Low-energy conformers of five α-(1,4)- and α-(1,6)-linked glucosyl trisaccharides were flexibly docked into the glucoamylase active site using AutoDock 2.2. To ensure that all significant conformational space was searched, the starting trisaccharide conformers for docking were all possible combinations of the corresponding disaccharide low-energy conformers. All docked trisaccharides occupied subsites −1 and +1 in very similar modes to those of corresponding nonreducing-end disaccharides. For linear substrates, full binding at subsite +2 occurred only when the substrate reducing end was α-(1,4)-linked, with hydrogen-bonding with the hydroxymethyl group being the only polar interaction there. Given the absence of other important interactions at this subsite, multiple substrate conformations are allowed. For the one docked branched substrate, steric hindrance in the α-(1,6)-glycosidic oxygen suggests that the active-site residues have to change position for hydrolysis to occur. Subsite +1 of the glucoamylase active site allows flexibility in binding but, at least inAspergillus glucoamylases, subsite +2 selectively binds substrates α-(1,4)-linked between subsites +1 and +2. Enzyme engineering to limit substrate flexibility at subsite +2 could improve glucoamylase industrial properties.

This is the twenty-second of a series of symposia devoted to talks and posters by students about their biochemical engineering research. The first, third, fifth, ninth, twelfth, sixteenth, and twenti~th were hosted by Kansas State University, the second and fourth by the University of Nebraska- Lincoln, the sixth, seventh, tenth, thirteenth, seventeenth, and twenty-second by Iowa State University, the eighth, fourteenth, and nineteenth by the University of Missouri-Columbia, the eleventh, fifteenth, and twenty-first by Colorado State University, and the eighteenth by the University of Colorado. Next year's symposium will be at the University of Oklahoma. Symposium proceedings are edited and issued by faculty of the host institution. Because final publication usually takes place in refereed journals, articles included here are brief and often cover work in progress.

Contents
C. A. Baldwin, J.P. McDonald, and L. E. Erickson, Kansas State University. Effect of Hydrocarbon Phase on Kinetic and Transport Limitations for Bioremediation of Microporous Soil

J. C. Wang, S. K. Banerji, and Rakesh Bajpai, University of Missouri-Columbia. Migration of PCP in Soil-Columns in Presence of a Second Organic Phase

Cheng-Hsien Hsu and Roger G. Harrison, University of Oklahoma. Bacterial Leaching of Zinc and Copper from Mining Wastes

James A. Searles, Paul Todd, and Dhinakar S. Kompala, University of Colorado. Suspension Culture of Chinese Hamster Ovary Cells Utilizing Inclined Sedimentation

Ron Beyerinck and Eric H. Dunlop, Colorado State University. The Effect of Feed Zone Turbulence as Measured by Laser Doppler Velocimetry on Baker's Yeast Metabolism in a Chemostat

Paul Li-Hong Yeh, GraceY. Sun, Gary A. Weisman, and Rakesh Bajpai, University of Missouri-Columbia. Effect of Medium Constituents upon Membrane Composition of Insect Cells

R. Shane Gold, M. M. Meagher, R. Hutkins, and T. Conway, University of Nebraska-Lincoin. Ethanol Tolerance and Carbohydrate Metabolism in Lactobacilli

John Sargantanis and M. N. Karim, Colorado State University. Application of Kalman Filter and Adaptive Control in Solid Substrate Fermentation

D. Vrana, M. Meagher, and R. Hutkins, University of Nebraska-Lincoln. Product Recovery Optimization in the ABE Fermentation

Kalyan R. Tadikonda and Robert H. Davis, University of Colorado. Cell Separations Using Targeted Monoclonal Antibodies Against Surface Proteins

Meng H. Heng and Charles E. Glatz, Iowa State University. Charged Fusion for Selective Recovery of B-Galactosidase from Cell Extract Using Hollow Fiber Ion-Exchange Membrane Adsorption

Hsiu-Mei Chen, Peter J. Reilly, and Clark Ford, Iowa State University. Site-Directed Mutagenesis to Enhance Thermostability of Glucoamylase from Aspergillus: A Rational Approach

