Synthesis of Cellulose-graft-Polypropionic Acid Nanofiber Cation-Exchange Membrane Adsorbers for High-Efficiency Separations.

Fabrication of membrane adsorbers with elevated binding capacity and high throughput is highly desired for simplifying and improving purification efficiencies of bioproducts (biotherapeutics, vaccines, etc.) in the biotechnological and biopharmaceutical industries. Here we demonstrate the preparation of a novel class of self-supported, cellulose-graft-polypropionic acid (CL-g-PPA) cation-exchange nanofiber membrane adsorbers under mild reaction conditions for the purification of positively charged therapeutic proteins.

Hot-pressed polymer nanofiber supported graphene membrane for high-performance nanofiltration.

Graphene oxide (GO) sheets can be readily surface-overlaid on hot-pressed electrospun polyacrylonitrile (PAN) nanofiber membrane to form a continuous and crack-free layer; upon thermal reduction at 150 °C for 12 h, the resulting reduced GO (rGO) layer can reject ∼90% MgSO with high water flux (due to the size exclusion mechanism), making the prepared PAN-rGO membranes promising nanofiltration media for water purification. It is important to note that no delamination of GO/rGO sheet layers has been observed throughout this study. We highlight that a simple processing method (i.

Electrospun Regenerated Cellulose Nanofiber Membranes Surface-Grafted with Water-Insoluble Poly(HEMA) or Water-Soluble Poly(AAS) Chains via the ATRP Method for Ultrafiltration of Water.

Electrospun nanofiber membranes (ENMs) have demonstrated promising applications for water purification primarily due to high water flux and low degree of fouling. However, the equivalent/apparent pore sizes of as-electrospun ENMs are in microns/submicrons; therefore, the ENMs can only be directly utilized for microfiltration applications. To make regenerated cellulose (RC) ENMs for ultrafiltration applications, atom transfer radical polymerization (ATRP) was studied to graft polymer chains onto the surface of RC nanofibers; specifically, monomers of 2-hydroxyethyl methacrylate (HEMA) and sodium acrylate (AAS) were selected for surface-grafting water-insoluble and water-soluble polymer chains onto RC nanofibers, respectively.

Polyacrylonitrile nanofiber membranes modified with ionically crosslinked polyelectrolyte multilayers for the separation of ionic impurities.

Nanofiltration membranes were prepared by forming multilayers of branched polyethylenimine (BPEI) and polyacrylic acid (PAA) on a polyacrylonitrile (PAN) nanofibrous mat by layer-by-layer (LbL) assembly. The degree of ionization (DI) of PAA, estimated using FTIR spectra both in the absence and presence of added salt, was shown to have a strong influence on the BPEI/PAA film growth. BPEI/PAA multilayers grew exponentially when the DI of PAA was less than 30%, or when the pH of PAA during LbL formation was less than 3.

Comparative technoeconomic analysis of a softwood ethanol process featuring posthydrolysis sugars concentration operations and continuous fermentation with cell recycle.

Economical production of second generation ethanol from Ponderosa pine is of interest due to widespread mountain pine beetle infestation in the western United States and Canada. The conversion process is limited by low glucose and high inhibitor concentrations resulting from conventional low-solids dilute acid pretreatment and enzymatic hydrolysis. Inhibited fermentations require larger fermentors (due to reduced volumetric productivity) and low sugars lead to low ethanol titers, increasing distillation costs.

Quantifying second generation ethanol inhibition: Design of Experiments approach and kinetic model development.

While softwoods represent a potential feedstock for second generation ethanol production, compounds present in their hydrolysates can inhibit fermentation. In this study, a novel Design of Experiments (DoE) approach was used to identify significant inhibitory effects on Saccharomyces cerevisiae D5A for the purpose of guiding kinetic model development. Although acetic acid, furfural and 5-hydroxymethyl furfural (HMF) were present at potentially inhibitory levels, initial factorial experiments only identified ethanol as a significant rate inhibitor.

Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.

In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ∼200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e.

Continuous enzymatic hydrolysis of lignocellulosic biomass with simultaneous detoxification and enzyme recovery.

