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Genetic Engineering & Biotechnology News | GENengnews.com | SEPTEMBER 1, 2016 | 29 Results As shown in Figure 2, the k L a increases with higher shaking rates. Af- higher a increases with higher shaking rates. Af- shaking rates. Af- ter a critical point (at higher shaking rates, e.g., ~200 rpm for rates, e.g., ~200 rpm for a shaking amplitude of 25 mm), the effect reverses. Regard- he a shaking amplitude of 25 mm), the effect reverses. Regard- effect reverses. Regard- ing process design, the determination of a suitable parameter on ing process design, the determination of a suitable parameter of a suitable parameter combination is key to optimal cultivation results, especially tivation combination is key to optimal cultivation results, especially results, especially if the cell growth is limited due to a high oxygen demand. to if the cell growth is limited due to a high oxygen demand. a high oxygen demand. Hence, the process parameters (e.g., aeration) have to rs Hence, the process parameters (e.g., aeration) have to (e.g., aeration) have to be adapted to the specific needs. o be adapted to the specific needs. the specific needs. Shaking at low rates (e.g., ng Shaking at low rates (e.g., at low rates (e.g., 80–160 rpm) and high filling vol- rpm) and high filling vol- umes only ensures kLa values be- ly ensures kLa values be- low 5h -1 1 -1 . In addition, increas- ing viscosity decreases the k osity ing viscosity decreases the k decreases the k L a value (Figure 2, A–D). Higher Figure value (Figure 2, A–D). Higher 2, A–D). Higher k L a values (between 50 and 60h es a values (between 50 and 60h (between 50 and 60h -1 ) were achieved (Figure 2) with low ieved were achieved (Figure 2) with low (Figure 2) with low filling volumes (1.2 –1.6 L) and lumes filling volumes (1.2 –1.6 L) and (1.2 –1.6 L) and medium to high shaking rates m medium to high shaking rates to high shaking rates (140–240 rpm). To estimate –240 (140–240 rpm). To estimate rpm). To estimate the k k L a value at different pa- rameters, Equation 1 could meters, rameters, Equation 1 could Equation 1 could be used in combination e be used in combination used in combination with with the values in Table 1. the values in Table 1. k L a = 10 ( C + n ∙ C n + V ∙ C V + C M C ∙ C C M C + n 2 ∙ C n n + n ∙ V ∙ C n V ) Summary The Thomson Optimum Growth shake flasks are geometrically modified and easy- to-operate cultivation systems. It was shown that very low shaking rates, high filling volumes, and high viscosities lead to k L a values lower than 5h -1 . Average shaking rates and filling volumes are sufficient to reach high cell densities in Newtonian culture broths as this is the case for mammalian cell expansions. When growing cells in non-Newtonian, high viscous culture broths, the resulting k L a values below 5h -1 may inhibit cell growth. Nevertheless, k L a values in the range of 50–60h -1 are possible, using high shaking rates (> 160 rpm) and low filling volumes (1.2 L). However, at higher shaking rates the shear stress may become a further limiting factor. Using Equation 1, the k L a value can be approximated and assists researchers to avoid oxygen transfer limitations as well as to optimize the cultivation process. BIOPROCESSING Tutorial Figure 2. The k L a value (from low (blue) to high (red)) at various shaking rates and filling volumes using the 5 L Thomson Optimum Growth flask, a shaking diameter of 25 mm, and different CMC concentrations (A: 0 g L -1 ; B: 4 g L -1 ; C: 8 g L -1 ; and D: 20 g L -1 ). Figure 1. Thomson shake flasks on the PreSens Shake Flask Reader with the custom-built metal plate and specially shaped clamps. Table 1. Terms and constants for the calculation of the k L a value of the 5 L flask with a shaking diameter of 25 or 50 mm. Table 1. Terms and Constants Term Constant Value 25 mm Value 50 mm Constant C 1.20999 0.241146 Shaking Rate n C n 0.015779 0.0328613 Filling Volume V C V -1.12218 -1.01553 CMC CMC C CMC -0.0169154 -0.0125852 (Shaking Rate) 2 n 2 C nn -0.0000547 -0.0001595 Shaking ∙ Filling n ∙ V C nV 0.0041648 0.0055152 Applicable in the Range 80–250 rpm 60–150 rpm Coefficient of Determination R 2 0.864 0.972 For a copy of our catalog or more information on the P ip et-A id XP 2 visit drummondsci.com. From the Developers of the Original Pipet-Aid ® Comfort T h e most comfortab le p ip ettor you ever laid a h an d on Co n ven i en ce U n in terrupted exten d ed operation Co n tro l Q u iet p recision p u mp resp on d s in stan tly to th e tou ch of th e b u tton D r u mmon d Pipet-A id s h ave set the standard for makin g pipetting in the lab oratory safer, easier, an d more con ven ien t. T he Pipet-A id ® X P 2 d elivers more. More comfort…more convenience…better control. 500 Parkway, Box 700 B roomall, PA 19008 M A D E IN US A Advanced Ergonomics for Working on a Bench Pipet-Aid ® XP 2 Pipet-Aid ® XP 2 Advanced Ergonomics for Working on a Bench ASCB Booth #919 and SFN Booth #2932