Chitosan has been proposed as a "natural" coagulating agent to solve wastewater problems. The main hindrance in this commercial chitosan application has been its low cost effectiveness. The hypothesis in our research is that chitosan complexes with natural polyanions is more effective than chitosan alone, particularly in recovering low concentration proteins from food processing wastewater. Chitosan (Chi) was reacted with alginate (Alg), pectin (Pec) and carrageenan (Car) ex-situ to obtain chitosan-polyanion complexes (Chi-Pol). Analysis by Fourier Transform Infrared (FTER) spectroscopy confirmed electrostatic interactions as the mechanism for complex formation. Scanning electron microscopy revealed a tight, non-porous structure except for the porous Chi-Car complex. Tests with a bovine serum albumin solution revealed low adsorption rates with slightly higher values for Chi-Car suggesting the need for an improved complexation method. Chi-Pol complexes prepared in-situ at different monomeric weight ratios (MR) were evaluated using pH 6 adjusted Cheddar cheese whey and surimi wastewater (SWW). Complexes used at 30 mg complex/L whey showed higher turbidity reductions than at 10 mg/L. MR had no significant effect on turbidity reduction except for Chi-Alg at 30 mg/L; the value (72 %) at MR = 0.2 was higher than for MR = 0.8. UV-Vis spectroscopy confirmed in-situ complex formation with a preference for the adsorption of specific whey protein fractions. Complexes formed at 0.2 and 0.8 MR were evaluated at two concentrations for the treatment of SWW. Tests at 50 mg/L showed a turbidity reduction of up to 97 % at 24 h with a 81-90 % recovery of SWW proteins. At 150 mg/L, similar efficacy was achieved in only 1 h with turbidity reductions ranging 94-99 % and 78-94 % protein recovery. FTIR analyses confirmed the adsorption of proteins as indicated by similarities in the three amide bands for Chi-Alg recovered solids and untreated SWW. Differential scanning calorimetry (DSC) was employed to study interactions of SWW proteins and Chi-Alg complexes. Untreated and complex bound SWW proteins revealed single exothermic peaks at 23.3 and 38.0°C, respectively. This suggested Chi-Alg and SWW protein interactions increased the thermal stability of SWW proteins. However, further thermal analysis studies are needed to confirm this finding. / Graduation date: 2001

Interactions between proteins and contact surfaces can have important implications in the food industry. Such interactions contribute to the course of fouling of membrane surfaces and they appear to mediate bacterial and spore adhesion to some degree as well. In addition to protein and solution properties, interfacial behavior is strongly influenced by contact surface properties. Among these, hydrophobicity and the potential to take part in acid-base interaction have received considerable attention, but in a quantitative sense we know very little about their respective influences on protein adsorption. It was the purpose of this research to quantify the equilibrium adsorptive behavior of the milk protein β-lactoglobulin as it is influenced by the presence of different contact surface functional groups. Monocrystalline and polished silicon surfaces were modified to be hydrophilic by oxidation and hydrophobic by silanization with dichlorodiethylsilane (DDES), dichlorodimethylsilane (DDMS), and dichlorodiphenylsilane (DDPS), each used at concentrations of 0.82, 3.3, and 82 mM. Surface hydrophobicities were evaluated with contact angle methods. Adsorption isotherms were constructed after allowing each modified silicon surface to independently contact β-lactoglobulin (0.01 M phosphate buffer, pH 7.0) at concentrations ranging between 200 and 2000 mg/L for eight h at room temperature. Surfaces were then rinsed and dried. Optical properties of the bare- and film-covered surfaces, necessary for calculation of adsorbed mass, were obtained by ellipsometry. Plots of adsorbed mass as a function of protein concentration exhibited attainment of plateau values beyond a protein concentration of about 200 mg/L. At high silane concentration, the plateau values associated with surfaces exhibiting ethyl groups were observed to be greatest followed by those exhibiting phenyl, methyl, then hydrophilic (OH) groups. At the low DDMS and DDES concentrations (0.82 and 3.3 mM), adsorbed mass did not increase beyond that value recorded for the hydrophilic surface. This is likely due to some critical spacing of methyl and ethyl groups being required to produce a favorable hydrophobic effect on adsorption. For surfaces treated with dichlorodiphenylsilane, adsorbed mass increased with silane concentration. Apparently, a favorable acid-base interaction effected by the hydrophilic surface is inhibited by the presence of small amounts of methyl and ethyl groups, but somewhat less inhibited by the presence of phenyl groups because the latter have the ability to undergo acid-base interaction. / Graduation date: 1993

A significant advantage attributed to surge flow irrigation is that for the same volume of water applied the stream will advance farther along the furrow than with continuous flow. This potentially will reduce runoff and deep percolation which will improve uniformity and application efficiency where this advance phenomenon holds. The mechanism for improvement in advance time has generally been ascribed to surface sealing and surface layer consolidation. However, these phenomena do not satisfactorily explain improved advance times in sandy soils. Widely used infiltration equations which require the determination of empirical coefficients are unsatisfactory as predictors of infiltration conditions of intermittent wetting. The Green-Ampt model and a simple redistribution model are combined into an analytical model to predict infiltration under surge irrigation. The model results are compared to infiltration tests on soil columns of three soils of different soil textures. Also the model and the experimental results from the soil columns are compared to predictions made by two numerical solutions of the Richard's equation. One of the numerical models includes the effect of hysteresis by the use of Mualem's model to predict the variation of moisture content with potential, the other numerical model neglects the effect of hysteresis. A comparison of the analytical and the numerical models shows good agreement in their predictions for the soils and surge cycles tested. A comparison of predictions made by all three models shows good correlation to the experimental results. Although the number of tests done on the analytical model were limited it appears to be nearly as good a predictor of infiltration as the numerical models. The greatest strength of the analytical model is that while the numerical models took many hours to do a single run, the analytical model took only a few minutes. Both model and experimental results indicate that there was no reduction in infiltration rates or volumes infiltrated with intermittent as compared to continuous wetting. Thus the reduction in hydraulic gradient is not a factor in the reduced infiltration observed by others.

Oral drug administration remains the most popular route of drug delivery. Absorption of the dissolved drug through the intestinal epithelial membrane is a prerequisite to systemic bioavailability and drug efficacy. In efforts to reduce the long lead times, attrition rates, and costs of drug discovery and development, computational models have been developed to predict the membrane permeability and absorption efficiency of a dosed drug. Many models utilize various molecular descriptors to correlate with in vitro permeability or human intestinal absorption data. It is widely accepted that the two most significant physicochemical properties that control a compound's passive transport process are its aqueous solubility and lipophilicity characteristics.This work will discuss the theoretical background of passive transport, a number of computational models developed to predict in vitro permeability, other models that predict human fraction of dose absorbed, and predicting absorption efficiency relative to a maximum dose. A newly developed prediction method is also presented, that reveals an interesting relationship between fraction absorbed and the melting point of the drug.

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