P. Tuitemwong, L. E. Erickson, and D. Y. C. Fung, Kansas State University. Applications of Enzymatic Hydrolysis and Fermentation on the Reduction of Flatulent Sugars in the Rapid Hydration Hydrothermal Cooked Soy Milk

Sanjeev Redkar and Robert H. Davis, University of Colorado. Crossflow Microfiltration of Yeast Suspensions

Linda Henk and James C. Linden, Colorado State University, and Irving C. Anderson, Iowa State University. Evaluation of Sorghum Ensilage as an Ethanol Feedstock

Marc Lipovitch and James C. Linden, Colorado State University. Stability and Biomass Feedstock Pretreatability for Simultaneous Saccharification and Fermentation

Ali Demirci, Anthony L. Pometto Ill, and Kenneth E. Johnson, Iowa State University. Application of Biofilm Reactors in Lactic Acid Fermentation

Michael K. Dowd, Peter I. Reilly, and WalterS. Trahanovsky, Iowa State University. Low Molecular-Weight Organic Composition of Ethanol Stillage from Corn

Craig E. Forney, Meng H. Heng, John R. Luther, Mark Q. Niederauer, and Charles E. Glatz, Iowa State University. Enhancement of Protein Separation Using Genetic Engineering

J. F. Shimp, J. C. Tracy, E. Lee, L. C. Davis, and L. E. Erickson, Kansas State University. Modeling Contaminant Transport, Biodegradation and Uptake by Plants in the Rhizosphere

Xiaoqing Yang, L. E. Erickson, and L. T. Fan, Kansas State University. Modeling of Dispersive-Convective Characteristics in Bioremediation of Contaminated Soil

Jan Johansson and Rakesh Bajpai, University of Missouri-Columbia. Fouling of Membranes

J. M. Wang, S. K. Banerji, and R. K. Bajpai, University of Missouri-Columbia. Migration of Sodium-Pentachorophenol (Na-PCP) in Unsaturated and Saturated Soil-Columns

J. Sweeney and M. Meagher, University of Nebraska-Lincoln. The Purification of Alpha-D-Glucuronidase from Trichoderma reesei

Eleven bacterial and two yeast strains, four of which were previously identified as having activity on a lightly cross-linked carboxymethyl cellulose (CLD-2) found in one type of superabsorbent tampon, were grown on a variety of substrates, most containing cellulosics. None produced detectable amounts of cellulases, but all elaborated beta-glucosidase. None of these 13 strains nor 3 commercially obtained beta-glucosidase preparations could hydrolyze CLD-2, although a commercial cellulase and two other bacterial preparations known to produce cellulases could. Based on these results, it appears that previous work suggesting that the degradation of CLD-2 by vaginal microbes and beta-glucosidase is implicated in the production by Staphylococcus aureus of toxin causing toxic shock syndrome must be reevaluated.

This the tenth in a series of symposia devoted to talks by students on their biochemical engineering research. The first, third, fifth, and ninth were at Kansas State University in Manhattan, the second and fourth were at the University of Nebraska–Lincoln, the sixth was in Kansas City in conjunction with the 81st American Institute of Chemical Engineers National Meeting, the seventh was at Iowa State University in Ames, and the eighth was held at the University of Missouri–Columbia.

Contents
"Combined Autohydrolysis-Organosolv Pretreatment of Lignocellulosic Materials," Robert A. Lewis, Colorado State University

"An Investigation of Cellulase Activity Assays," Minhhuong Nguyen, University of Missouri–Columbia

"Action Pattern of a Xylobiohydrolase from Aspergillus niger," Mary M. Frederick, Iowa State University

"Estimation of Heats of Combustion of Biomass from Elemental Analysis Using Available Electron Concepts," Snehal A. Patel, Kansas State University

"Design of a Wheat Straw to Ethanol Conversion Facility," Michael M. Meagher, Colorado State University

"Effects of Salt, Heat, and Physical Form on the Fermentation of Bananas," Carl Drewel, University of Missouri–Columbia

"Gas Hold-up in the Downflow Section of a Split Cylinder Airlift Column," Vasanti Deshpande, Kansas State University

