Difference between revisions of "Team:Calgary/PHB Fermentation"

Line 18: Line 18:
  
 
<h2> Overview </h2>
 
<h2> Overview </h2>
−
<p>In this stage of the process, engineered <i> E. coli</i> is fermented in a VFA-rich stream obtained in the previous step to produce PHB. This continuous fermentation process occurs in a 5L <b>stirred-tank bioreactor</b> at 37 degrees Celsius and under anaerobic conditions. A continuous flow of the VFA-rich stream is generated by the pump. To achieve continuous fermentation, a <b>mechanical self-cleaning filter</b> with 0.2-micron filters is used to separate and recycle bacteria back to the bioreactor. The resulting bacteria-free harvest stream that contains PHB is then passed to PHB extraction and water recovery. The proposed process is shown in Figure 1.</p>
+
<p>In this stage of the process, VFA-rich stream from the previous step is fermented by engineered <i> E. coli</i> to produce PHB. This continuous fermentation process occurs in a 5L stirred-tank bioreactor at 37°C and under anaerobic conditions. A continuous flow of the VFA-rich stream is generated by the pump. To achieve continuous fermentation, a mechanical self-cleaning filter with 0.2-micron filters is used to separate and recycle bacteria back to the bioreactor. The resulting bacteria-free harvest stream that contains PHB is then passed to PHB extraction and water recovery. The proposed process is shown in Figure 1.</p>
  
 
<p><center><img src="https://static.igem.org/mediawiki/2017/c/cf/Calgary2017_PHBFermentation.png" alt="PHB Fermentation" style="width:100%"></center></p>
 
<p><center><img src="https://static.igem.org/mediawiki/2017/c/cf/Calgary2017_PHBFermentation.png" alt="PHB Fermentation" style="width:100%"></center></p>
Line 28: Line 28:
 
<li> External membrane bioreactor (EMB) </li>
 
<li> External membrane bioreactor (EMB) </li>
 
<li> Immersed membrane bioreactor (IMB): specifically the hollow fiber and the flat sheet designs </li>
 
<li> Immersed membrane bioreactor (IMB): specifically the hollow fiber and the flat sheet designs </li>
−
<li> Stirred-tank bioreactor with acoustic cell separation </li>
 
 
<li> Stirred-tank bioreactor with self-cleaning filter separation </li>
 
<li> Stirred-tank bioreactor with self-cleaning filter separation </li>
 
</ul>
 
</ul>
 +
 
<p>The major disadvantage of membrane bioreactors is fouling. Because of fouling, frequent filter cleaning and filter replacement might be required resulting in higher crew-time requirements and transportation costs to supply replacement membranes.</p>
 
<p>The major disadvantage of membrane bioreactors is fouling. Because of fouling, frequent filter cleaning and filter replacement might be required resulting in higher crew-time requirements and transportation costs to supply replacement membranes.</p>
−
<p>After literature search on acoustic cell separation, we concluded that this option is not ideal for the scale of our process.</p>
+
 
 
<p>The stirred-tank bioreactor, on the other hand, provides continuous agitation and easy temperature control, while the implementation of the self-cleaning filter reduces fouling. With this in mind, the stirred-tank bioreactor combined with the self-cleaning filter was chosen as the optimal design for the process. The ESM analysis for the final PHB fermentation system is summarized in Table 1.</p>  
 
<p>The stirred-tank bioreactor, on the other hand, provides continuous agitation and easy temperature control, while the implementation of the self-cleaning filter reduces fouling. With this in mind, the stirred-tank bioreactor combined with the self-cleaning filter was chosen as the optimal design for the process. The ESM analysis for the final PHB fermentation system is summarized in Table 1.</p>  
  

Revision as of 01:48, 31 October 2017

Header

PHB Fermentation

Overview

In this stage of the process, VFA-rich stream from the previous step is fermented by engineered E. coli to produce PHB. This continuous fermentation process occurs in a 5L stirred-tank bioreactor at 37°C and under anaerobic conditions. A continuous flow of the VFA-rich stream is generated by the pump. To achieve continuous fermentation, a mechanical self-cleaning filter with 0.2-micron filters is used to separate and recycle bacteria back to the bioreactor. The resulting bacteria-free harvest stream that contains PHB is then passed to PHB extraction and water recovery. The proposed process is shown in Figure 1.

PHB Fermentation

Figure 1: Diagram of the proposed PHB fermentation process.

Design options considered

Other considered design options include:

  • External membrane bioreactor (EMB)
  • Immersed membrane bioreactor (IMB): specifically the hollow fiber and the flat sheet designs
  • Stirred-tank bioreactor with self-cleaning filter separation

The major disadvantage of membrane bioreactors is fouling. Because of fouling, frequent filter cleaning and filter replacement might be required resulting in higher crew-time requirements and transportation costs to supply replacement membranes.

The stirred-tank bioreactor, on the other hand, provides continuous agitation and easy temperature control, while the implementation of the self-cleaning filter reduces fouling. With this in mind, the stirred-tank bioreactor combined with the self-cleaning filter was chosen as the optimal design for the process. The ESM analysis for the final PHB fermentation system is summarized in Table 1.

Table 1: ESM analysis for the proposed PHB fermentation system.
Self-cleaning filter Stirred-tank bioreactor
Power (kW) 2 0.38
Weight (kg) 16 15
Volume (m^3) 0.028 0.1153
Spares & Consumables (kg/day) 0 0
Spares & Consumables (m^3) 0 0
ESM Estimation 196 73