Abstract:Producing fuels and chemical intermediates with cell cultures is severely limited by low product concentrations (≤0.2%(v/v)) due to feedback inhibition, cell instability, and lack of economical product recovery processes. We have developed an alternate simplified production scheme based on a cell-free immobilized enzyme system. Two immobilized enzymes (keto-acid decarboxylase (KdcA) and alcohol dehydrogenase (ADH)) and one enzyme in solution (formate dehydrogenase (FDH) for NADH recycle) produced isobutanol ti… Show more
“…A novel membrane to remove isobutanol in situ from a biofuels production system must not only be able to selectively remove isobutanol, but also should retain essential reactive compounds. Figure C shows the targeted immobilization reaction that requires selective removal of isobutanol using PV . Isobutanol must be separated from the other components that should be retained.…”
Section: Resultsmentioning
confidence: 99%
“…Figure 1C shows the targeted immobilization reaction that requires selective removal of isobutanol using PV. 43 Isobutanol must be separated from the other components that should be retained. Both the commercial PDMS membranes and the new C18 grafted brush membranes retain formate, β-nicotinamide adenine dinucleotide [reduced] (NADH), and ketoisovaleric acid; however, the novel grafted membrane retains isobutyraldehyde while the PDMS membranes do not (Figure 4B).…”
Isolating and concentrating volatile organics such as fuels and intermediate chemicals from aqueous solutions is important for environmental synthesis and processing. We have prepared a new class of easy-to-synthesize polymeric membranes comprising hydrophobic brush-like structures as a selective layer, and have tested them using pervaporation of isobutanol from water. These brush structures were prepared by graft-induced polymerization of hydrophobic vinyl monomers from light-sensitive poly(ether sulfone) nanofiltration support membranes (grafting from) without initiating agents. Graft-induced tethered polymer chains with multiple C18 alkane side-chains out-performed the industry gold standard silicone rubber membrane with selectivities of α = 10.1 ± 0.9 and 6.7 ± 0.1, respectively, at comparable permeation fluxes of 0.7− 1.0 ± 0.1 L/m 2 -h. Preparation of these brush membranes is simpler and easier to scale-up than current methods of preparing asymmetric and composite membrane structures. These brush structures and this method of preparation have excellent potential for synthesizing selective membranes suitable for large-scale organic−water separations.
■ INTRODUCTIONPressure-driven membrane filtration processes have matured and are now widely accepted in many industries such as in energy, biotechnology, food and beverage, chemical, wastewater, gas fractionation, and desalination due to their low energy requirements and one-phase operation. Although membranes made from metals or ceramics are available, polymeric materials predominate. 1 For over 40 years, both interfacial polymerization 2 and phase inversion 3 have been the predominant methods for preparing composite polymeric and asymmetric membrane structures, respectively. Although these synthesis methods have been very successful, they are both relatively complex and sensitive to small changes in the casting conditions. 4 Many research groups have sought novel synthesis methods for producing synthetic membranes without much success. These membranes suffer from limitations including low porosity (track etched), 5−7 high cost (ceramic or stainless steel), 8 wide pore size distribution (stretched PTFE), 9−11 and low strength (biological), 12 or are difficult to scale-up (zeolite, carbon-nanotubes or graphene oxide). 13−15 Here, we synthesize a new class of synthetic brush hydrophobic polymer membranes, and then test them with a challenging separation: removal of isobutanol from water by pervaporation (PV). 16 To prepare the best performing hydrophobic brush membranes for this separation, we used our unique high throughput platform with 96 filter well plates. 17 The method of preparation involves grafting commercially available vinyl monomers alone or in mixtures to light-sensitive poly(ether sulfone) (PES) nanofiltration membranes, screening for the best performers, and selecting the winners. 18−20 The high throughput platform has also been used with combinatorial chemistry to generate a library of new monomers. 19,21 The newly synthesized hydrophobic-terminat...
“…A novel membrane to remove isobutanol in situ from a biofuels production system must not only be able to selectively remove isobutanol, but also should retain essential reactive compounds. Figure C shows the targeted immobilization reaction that requires selective removal of isobutanol using PV . Isobutanol must be separated from the other components that should be retained.…”
Section: Resultsmentioning
confidence: 99%
“…Figure 1C shows the targeted immobilization reaction that requires selective removal of isobutanol using PV. 43 Isobutanol must be separated from the other components that should be retained. Both the commercial PDMS membranes and the new C18 grafted brush membranes retain formate, β-nicotinamide adenine dinucleotide [reduced] (NADH), and ketoisovaleric acid; however, the novel grafted membrane retains isobutyraldehyde while the PDMS membranes do not (Figure 4B).…”
Isolating and concentrating volatile organics such as fuels and intermediate chemicals from aqueous solutions is important for environmental synthesis and processing. We have prepared a new class of easy-to-synthesize polymeric membranes comprising hydrophobic brush-like structures as a selective layer, and have tested them using pervaporation of isobutanol from water. These brush structures were prepared by graft-induced polymerization of hydrophobic vinyl monomers from light-sensitive poly(ether sulfone) nanofiltration support membranes (grafting from) without initiating agents. Graft-induced tethered polymer chains with multiple C18 alkane side-chains out-performed the industry gold standard silicone rubber membrane with selectivities of α = 10.1 ± 0.9 and 6.7 ± 0.1, respectively, at comparable permeation fluxes of 0.7− 1.0 ± 0.1 L/m 2 -h. Preparation of these brush membranes is simpler and easier to scale-up than current methods of preparing asymmetric and composite membrane structures. These brush structures and this method of preparation have excellent potential for synthesizing selective membranes suitable for large-scale organic−water separations.
