1). For the 500 mL flask, a standard clamp was used. To determine the k L a value, the dynamic gassing-out method was used (according to the recommendations of the DECHEMA single-use technology expert group). In this procedure, nitrogen was passed directly into the bulk solution via tubes until an oxygen concentration below 20% was attained. Sub- sequently, the headspace was purged with air. Afterwards, the lid was removed to focus on the oxygen transition from the gas to the liquid phase. Measurement was stopped at an oxygen concentration of 80%. The maxi- mum and minimum dissolved oxygen values were scaled. Subsequently, the y-axis values were calculated and plotted in the range of 20–80% as a function of time. A linear trend line was inserted and the k L a value calcu- lated. The experiments were performed with varying shaking speeds on two popular com- mercial shakers with the two most frequent- ly used shaking diameters of 25 mm and 50 mm and different filling volumes. All experi- ments were conducted in triplicate. Field of Application The Optimum Growth flasks are intended for cultivating cell cultures of plant and animal origin up to 3 L filling volumes. During culti- vation with plant cells, the viscosity increases due to high cell concentration and aggrega- tion. Carboxymethylcellulose sodium salt (CMC) was used to simulate several viscosities (aqueous solutions of 4, 8, and 20 g L -1 ). These concentrations correlate well with packed cell volumes (PCV) at different stag- es of plant cell cultivation. The viscosity of plant cell suspensions may reach values of 0.4 Pa s (equivalent to 70% PCV of a Nico- tiana tabacum Bright-Yellow 2 cell suspen- sion or 20 g L -1 CMC solution) and show shear thinning behavior. Culture Broth Viscosity Evaluated in Shake Flasks Studies How to Efficiently Shake Viscous Culture Broths BIOPROCESSING Jolanda Meister, Rüdiger W. Maschke, Sören Werner, and Prof. Dieter Eibl are with the Zurich University of Applied Sciences, School of Life Sciences and Facil- ity Management, Institute of Chemistry and Biotechnology, and Dr. Gernot T. John (g.john@presens.de) is with PreSens Precision Sensing. Website: www.presens.de. Tutorial