We have investigated the relative performance of the two enzymes, -amylase and amyloglucosidase, and two microbial strains, Zymomonas mobilisAX101 and 8b, for saccharification and fermentation of sweet potato. Modified Michaelis-Menten and Monod-type mathematical models were developed and verified with experimental results for saccharification using amyloglucosidase and fermentation using Z.mobilis 8b, respectively. The results showed that 91.5% of the starch and sucrose were converted to glucose and fructose using amyloglucosidase at pH 3.5 and 55C. The Z.mobilis 8b was able to convert more than 90% of the total sugars into ethanol within 18h with 87.2% of the theoretical yield and 49.07g/L final concentration of ethanol. A mass balance and cost analysis show that commercial production of ethanol from sweet potato is limited by the feedstock cost.Practical ApplicationsThis study shows that sweet potatoes that are unmarketable, small in size, bruised, cut or damaged otherwise from the harvesting process, supplied by a local farmer in the Central Texas area, can be used to produce bioethanol. Normally, farmers do not collect the damaged sweet potatoes because there is no demand for those in the market. This is supported by the fact that 20% of the total sweet potatoes cultivated are left in the ground due to damage while harvesting with plows. If collected and used for ethanol production, local farms can earn additional revenue.

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.

The cytotoxicity of fullerene C60 particles on two mammalian cell lines, i.e. the Chinese hamster ovary (CHO) cells and the Madin-Darby canine kidney (MDCK) cells, has been investigated. Although innate fullerene particles have a very low solubility in deionized (DI) water, these particles can be dissolved in the tetrahydrofuran (THF) solvent at a great value. Further, the dissolved fullerene particles in the THF solvent could be extracted into a DI water solution at a significantly increased solubility. The formation of fullerene particle aggregates is believed to be the cause of the increased solubility. Results presented here show that once the concentration of the fullerene aggregates reaches a certain level, the cells start to die. The lethal dosage LD50, which is defined as the lowest fullerene concentration that results in a 50% cell death within 24 h, has been determined. Furthermore, the percentage of cell mortality increased with increasing fullerene concentration and incubation time yielding a negative effect on cell viability. These results, illustrated by atomic force microscopy (AFM), dynamic light scattering (DLS) and other microscopic techniques, will help to better understand the side effects of fullerene particles in mammalian cells.

We studied the influence of the gelation conditions on the formation kinetics of the polyphthalazine ether sulfone ketone (PPESK) membrane via wet phase inversion process experimentally and theoretically. Membrane formation and its morphology were first observed with an online optical microscope - CCD camera system. The resulting membranes prepared under various gelation conditions were then characterized by the gelation parameter, optical microscope, and SEM. Lastly, the relationship between the final membrane structure/permeation properties and the gelation parameter was discussed extensively. The results showed that both the gelation rate and the membrane flux increased dramatically as the gelation temperature increased. Moreover, the membrane structures became loose, and the porosity of membrane increased. Different non-solvent could change the solubility parameter between the polymer and the non-solvent, and thus the gelation rate greatly. With the increasing number of carbons in non-solvent, the gelation rate became slow, and the membrane gradually changed from a finger structure into a sponge structure. Adding NMP into the non-solvent changed the difference in the chemical potential and the solubility parameter between the polymer solution and the non-solvent, which in turn changed the gelation rate of polymer solution greatly. With the increasing concentration of NMP in non-solvent, the gelation rate became very slow and sponge structures formed with the non-solvent system of 80% NMP. A novel conclusion could be made that we could control the flux and reject of membrane just by changing the mean diffusion coefficient of skin, D, and the diffusion coefficient of skin, D1, in the process of membrane formation.