■ INTRODUCTIONPressure-driven membrane filtration processes have matured and are now widely accepted in many industries such as in energy, biotechnology, food and beverage, chemical, wastewater, gas fractionation, and desalination due to their low energy requirements and one-phase operation. Although membranes made from metals or ceramics are available, polymeric materials predominate. 1 For over 40 years, both interfacial polymerization 2 and phase inversion 3 have been the predominant methods for preparing composite polymeric and asymmetric membrane structures, respectively. Although these synthesis methods have been very successful, they are both relatively complex and sensitive to small changes in the casting conditions. 4 Many research groups have sought novel synthesis methods for producing synthetic membranes without much success. These membranes suffer from limitations including low porosity (track etched), 5−7 high cost (ceramic or stainless steel), 8 wide pore size distribution (stretched PTFE), 9−11 and low strength (biological), 12 or are difficult to scale-up (zeolite, carbon-nanotubes or graphene oxide). 13−15 Here, we synthesize a new class of synthetic brush hydrophobic polymer membranes, and then test them with a challenging separation: removal of isobutanol from water by pervaporation (PV). 16 To prepare the best performing hydrophobic brush membranes for this separation, we used our unique high throughput platform with 96 filter well plates. 17 The method of preparation involves grafting commercially available vinyl monomers alone or in mixtures to light-sensitive poly(ether sulfone) (PES) nanofiltration membranes, screening for the best performers, and selecting the winners. 18−20 The high throughput platform has also been used with combinatorial chemistry to generate a library of new monomers. 19,21 The newly synthesized hydrophobic-terminat...
Fermentation-derived alcohols have gained much attention as an alternate fuel due to its minimal effects on atmosphere. Besides its application as biofuel it is also used as raw material for coating resins, deicing fluid, additives in polishes, etc. Among the liquid alcohol type of fuels, isobutanol has more advantage than ethanol. Isobutanol production is reported in native yeast strains, but the production titer is very low which is about 200 mg/L. In order to improve the production, several genetic and metabolic engineering approaches have been carried out. Genetically engineered organism has been reported to produce maximum of 50 g/L of isobutanol which is far more than the native strain without any modification. In bacteria mostly last two steps in Ehrlich pathway, catalyzed by enzymes ketoisovalerate decarboxylase and alcohol dehydrogenase, are heterologously expressed to improve the production. Native
Saccharomyces cerevisiae
can produce isobutanol in negligible amount since it possesses the pathway for its production through valine degradation pathway. Further modifications in the existing pathways made the improvement in isobutanol production in many microbial strains. Fermentation using cost-effective lignocellulosic biomass and an efficient downstream process can yield isobutanol in environment friendly and sustainable manner. The present review describes the various genetic and metabolic engineering practices adopted to improve the isobutanol production in microbial strains and its downstream processing.
“…In vivo production of isobutanol is limited due to its toxicity on the strain producing it ( Chen and Liao, 2016 ; Dong et al, 2016 ). Even at concentrations as low as 1% (v/v), cells have shown signs of growth inhibition ( Grimaldi et al, 2016a ). Attempts have been made in the past to produce isobutanol by engineering E. coli, Bacillus subtilis and Corynebacterium glutamicum using a common strategy of expressing genes encoding KIVD from Lactococcus lactis and ADH from either Saccharomyces cerevisiae, C. glutamicum, E. coli or L. lactis (encoded by adh2 , adhA , yqhD and adhA , respectively), ( Atsumi et al, 2008a , 2010a ; Li et al, 2011 ; Smith et al, 2010 ; Blombach et al, 2011 ).…”
Section: Introductionmentioning
confidence: 99%
“…While there has been limited success with increasing isobutanol tolerance in vivo , there are still issues with product inhibition, product removal, and long-term industrial feasibility. In vitro production has been proposed as a solution to these in vivo problems ( Grimaldi et al, 2016a ). By selecting pathway enzymes from cells, the toxicity effects of isobutanol can be bypassed.…”
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