Recovering hydrolysis enzymes and/or alternative enzyme addition strategies are two potential mechanisms for reducing the cost during the biochemical conversion of lignocellulosic materials into renewable biofuels and biochemicals. Here, we show that enzymatic hydrolysis of acid-pretreated pine wood with continuous and/or fed-batch enzyme addition improved sugar conversion efficiencies by over sixfold. In addition, specific activity of the hydrolysis enzymes (cellulases, hemicellulases, etc.

Membrane separations for solid-liquid clarification within lignocellulosic biorefining processes.

Membrane separations can be integrated into a biorefinery to reduce water and energy consumption. Unfortunately, current membrane materials suffer from severe fouling, which limits their applicability. Here, using analytical characterizations along with fouling models, we correlate membrane properties with performance metrics to provide a framework for optimal membrane selection during solid-liquid clarification of a biomass hydrolysate.

Mathematical model using non-uniform flow distribution for dynamic protein breakthrough with membrane adsorption media.

A mathematical model has been investigated to predict protein breakthrough during membrane adsorption/chromatography operations. The new model incorporates a non-uniform boundary condition at the column inlet to help describe the deviation from plug flow within real membrane adsorption devices. The model provides estimated breakthrough profiles of a binding protein while explicitly accounting for non-uniform flow at the inlet of the separation operation by modeling the flow distribution by a polynomial.

Surface-functionalized electrospun carbon nanofiber mats as an innovative type of protein adsorption/purification medium with high capacity and high throughput.

Due to recent advances in the production of biotherapeutics, high capacity, high throughput adsorption media for efficient and economic separation of these medically important products are in great demand. One option that has been evaluated extensively is membrane/mat adsorption. While these media allow for rapid adsorption (due to the decreased internal diffusion) and high throughput processing (due to the open porous structure), they often suffer from low capacity and poor enrichment factors.

Removal of enzymatic and fermentation inhibitory compounds from biomass slurries for enhanced biorefinery process efficiencies.

Within the biorefinery paradigm, many non-monomeric sugar compounds have been shown to be inhibitory to enzymes and microbial organisms that are used for hydrolysis and fermentation. Here, two novel separation technologies, polyelectrolyte polymer adsorption and resin-wafer electrodeionization (RW-EDI), have been evaluated to detoxify a dilute acid pretreated biomass slurry. Results showed that detoxification of a dilute acid pretreated ponderosa pine slurry by sequential polyelectrolyte and RW-EDI treatments was very promising, with significant removal of acetic acid, 5-hydroxymethyl furfural, and furfural (up to 77%, 60%, and 74% removed, respectively) along with >97% removal of sulfuric acid.

Process and economic evaluation for monoclonal antibody purification using a membrane-only process.

In recent years, the market for therapeutic monoclonal antibodies (mAb) has grown exponentially, and with this there has been a desire to reduce the costs associated with production and purification of these high-value biological products. A typical mAb purification process involves three adsorption/chromatography steps [protein A, ion exchange (IEX), and hydrophobic interaction (HIC)], along with ultrafiltration, nanofiltration, and microfiltration. With the development of membrane adsorption/chromatography as a viable alternative to traditional pack bed systems, the opportunity exists to complete the entire downstream purification process using only membrane operations.

Removal and recovery of furfural, 5-hydroxymethylfurfural, and acetic acid from aqueous solutions using a soluble polyelectrolyte.

In the cellulosic ethanol process, furfural, 5-hydroxymethylfurfural (HMF), and acetic acid are formed during the high temperature acidic pretreatment step needed to convert biomass into fermentable sugars. These compounds can inhibit cellulase enzymes and fermentation organisms at relatively low concentrations (≥ 1 g/L). Effective removal of these inhibitory compounds would allow the use of more severe pretreatment conditions to improve sugar yields and lead to more efficient fermentations; if recovered and purified, they could also be sold as valuable by-products.

Detoxification of a lignocellulosic biomass slurry by soluble polyelectrolyte adsorption for improved fermentation efficiency.

