David L. Grzenia

Membrane extraction for detoxification of biomass hydrolysates

Membrane extraction was used for the removal of sulfuric acid, acetic acid, 5-hydroxymethyl furfural and furfural from corn stover hydrolyzed with dilute sulfuric acid. Microporous polypropylene hollow fiber membranes were used. The organic extractant consisted of 15% Alamine 336 in: octanol, a 50:50 mixture of oleyl alcohol:octanol or oleyl alcohol. Rapid removal of sulfuric acid, 5-hydroxymethyl and furfural was observed. The rate of acetic acid removal decreased as the pH of the hydrolysate increased. Regeneration of the organic extractant was achieved by back extraction into an aqueous phase containing NaOH and ethanol. A cleaning protocol consisting of flushing the hydrolysate compartment with NaOH and the organic phase compartment with pure organic phase enabled regeneration and reuse of the module. Ethanol yields from hydrolysates detoxified by membrane extraction using 15% Alamine 336 in oleyl alcohol were about 10% higher than those from hydrolysates detoxified using ammonium hydroxide treatment.

Purification of Densonucleosis Virus by Tangential Flow Ultrafiltration

Purification at commercial scale of viruses and virus vectors for gene therapy applications and viral vaccines is a major separations challenge. Tangential flow ultrafiltration has been developed for protein purification. Here tangential flow ultrafiltration of parvoviruses has been investigated. Because these virus particles are small (18–26 nm), removal of host cell proteins will be challenging. The results obtained here indicate that 30, 50, and 100 kDa membranes reject the virus particles, whereas 300 kDa membranes allow some virus particles to pass into the permeate. The decrease in permeate flux for the 300 kDa ultrafiltration membrane is much greater than for the 30, 50, and 100 kDa membranes, indicating possible entrapment of virus particle in the membrane pores. The permeate flux and level of protein rejection is strongly affected by the cell culture growth medium. The results indicate that when developing a new process, it is essential that the cell culture and purification operations be developed in parallel.

Fermentation of Reactive-Membrane-Extracted and Ammonium-Hydroxide-Conditioned Dilute-Acid-Pretreated Corn Stover

Acid-pretreated biomass contains various compounds (acetic acid, etc.) that are inhibitory to fermentative microorganisms. Removing or deactivating these compounds using detoxification methods such as overliming or ammonium hydroxide conditioning (AHC) improves sugar-to-ethanol yields. In this study, we treated the liquor fraction of dilute-acid-pretreated corn stover using AHC and a new reactive membrane extraction technique, both separately and in combination, and then the sugars in the treated liquors were fermented to ethanol with the glucose–xylose-fermenting bacterium, Zymomonas mobilis 8b. We performed reactive extraction with mixtures of octanol/Alamine 336 or oleyl alcohol/Alamine 336. The best ethanol yields and rates were achieved for oleyl alcohol-extracted hydrolysates followed by AHC hydrolysates, while octanol-extracted hydrolysates were unfermentable because highly toxic octanol was found in the hydrolysate. Adding olive oil significantly improved yields for octanol-extracted hydrolysate. Additional work is underway to determine if this technology is a cost-effective alternative to traditional hydrolysate conditioning processes.

Chapter 10 - Membrane Extraction for Biofuel Production

Abstract Dispersion-free membrane-based solvent extraction has been shown to overcome many of the disadvantages associated with dispersion-based contacting devices used for conventional solvent extraction. Here, we have explored the use of membrane-based solvent extraction for the production of biofuels. Given the nonvolatile nature of most biomass components, it is likely that solvent extraction will dominate in future biorefineries. Three potential applications for membrane-based solvent extraction are considered. Production of biofuels from lignocellulosic biomass may be achieved through three main routes: gasification, pyrolysis or liquefaction, and hydrolysis. Hydrolysis of the lignocellulosic biomass leads to an aqueous sugar-rich solution which may be fermented to biofuels such as ethanol. The use of membrane-based solvent extraction has been investigated for removal of acetic acid from hydrolysates derived from sugarcane bagasse, sorghum, oats, coffee husks, corn fiber, and corn leaves prior to fermentation. Acetic acid is one of the products of hydrolysis that is toxic to the microorganism used to ferment the sugars to ethanol. The results obtained here indicate that membrane-based solvent extraction is a flexible unit operation that may be used to remove acetic acid from a variety of hydrolysates. Biomass hydrolysates may also be converted to fuels by aqueous phase processing. Hydroxymethylfurfural (HMF) is an important intermediate in this process. Membrane-based solvent extraction has been used to recover this valuable intermediate from an aqueous phase. In addition, membrane-based solvent extraction has been used to remove glycerol from butanol. This later separation could be of significance in the production of biodiesel. The results for the three extractions investigated here highlight the versatility of membrane-based solvent extraction for the production of biofuels. Experimentally determined overall mass transfer coefficients agree well with those predicted from theory. These coefficients may be predicted using mass transfer correlations found in the literature. These mass transfer coefficients could be used to guide the design of larger-scale processes.

Concentration and Purification of Densonucleosis Virus by Tangential Membrane Filtration and by Ion Exchange Membranes

In gene therapy and vaccine production, large-scale purification of virus vectors is often essential. In the manufacture of biopharmaceuticals, validation of virus clearance is critical. Tangential flow filtration is well established in the biotechnology industry for the purification and concentration of proteins. Also chromatography is widely used in downstream processing and the replacement of resins by membranes as chromatographic supports is of interest to overcome limitations associated with resin-based chromatography. Purification of the Aedes aegypti densonucleosis virus (AeDNV) using tangential flow filtration and also using anion and cation exchange membranes was investigated. The results showed that 30, 50, and 100 kDa membranes reject the virus particles in contrast to 300 kDa membranes. The permeate flux is strongly affected by the used medium. AeDNV particles may be adsorbed most effective by strongly basic anion exchange membranes.