Virus capture is critical in a number of applications. 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 frequently used in the biotechnology industry for the purification of proteins. Also preparative chromatography is widely used in downstream purification procedures of biopharmaceutical products. Replacement of resins by membranes as chromatographic supports overcomes many of the limitations associated with resin-based chromatography. In particular, adsorptive membranes may be ideally suited for virus capture. Purification of the Aedes aegypti densonucleosis virus (AeDNV, a nonenveloped single-stranded mosquito-specific parvovirus, particle size about 26 nm) using tangential flow filtration and also using anion and cation exchange membranes was investigated. The results obtained here indicate that 30, 50, and 100 kDa membranes reject the virus particles, whereas 300 kDa membranes allow virus particles to pass into the permeate. The decrease in permeate flux for the 300 kDa ultrafiltration membrane is much greater than for the other membranes. This indicates a possible entrapment of virus particles in the membrane pores. The permeate flux and level of protein rejection are strongly affected by the cell culture growth medium. AeDNV particles may be adsorbed by both anion and cation exchange membranes by adjusting the pH of the feed stream. However, strongly basic anion exchange membranes were the most effective in adsorbing AeDNV particles.

Flocculation of the Escherichia coli lysate has been investigated. Three different types of commercially available synthetic polymers have been used as the flocculants. These polymers have different structures and charge characteristics. Two of them are 100% positively charged while the charge density of the third flocculant is pH dependent. For each type of the flocculants, several polymers with different molecular weights have been investigated. The flocculation results demonstrate that all the polymers tested can effectively flocculate the E. coli lysate. However, their flocculation efficiency is different. The polymer structure plays a very important role on the flocculation of the E. coli lysate. The effect of the molecular weight on the flocculation behavior is also observed for some flocculants. However, the effect of the charge density is not very important. The enhancement of the flocculation prior to a microfiltration of the E. coli lysate has been observed. The results clearly show that the flocculation prior to the microfiltration could greatly enhance the performance of the microfiltration process.

Intra- and inter-patient variability poses a challenging task to control blood glucose concentration in diabetic patients. A data based model predictive control with state and disturbance estimation has been developed to control the blood glucose concentration in the type-I diabetic patients in the presence of meal disturbances under patient-model mismatch. Simulation studies were performed on three distinct patient models generated as a result of sensitivity analysis, which revealed that the proposed control strategy is able to control the blood glucose concentration well within the acceptable limits and also able to compensate for the slow parametric drifts.

Gas-filled membrane absorption has been used to remove cyanide from different cyanide containing wastewaters. In this study, cyanide removal from an industrial praziquantel wastewater has been investigated. The wastewater contained a high cyanide concentration and turbidity due to the presence of lipophilic colloids. During cyanide removal, the membrane was severely fouled by these lipophilic colloids. In order to overcome membrane fouling, an integrated coagulation–gas-filled membrane absorption process is proposed. Coagulation is used to remove the lipophilic colloids before cyanide removal in the subsequent gas-filled membrane absorption step. By using this integrated process, the turbidity of the wastewater was decreased from 100–800 NTU to 10–40 NTU. Further the cyanide concentration was reduced from 1000–3500 mg/L to below 0.5 mg/L. More than 98% of the cyanide could be recovered and reused.

Acetic acid is a compound commonly found in hemicellulosic hydrolysates. This weak acid strongly influences the bioconversion of sugar containing hydrolysates. Previous investigators have used anion exchange resins for acetic acid removal from different hemicellulosic hydrolysates. In this study, the efficiency of an anion exchange membrane was compared to that of an anion exchange resin, for acetic acid removal from a DI water solution and an acidic hemicellulose hydrolysate pretreated using two different methods. Ion exchange membranes and resins have very different geometries. Here the performance of membranes and resins is compared using two dimensionless parameters, the relative mass throughput and chromatographic bed number. The relative mass throughput arises naturally from the Thomas solution for ion exchange. The results show that the membrane exhibit better performance in terms of capacity, and loss of the desired sugars. In addition acetic acid may be eluted at a higher concentration from the membrane thus leading to the possibility of recovery and re-use of the acetic acid.

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.

Formation kinetics of the poly (phthalazinone ether sulfone ketone) (PPESK) asymmetric membrane via wet phase-inversion process has been studied experimentally. The membrane morphology has been observed using an online optical microscope-CCD camera experimental system. The precipitation front movement, X, has been measured. Three different linear correlations between the value of X-2 and the gelation time, t, have been identified. This observation is different from a commonly accepted conclusion which assumed a single linear correlation between X2 and t for the whole gelation process. Compared to the morphology evolution of the membrane, it is realized that these three correlations correspond to the three consecutive gelation steps: formation of the top layer, formation of the transition layer and formation of the support layer. The effect of two additives, PEG 1000 and Tween80, on the formation kinetics as well as the membrane flux has also been studied. The results present here may provide better understanding of the asymmetric membrane formation process. (c) 2005 Elsevier B.V. All rights reserved.