This study investigated the detoxification of a dilute acid pretreated Ponderosa pine slurry using the polyelectrolyte polyethyleneimine (PEI). The addition of polyelectrolyte to remove enzymatic and/or fermentation inhibitory compounds, that is, acetic acid, furfural, and 5-hydroxymethylfurfural (HMF), was performed either before or after enzymatic hydrolysis to determine the optimal process sequence. Negligible acetic acid, glucose, and xylose were removed regardless of where in the process the polymer addition was made.

Electrospun nanofiber membranes surface functionalized with 3-dimensional nanolayers as an innovative adsorption medium with ultra-high capacity and throughput.

Electrospun nanofiber membranes surface functionalized with 3D nanolayers through ATRP provide adsorption capacities over 50-times higher than current commercial membrane adsorption systems and over 12-times higher than packed bed resins; additionally, the adsorption kinetics remain 10-times faster than packed bed resins and have over 15-times higher permeance.

Polyelectrolyte flocculation of grain stillage for improved clarification and water recovery within bioethanol production facilities.

Polyelectrolytes were investigated for flocculation of a corn whole stillage stream to improve solid-liquid clarification operations and reduce downstream utility requirements for evaporation and drying within a bioethanol process. Despite a negative zeta potential for the stillage solids, an anionic polyelectrolyte was found to provide the best flocculation. At the optimal dosage of 1.

Recovery of proteins from corn and soybean extracts by membrane adsorption.

Efficient separation strategies for the recovery of high-value proteins (native or recombinant) from plant agriculture are an important aspect of many different processes, from biopharmaceuticals to byproduct recovery during biofuel production. Here we report the use of membrane adsorption for the recovery of proteins from soybean and corn extracts, and compare the results with packed bed adsorption. Two alternative operating modes were investigated, a flowthrough strategy and a bind and elute method.

Antibody capture from corn endosperm extracts by packed bed and expanded bed adsorption.

Topical treatments of chronic infections with monoclonal antibodies will require large quantities of antibodies. Because plants have been proven capable of producing multisubunit antibodies and provide for large-scale production, they are likely hosts to enable such applications. Recovery costs must also be low because of the relatively high dosages required.

Considerations for the recovery of recombinant proteins from plants.

The past 5 years have seen the commercialization of two recombinant protein products from transgenic plants, and many recombinant therapeutic proteins produced in plants are currently undergoing development. The emergence of plants as an alternative production host has brought new challenges and opportunities to downstream processing efforts. Plant hosts contain a unique set of matrix contaminants (proteins, oils, phenolic compounds, etc.

Compatibility of column inlet and adsorbent designs for processing of corn endosperm extract by expanded bed adsorption.

Corn has emerged as a viable host for expression of recombinant proteins; targeted expression to the endosperm has received particular attention. The protein extracts from corn endosperm differ from those of traditional hosts in regard to the nature of residual solids and extracted matrix contaminants. Each of these differences presents reasons for considering expanded bed adsorption for product capture and new considerations for limitations of the method.

Recombinant protein purification from pea.

To assess the suitability of transgenic peas as a host for protein production from the perspective of ease of recovery, a strain containing recombinant beta-glucuronidase with poly(histidine) tail (GUSH6) was evaluated for solubility of the target protein in relation to native components (proteins, carbohydrates, and phenolics). Recovery of the recombinant GUSH6 from aqueous extracts by immobilized metal affinity chromatography with coupled Co(2+) yielded a nearly pure product with IDA (enrichment factor (EF) = 260) or NTA (EF = 200) resin. Single-step recoveries were also possible by isoelectric precipitation (EF = 4), polyelectrolyte precipitation (EF = 1.

Host selection as a downstream strategy: polyelectrolyte precipitation of beta-glucuronidase from plant extracts.

Host selection can be a strategy to simplify downstream processing for protein recovery. Advancing capabilities for using plants as hosts offers new host opportunities that have received only limited attention from a downstream processing perspective. Here, we investigated the potential of using a polycationic precipitating agent (polyethylenimine; PEI) to precipitate an acidic model protein (beta-glucuronidase; GUS) from aqueous plant extracts.