My research aimed to evaluate the efficiency of hollow-fiber membrane and the continuous liquid-liquid extraction of medium-chain fatty acid from fermentation broth. I seek to understand how this membrane differs from traditional techniques by optimizing the extraction process and determination of the scalability of this method for industrial use. Current experimental challenge include inefficient extraction of medium-chain fatty acid from fermentation broth, which often lead to the inhibition of the chain-elongation microbes.
Traditional techniques often face issues like batch-processing limitation, high energy consumption, and high solvent usage. Our protocol offers several advantages over traditional techniques. These include high selectivity and efficiency in extracting the medium-chain fatty acids from fermentation broths which leads to reduced solvent usage and continuous operation from batch processing.
Additionally, this method can easily be replicated for diverse applications. To begin, prepare the organic phase extraction solution and reservoir by adding the extraction solution to a two liter glass reservoir and placing it on a magnetic stir plate. Next, position a 100 RPM variable speed pump drive with a polytetrafluoroethylene diaphragm pump head next to the reservoir.
Using flexible pump tubing, connect the outflow port of the extraction solution reservoir to the diaphragm pump inlet. Then connect the pump outlet to the shell-side inlet at the base of the forward extraction membrane. Now, connect the shell-side outlet at the top of the forward extraction membrane to the shell-side inlet located at the base of the backward extraction membrane.
Then connect the shell-side outlet at the top of the backward extraction membrane to the return port on the extraction solution reservoir. To prepare the aqueous phase stripping solution and reservoir, pour the solution into a four liter glass reservoir with a magnetic stir bar and place it on a magnetic stir plate. Integrate a pH control system with a set point of pH nine with the stripping solution reservoir.
Insert the pH probe through the stripping solution reservoir port and suspend it in the stripping solution. To install the hollow-fiber membrane filter, place a 300 RPM variable speed pump drive adjacent to the bioreactor. Affix the hydrophilic hollow-fiber membrane to a ring stand above the peristaltic pump.
Stack two peristaltic pump heads, large and small, on the pump drive. Now, using flexible tubing, connect the outflow port at the bioreactor to the large pump head inlet. Then connect the large pump head outlet to the hydrophilic hollow-fiber membrane filter at the tube side inlet located at the base of the filter.
Cap the top shell-side port of the filter to prevent the influx of air. To connect the forward extraction membrane, affix the first hydrophobic hollow-fiber membrane module to a ring stand above the pump. Using flexible pump tubing, connect the hydrophilic hollow-fiber membrane filter at the shell-side outlet to the small pump head inlet.
Then connect the small pump head outlet to the forward extraction membrane at the tube side inlet located at the base of the module. Now using a coupling fitting and tee-fitting, connect the pressure gauge and flow-restriction valve to the tube side outlet of the forward extraction membrane. Next, connect the tube side outlet of the forward extraction membrane to the return port at the bioreactor.
To connect the backward extraction membrane, place a 300 RPM variable speed pump drive adjacent to the bioreactor. Affix the second hydrophobic hollow-fiber membrane module to a ring stand above the peristaltic pump. Then using flexible pump tubing, connect the stripping solution reservoir outflow port to the peristaltic pump inlet and the pump outlet to the tube side inlet at the base of the backward extraction membrane.
Afterward, using a coupling fitting and tee-fitting, connect the pressure gauge and flow-restriction valve to the tube side outlet of the backward extraction membrane. Using flexible pump tubing, connect the tube side outlet at the top of the backward extraction membrane to the stripping solution reservoir return-flow port. To begin, integrate the bioreactor and liquid liquid extraction system.
Turn on the stripping solution peristaltic pump, or backward extraction membrane, and set the pump speed to achieve a constant flow rate between 25 to 250 milliliters per minute. Slowly close the needle valve at the shell-side outlet of the backward extraction membrane to establish a back pressure. Then, turn on the first hydrophobic hollow-fiber membrane module peristaltic pump, and set the pump speed to achieve a constant flow rate between 25 to 250 milliliters per minute.
Afterward, slowly close the needle valve at the shell-side outlet of the first hydrophobic hollow-fiber membrane module to establish a back pressure of approximately five pounds per square inch gauge. Now turn on the organic phase extraction solution diaphragm pump, and set the pump speed to achieve a constant flow rate between five to 50 milliliters per minute. Lastly, check the system for continuous flow.
A steady accumulation of short and medium chain fatty acid products was observed in the alkaline aqueous phase stripping solution. A reduction in pump speed lowered the extraction efficiency. After restoring adequate pump speed, efficiency may take several days to recover.