Experimental and numerical results for binding Aedes aegypti densonucleosis virus (AeDNV) using anion and cation exchange membranes are presented. AeDNV particles are adsorbed by anion and cation exchange membranes providing the virus particles and membranes are oppositely charged. Q membranes which are strongly basic anion exchangers were the most effective. Dynamic and static capacities for Q membranes were found to be similar. A numerical model is proposed which assumes a log normal pore size distribution. By estimating the required parameters from static binding experiments, the model may be used to calculate the breakthrough curve for virus adsorption.

Results are presented for the removal of cyanide from four different wastewaters using hollow–fiber gas membranes. The pilot–scale membrane facility had a maximum treatment capacity of 1000 L using 10 hollow–fiber modules with a total membrane surface area of 180 m 2 . The results are in general agreement with previous laboratory–scale studies. However, different wastewaters contain different dissolved solutes. These dissolved solutes reduce the predicted efficiency of the cyanide removal process and the purity of the recovered cyanide. Other volatile species present in the wastewater could be removed with the cyanide into the strip solution. Further osmotic pressure differences between the wastewater and strip solution could lead to water vapor passing through the gas–filled pores of the microporous hollow–fiber membranes.

Back-extraction of Pu4+ from a mixture of 20% tributyl phosphate (TBP) and 20% mixed trialkyl phosphine oxides (TRPO) in kerosene in the presence of UO22+ was studied. The back-extractants investigated may be divided into three groups: carboxylic acids and salts, amino polycarboxylates, and phosphonic acid. The distribution coefficients of both Pu4+ and UO22+ using a number of different back-extractants were measured and compared. The results obtained suggest that the only practical back-extractants are carboxylic acids. Among the carboxylic acids tested, oxalic acid is suitable when the UO22+ concentration in the organic phase is less than 2 g/L. For UO22+ concentrations between 2 and 10 g/L, oxalic acid-nitric acid mixtures may be used. For UO22+ concentrations greater than 10 g/L, the only practical back-extractant is glycolic acid. The results obtained here may be used to further develop a new process for separation of Pu4+ and UO22+ from TBP-TRPO/kerosene mixture.

Results of an experiment on the removal of cyanide from two industrial wastewaters by using gas-filled hollow fiber membranes in a pilot plant in China are presented. The plant was operated in batch mode using 1000L of feed solution. The plant contained 10 hollow fiber modules with a total effective membrane surface area of 180 m(2). The strip stream consisted of a 10% NaOH solution. The overall mass transfer coefficient for cyanide was determined experimentally. A decrease in the overall mass transfer coefficient with time was observed for real wastewaters due to fouling of the membrane. In particular, the presence of particulate matter in the wastewater can lead to a significant decrease in the overall mass transfer coefficient and, hence, the rate of cyanide removal. Various cleaning strategies were investigated in order to regenerate the membrane. The gas-filled membranes were stable for over two months of continuous operation when they were used with industrial wastewaters.

Arsenic contamination of drinking water is a concern in many parts of the world. In the United States, the Environmental Protection Agency recently reduced the maximum contaminant level of arsenic in drinking water from 50 to 10 μ/L (ppb). In Bangladesh the arsenic concentration in drinking water can be as high as hundreds of parts per billion while the maximum contaminant level is 50 ppb. Consequently, there is a great need for new cost-effective methods to remove arsenic from drinking water. Here arsenic removal by coagulation and filtration was investigated using groundwater from a city in southern Colorado in the United States and from Sonargaon in Bangladesh. The results of the bench-scale experiments conducted indicate that coagulation with ferric ions followed by filtration is effective in reducing arsenic concentration in the water tested. However, the actual efficiency of removal is highly dependent on the raw water quality. Further, addition of a polyelectrolyte coagulant aid may lead to improved permeate fluxes during tangential flow microfiltration but has little effect on the residual arsenic concentration.