Shelby R. Anderson’s research while affiliated with Georgia Institute of Technology and other places

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Publications (3)


Sparged but not stirred: Rapid, ADH-NADH oxidase catalyzed deracemization of alcohols in a bubble column
  • Article

December 2020

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35 Reads

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19 Citations

Chemical Engineering Journal

Shelby R. Anderson

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John M. Woodley

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We investigate in detail both the deracemization reaction rate and maximum conversion of (R,S)-1-phenylethanol in a bubble column and the deactivation rates of both enzymes involved, alcohol dehydrogenase (ADH) and NADH oxidase (nox2). Instead of the predicted ellipsoidal shape of the bubbles, we observe a spherical shape in all our experiments. Calculated values for the area-specific mass transfer coefficient kLa in sparged, but not stirred, solution ranged from 17 to 87 h⁻¹. We find that minimizing the air–liquid interface over time results in the lowest rate of nox2 deactivation. The onset of nox2 dissociation beyond the initial 50 h correlates with a tenfold increase in the observed deactivation rate constant. The highest conversion (99%) for deracemizing 50 mM (R,S)-1-phenylethanol was reached in the shortest reaction time (6 h) if large air bubbles (diameter 2.6 mm) at slow flowrates (5 bubbles/s) were employed. A faster flowrate, which delivers more oxygen per unit time, increased the initial reaction rate but resulted in a slower rate at higher conversions and ultimately incomplete maximum conversion (94%). Reaction rates under sparging were 4–8 times faster than in quiescent solution. Lastly, stirring did not significantly aid conversion (41% vs 37% in quiescent solution after 12 h) but caused increased enzyme deactivation (44 h vs 136 h half-life quiescent solution).


Oxygen Transfer vs. Enzyme Stability

May 2019

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104 Reads

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Shelby R. Anderson

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The inside cover picture, provided by Andreas Bommarius, John Woodley, and co‐workers, illustrates how oxygen transfer into an enzyme‐containing solution and enzyme stability are often at odds with each other. A vigorously sparged and stirred tank is best for oxygen transfer but worst for enzyme stability, while a quiescent solution shows the opposite behavior: best for stability but worst for transfer of molecular oxygen. A bubble column, the focus of the work described in this contribution, allows good oxygen transfer but mostly preserves enzyme stability. Details can be found in the full paper on pages XXXX–XXXX (M. Dias Gomes, B. R. Bommarius, S. R. Anderson, B. D. Feske, J. M. Woodley, A. S. Bommarius, Adv. Synth. Catal. 2019, 361, XXXX–XXXX; DOI:10.1002/adsc.201900213).


Diagram of the bubble column setup. Inset: image of bubbles during representative experiments.
Residual activity of NOX as a function of time.
A Deactivation of NOX in the presence of either (R) or (S)‐ADH during conversion of 1‐phenylethanol. B Corresponding HPLC analysis of consumed (R,S)‐1‐phenylethanol. C Deactivation of NOX in the presence of both (R) and (S)‐ADH during conversion of 1‐phenylethanol. D Corresponding HPLC analysis of consumed 1‐phenylethanol. All experiments were performed with sparged air. All measurements for the experiments were done in duplicates with a standard deviation of 1.5%. The experiment with both ADH in C,D was repeated twice with similar results within the time frame of 6 hours.
Enzymatic oxidation of racemic 1‐phenylethanol using a coupled ADH/NOX system.
Bubble Column Enables Higher Reaction Rate for Deracemization of (R,S)‐1‐Phenylethanol with Coupled Alcohol Dehydrogenase/NADH Oxidase System
  • Article
  • Publisher preview available

April 2019

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67 Reads

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28 Citations

One of the major drawbacks for many biocatalysts is their poor stability under industrial process conditions. A particularly interesting example is the supply of oxygen to biooxidation reactions, catalyzed by oxidases, oxygenases or alcohol dehydrogenases coupled with NAD(P)H (reduced nicotinamide adenine dinucleotide phosphate) oxidases, which all require the continuous supply of molecular oxygen as an oxidant or electron acceptor. Commonly, oxygen is supplied to the bioreactor by air sparging. To ensure sufficient oxygen transfer from the gas to the liquid phase, stirring is essential to disperse the gas bubbles and create high gas‐liquid interfacial area. Studies indicate that the presence of gas‐liquid interface induces enzyme deactivation by protein unfolding which then readily aggregates and can subsequently precipitate. This contribution has examined the effects of stirring and the presence of gas‐liquid interface on the kinetic stability of water‐forming NAD(P)H oxidase (NOX) (EC1.6.3.2). These effects were studied separately and a bubble column apparatus was successfully employed to investigate the influence of gas‐liquid interfaces on enzyme stability. Results showed that NOX deactivation increases in proportion to the gas‐liquid interfacial area. While air enhances the rate of stability loss compared to nitrogen, stirring causes faster loss of activity in comparison to a bubble column. Finally, deracemization of 1‐phenylethanol, using a coupled alcohol dehydrogenase /NADH oxidase system (ADH/NOX), proceeded with a higher rate in the bubble column than in quiescent or in a stirred solution, although, inactivation was also accelerated in the bubble column over a quiescent solution. image

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Citations (2)


... With free MeFDH1, formate rapidly reached 0.64 M at − 0.164 V within 96 h; however, no further increase was observed thereafter (Fig. 3b). This was supposedly attributed to the denaturation of free MeFDH1 by shear stress caused by CO 2 bubbling [51]. In contrast, the immobilized enzyme enabled a steady increase in formate concentration up to 1.74 M for at 216 hours. ...

Reference:

Enzymatic conversion of CO 2 to formate: The potential of tungsten-containing formate dehydrogenase in flow reactor system
Sparged but not stirred: Rapid, ADH-NADH oxidase catalyzed deracemization of alcohols in a bubble column
  • Citing Article
  • December 2020

Chemical Engineering Journal

... Bubble column reactors-such as those used in sparging and purging techniques-are operated by introducing gas into either a liquid phase or a liquid-solid suspension to create bubbles. Porous materials and diffusers are sometimes used to achieve uniform bubble sizes (Alam et al. 2023;Dias Gomes et al. 2019;Hayashi et al. 2015;Singh et al. 2019;Yasuoka et al. 2011). Bubble column reactors are versatile reactors that facilitate a diverse range of processes, including extraction (Nafi and Taseidifar 2024;Zhao et al. 2009) and chemical reactions (Alam et al. 2023;Hayashi et al. 2015;Singh et al. 2019;Yasuoka et al. 2011;Dias Gomes et al. 2019), among others. ...

Bubble Column Enables Higher Reaction Rate for Deracemization of (R,S)‐1‐Phenylethanol with Coupled Alcohol Dehydrogenase/NADH Oxidase System