"Measurement of Michaelis Constants for Soluble and Immobilized Glucoamylase," Robert A. Lesch, Iowa State University

"Kinetics of Alkaline Oxidation and Degradation of Sugars," Alfred R. Fratzke, Iowa State University

"Stability of Cereal Protein During Microbial Growth on Grain Dust," Bamidele O. Solomon, Kansas State University

Filtered stillage from the distillation of ethanol made by yeast fermentation of sugarcane molasses, citrus waste, and sweet whey was analyzed by gas chromatography/mass spectroscopy and by high-performance liquid chromatography. Nearly all of the major peaks representing low molecular weight organic components were identified. The major components in cane stillage were, in decreasing order of concentration, lactic acid, glycerol, ethanol, and acetic acid. In citrus stillage they were lactic acid, glycerol, myo-inositol, acetic acid, chiro-inositol, and proline. Finally, in whey stillage the major components were lactose, lactic acid, glycerol, acetic acid, glucose, arabinitol, and ribitol.

An endo-(l→4)-β-D-xylanase from a cellulase-free Chainia strain was substantially purified and subjected to amino acid sequencing. The first forty N-terminal amino acid residues show high homology with endo-xylanases from Bacillus pumilus, B. subtilis, B. circulans, andSchizophylum commune, less homology with endo-xylanases from Aureobasidium sp. andPseudomonas fluorescens, and slight homology, but including a possible catalytic Asp residue, with catalytic domains of endo-xylanases from Clostridium thermocellum,Cryptococcus albidus, and an alkalophilic Bacillus and with a cellobiohydrolase fromCellulomonas fimi. The enzyme attacks substrates as small as xylotetraose and has xylosyltransferase activity. It is most active at pH 6 and 60°C and most stable between pHs 5 and 7.

Dried and ensiled corn were each steeped with aqueous SO2 or water at initial pHs of 4-5; both were also steeped with aqueous SO2 at pH7. Initial steepwater composition or pH had less effect on yields of individual fractions and recoveries of various components than did differences between dried or ensiled corn. Recovery of starch after milling was appreciably higher with ensiled corn. Protein recovery in gluten decreased, but this was partially counterbalanced by increased protein content of the steepwater from ensiled corn. Results using batchwise steeping or a simulated countercurrent procedure were similar, though the latter gave higher starch recoveries.

Filtered stillage from the distillation of ethanol made by yeast fermentation of hydrolyzed corn starch was subjected to gas chromatography-mass spectroscopy and to high-performance liquid chromatography. Nearly all the major chromatographic peaks were identified and quantified. Low molecular weight organics in the soluble part of corn stillage were lactic acid, glycerol, and alanine, as well as smaller amounts of ethanol, and various nonnitrogenous and nitrogenous acids, polyhydroxy alcohols, sugars, and glucosides.

This is the seventeenth of a series of symposia devoted to talks by students about their biochemical engineering research. The first, third, fifth, ninth, twelfth, and sixteenth were at Kansas State University, the second and fourth were at the University of Nebraska-Lincoln, the sixth was in Kansas City and was hosted by Iowa State University, the seventh, tenth, thirteenth, and seventeenth were at Iowa State University, the eighth and fourteenth were at the University of Missouri–Columbia, and the eleventh and fifteenth were at Colorado State University. Next year's symposium will be at the University of Colorado. Symposium proceedings are edited by faculty of the host institution. Because final publication usually takes place elsewhere, papers here are brief, and often cover work in progress.

