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Jang, Nulee,Yasin, Muhammad,Park, Shinyoung,Lovitt, Robert W.,Chang, In Seop Elsevier Applied Science 2017 Bioresource technology Vol.239 No.-
<P><B>Abstract</B></P> <P>A mathematical model of microbial kinetics was introduced to predict the overall volumetric gas–liquid mass transfer coefficient (<I>k</I> <SUB>L</SUB> <I>a</I>) of carbon monoxide (CO) in a batch cultivation system. The cell concentration (<I>X</I>), acetate concentration (<I>C<SUB>ace</SUB> </I>), headspace gas (<I>N<SUB>co</SUB> </I> and <SUB> N <SUB> co 2 </SUB> </SUB> ), dissolved CO concentration in the fermentation medium (<I>C<SUB>co</SUB> </I>), and mass transfer rate (<I>R</I>) were simulated using a variety of <I>k</I> <SUB>L</SUB> <I>a</I> values. The simulated results showed excellent agreement with the experimental data for a <I>k</I> <SUB>L</SUB> <I>a</I> of 13/hr. The <I>C<SUB>co</SUB> </I> values decreased with increase in cultivation times, whereas the maximum mass transfer rate was achieved at the mid-log phase due to vigorous microbial CO consumption rate higher than <I>R</I>. The model suggested in this study may be applied to a variety of microbial systems involving gaseous substrates.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First report of <I>k</I> <SUB>L</SUB> <I>a</I> for a batch cultivation system using kinetic simulation. </LI> <LI> Combined microbial kinetics and gas–liquid mass transfer. </LI> <LI> The dissolved CO concentration and mass transfer in a batch system were simulated. </LI> <LI> No dissolved CO assumption leads to a large error in simulating gas cultivation. </LI> </UL> </P>
Jang, Nulee,Yasin, Muhammad,Kang, Hyunsoo,Lee, Yeubin,Park, Gwon Woo,Park, Shinyoung,Chang, In Seop Elsevier 2018 Bioresource technology Vol.263 No.-
<P><B>Abstract</B></P> <P>This study investigated the effects of electrolytes (CaCl<SUB>2</SUB>, K<SUB>2</SUB>HPO<SUB>4</SUB>, MgSO<SUB>4</SUB>, NaCl, and NH<SUB>4</SUB>Cl) on CO mass transfer and ethanol production in a HFMBR. The hollow fiber membranes (HFM) were found to generate tiny gas bubbles; the bubble coalescence was significantly suppressed in electrolyte solution. The volumetric gas-liquid mass transfer coefficients (<I>k</I> <SUB>L</SUB> <I>a</I>) increased up to 414% compared to the control. Saturated CO (<I>C</I> <SUP>∗</SUP>) decreased as electrolyte concentrations increased. Overall, the maximum mass transfer rate (<I>R</I> <SUB>max</SUB>) in electrolyte solution ranged from 106% to 339% of the value obtained in water. The electrolyte toxicity on cell growth was tested using <I>Clostridium autoethanogenum</I>. Most electrolytes, except for MgSO<SUB>4</SUB>, inhibited cell growth. The HFMBR operation using a medium containing 1% MgSO<SUB>4</SUB> achieved 119% ethanol production compared to that without electrolytes. Finally, a kinetic simulation using the parameters got from the 1% MgSO<SUB>4</SUB> medium predicted a higher ethanol production compared to the control.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Microbubble generation using electrolytes in HFMBR without mechanical mixing. </LI> <LI> Change in mass transfer rate depends on electrolyte type and concentration. </LI> <LI> First application of electrolyte-based mass transfer system to syngas fermentation. </LI> <LI> Microbial growth and ethanol production can be supported by electrolyte-based HFMBR. </LI> </UL> </P>