Eunsung Kan

Scale-up and Cost Evaluation of a Foamed Emulsion Bioreactor

In the present paper, the potential of the foamed emulsion bioreactor (FEBR), a novel biological reactor for air pollution control was evaluated. Experimental data obtained on a laboratory-scale prototype were used to scale-up the process for a hypothetical case consisting of a contaminated air flow rate of 10,000 m3 h−1, a toluene inlet concentration of 1 g m−3 and minimum required treatment efficiency of 92%. Reactor design and operating issues for the full-scale FEBR were identified. They included the requirement for stable foam generation with appropriate air distributors, and recycling of the auxiliary organic phase, surfactants and cells from the discharge of the reactor. The capital and operating costs for the concept full-scale FEBR were evaluated and compared to those of competing technologies, namely biofiltration, biotrickling filtration and catalytic and thermal oxidation. All three biological techniques had significantly lower capital and operating costs. Among the biological techniques, the FEBR had the lowest estimated capital cost since its greater effectiveness allowed a smaller reactor to meet the treatment objectives. The operating costs for the FEBR were higher than those of biofilters and biotrickling filters because of the requirements for nutrients and auxiliary chemicals. Overall, the results highlight that biotreatment is much more cost effective than thermal and catalytic oxidation. They further suggest that the FEBR may an interesting alternative to biofilters and biotrickling filters where the available space for air pollution control equipment is limited

Carbon dioxide capture using Escherichia coli expressing carbonic anhydrase in a foam bioreactor

ABSTRACT The present study reports CO2 capture and conversion to bicarbonate using Escherichia coli expressing carbonic anhydrase (CA) on its cell surface in a novel foam bioreactor. The very large gas–liquid interfacial area in the foam bioreactor promoted rapid CO2 absorption while the CO2 in the aqueous phase was subsequently converted to bicarbonate ions by the CA. CO2 gas removal in air was investigated at various conditions such as gas velocity, cell density and CO2 inlet concentration. Regimes for kinetic and mass transfer limitations were defined. Very high removal rates of CO2 were observed: 9570 g CO2 m−3 bioreactor h−1 and a CO2 removal efficiency of 93% at 4% inlet CO2 when the gas retention time was 24 s, and cell concentration was 4 gdw L−1. These performances are superior to earlier reports of experimental bioreactors using CA for CO2 capture. Overall, this bioreactor system has significant potential as an alternative CO2 capture technology.

Influence of ionic liquids as solvents for the chemical synthesis of poly(3-octylthiophene) with FeCl3

Ionic liquids (ILs) were used as solvents for the FeCl3-catalyzed oxidative polymerization of 3-octylthiophene (3OT) for the first time. An excellent yield of 99% was obtained by using 1-butyl-3-methylimidazolium hexafluoroantimonate. The effect of the IL structure on the oxidative polymerization of 3OT was analyzed by the linear solvation energy relationship equation.

Modeling of a Foamed Emulsion Bioreactor: II. Model Parametric Sensitivity

The sensitivity of a conceptual model of a foam emulsion bioreactor (FEBR) used for the control of toluene vapors in air was examined. Model parametric sensitivity studies showed which parameters affect the removal of toluene (as model pollutant) in the FEBR the most significantly, and enabled definition of the limits of the process. Detailed examination of the results indicated that the process is highly complex and that both mass transfer and kinetic limitations can coexist in the bioreactor system. These results will help with the optimization of the design and operation of FEBRs. Biotechnol. Bioeng. 2009; 102: 708–713.

Effects of novel auto-inducible medium on growth, activity and CO₂ capture capacity of Escherichia coli expressing carbonic anhydrase.

A glucose-based auto-inducible medium (glucose-AIM) has been developed to enhance both growth and expression of lac operon-linked carbonic anhydrase (CA) expression in a recombinant strain of Escherichia coli. When the E. coli expressing CA was grown on various media, the glucose-based auto-inducible medium (glucose AIM) resulted in a CA activity of 1022 mU OD(600 nm)(-1) mL(-1) at 24 h and a specific growth rate of 0.082 h(-1). The CA activity was four to fourteen times higher than those by LB-IPTG. The E. coli expressing CA grown on the glucose-AIM showed highest activity at pH8.5 while it kept high stability up to 40°C and an inlet CO2 concentration of 6%. These findings indicate that the glucose-AIM would be a cost-effective medium to support high cell growth, CA activity and stability for effective CO2 capture.