Contents
The Effect of Polymer Dosage Conditions on the Properties of ProteinPolyelectrolyte Precipitates, K. H. Clark and C. E. Glatz, Iowa State University

An Immobilized Enzyme Reactor/Separator for the Hydrolysis of Casein by Subtilisin Carlsberg, A. J. Bream, R. A. Yoshisato, and G. R. Carmichael, University of Iowa

Cell Density Measurements in Hollow Fiber Bioreactors, Thomas Blute, Colorado State University

The Hydrodynamics in an Air-Lift Reactor, Peter Sohn, George Y. Preckshot, and Rakesh K. Bajpai, University of Missouri–Columbia

Local Liquid Velocity Measurements in a Split Cylinder Airlift Column, G. Travis Jones, Kansas State University

Fluidized Bed Solid Substrate Trichoderma reesei Fermentation, S. Adisasmito, H. N. Karim, and R. P. Tengerdy, Colorado State University

The Effect of 2,4-D Concentration on the Growth of Streptanthus tortuosis Cells in Shake Flask and Air-Lift Permenter Culture, I. C. Kong, R. D. Sjolund, and R. A. Yoshisato, University of Iowa

Protein Engineering of Aspergillus niger Glucoamylase, Michael R. Sierks, Iowa State University

Structured Kinetic Modeling of Hybidoma Growth and Monoclonal Antibody Production in Suspension Cultures, Brian C. Batt and Dhinakar S. Kampala, University of Colorado

Modelling and Control of a Zymomonas mobilis Fermentation, John F. Kramer, M. N. Karim, and J. Linden, Colorado State University

Modeling of Brettanomyces clausenii Fermentation on Mixtures of Glucose and Cellobiose, Max T. Bynum and Dhinakar S. Kampala, University of Colorado, Karel Grohmann and Charles E. Yyman, Solar Energy Research Institute

Master Equation Modeling and Monte Carlo Simulation of Predator-Prey Interactions, R. 0. Fox, Y. Y. Huang, and L. T. Fan, Kansas State University

Kinetics and Equilibria of Condensation Reactions Between Two Different Monosaccharides Catalyzed by Aspergillus niger Glucoamylase, Sabine Pestlin, Iowa State University

Biodegradation of Metalworking Fluids, S. M. Lee, Ayush Gupta, L. E. Erickson, and L. T. Fan, Kansas State University

Redox Potential, Toxicity and Oscillations in Solvent Fermentations, Kim Joong, Rakesh Bajpai, and Eugene L. Iannotti, University of Missouri–Columbia

Using Structured Kinetic Models for Analyzing Instability in Recombinant Bacterial Cultures, William E. Bentley and Dhinakar S. Kompala, University of Colorado

The symposium reported here was the thirteenth of a series devoted to talks by students on their biochemical engineering research. The first, third, fifth, ninth, and twelfth were at Kansas State University, the second and fourth were at the University of Nebraska–Lincoln, the sixth was in Kansas City and was hosted by Iowa State University, the seventh and tenth were at Iowa State, and the eighth and eleventh were at the University of Missouri–Columbia and Colorado State University, respectively. All symposia have been followed by proceedings edited by faculty of the host institution. Because final publication usually takes place elsewhere, papers here are brief, and often cover research in progress.

Content
Sequential Utilization of Mixed Sugars by Clostridium acetobutylicum, B. Hong, N. H. Choi, and L. T. Fan, Kansas State University

The Effects of Dilution Rate on the Kinetics. of Anaerobic Acidogenesis, C. J. Huang, Colorado State University

Ethanol Production by Zymomonas mobilis in Anaerobic Glucose-Limited Culture: A Yield Study, Mehmet D. Oner, Kansas State University

Hydrolysis of Cellulosics by Enterobacteria, Michael R. Sierks, Iowa State University

The Cellulase System of Chaetomium cellulolyticum, Nikhil Mehta, Colorado State University

DNA Measurement as a Tool for Estimating Biomass Concentration in the Presence of Interfering Solids, Bamidele 0. Solomon, Kansas State University

The Effect of Cellulose Crystallinity on Enzymatic Hydrolysis, Maria S. Bertran, Colorado State University

High Performance Liquid Chromatography of Di- and Trisaccharides, Michael M. Meagher, Iowa State University

Dynamics of Bubble Size .Distributions in Air-Lift Fermentors, c. H. Lee and Snehal A. Patel, Kansas State University

A Thermal Coagulation Study of Alfalfa Leaf Proteins by Differential Scanning Calorimeter, Khalif Ahmed and Bruce Dale, Colorado State University

Thermodynamic Efficiency of Photoautotrophic Growth, Hyeon Y. Lee, Kansas State University