Food Science Commons^™

Membrane Topology Of The Colicin A Pore-Forming Domain Analyzed By Disulfide Bond Engineering, Denis Duche, Jacques Izard, Juan M. Gonzalez-Manas, Michael W. Parker, Marcel Crest, Daniel Baty

Department of Food Science and Technology: Faculty Publications

Four colicin A double-cysteine mutants possessing a disulfide bond in their pore-forming domain were constructed to study the translocation and the pore formation of colicin A. The disulfide bonds connected a-helices 1 and 2, 2 and 10, 3 and 9, or 3 and 10 of the poreforming domain. The disulfide bonds did not prevent the colicin A translocation through the Escherichia coli envelope. However, the mutated colicins were able to exert their in vivo channel activity only after reduction of their disulfide bonds. In vitro studies with brominated phospholipid vesicles and planar lipid bilayers revealed that the disulfide bond that …

A Sandwich Enzyme-Linked Immunosorbent Assay (Elisa) For The Quantitation Of Peanut In Foods, S. L. Taylor, Julie A. Nordlee, S. L. Hefle

Department of Food Science and Technology: Faculty Publications

Peanuts are one of the most allergenic foods known. Strict avoidance of peanut by peanut-allergic individuals is difficult and often unsuccessful. Peanut proteins have previously been found in nonpeanut foodstuffs prepared on shared processing equipment, and such carryover contamination increases the risk of occurrence of allergic reactions. Immunoassays offer a specific, sensitive, and rapid technique to detect and quantitate small amounts of proteins in food systems.

A sandwich-type, enzyme-linked immunosorbent assay (ELISA) was developed for the detection of peanut protein in foods. Selected food samples were ground and extracts prepared by overnight extraction in 0.01 M phosphate buffered saline, followed …

Allergenic Foods, Susan L. Hefle, Julie A. Nordlee, Steve L. Taylor

Department of Food Science and Technology: Faculty Publications

Virtually all food allergens are proteins, although only a small percentage of the many proteins in foods are allergens. Any food that contains protein has the potential to cause allergic reactions in some individuals. However, a few foods or food groups are known to cause allergies on a more frequent basis than other foods. At a 1995 consultation on food allergies sponsored by the Food and Agriculture Organization, a group of international experts confirmed that peanuts, soybeans, crustacea, fish, cow’s milk, eggs, tree nuts, and wheat are the most common allergenic foods. These foods are responsible for more than 90% …

Cloning And Characterization Of The Galactokinase Gene From Streptococcus Thermophilus, Azlin Mustapha, Robert W. Hutkins, Gerald W. Hirnstein

Department of Food Science and Technology: Faculty Publications

The objective of this research was to clone and characterize the galactokinase gene (gal0 from Streptococcus therrnophilus F4 10. Partially digested genomic DNA was cloned into pBR322 and transformed into galK Escherichia coli, and a galactose-fermenting transformant was isolated. Restriction analysis revealed that the transformant resulted from a Sau3A-HindIIl 4.0-kb fragment. Galactokinase activity in the recombinant was 10 times that of the parent strain. Analysis of the DNA squence showed the presence of a 1.3-kb open reading frame that had high homology with the galK gene from other organisms. A putative ribosome-binding site, start and stop codons, and -10 …

Global Regulation Of A Σ54-Dependent Flagellar Gene Family In Caulobacter Crescentus By The Transcriptional Activator Flbd, Jianguo Wu, Andrew K. Benson, Austin Newton

Department of Food Science and Technology: Faculty Publications

Biosynthesis of the Caulobacter crescentus polar flagellum requires the expression of a large number of flagellar (fla) genes that are organized in a regulatory hierarchy of four classes (I to IV). The timing of fla gene expression in the cell cycle is determined by specialized forms of RNA polymerase and the appearance and/or activation of regulatory proteins. Here we report an investigation of the role of the C. crescentus transcriptional regulatory protein FlbD in the activation of σ⁵⁴-dependent class III and class IV fla genes of the hierarchy by reconstituting transcription from these promoters in vitro. …

Glucose Uptake By Listeria Monocytogenes Scott A And Inhibition By Pediocin Jd, Douglas P. Christensen, Robert W. Hutkins

Department of Food Science and Technology: Faculty Publications

Glucose uptake by Listeria monocytogenes Scott A was inhibited by the bacteriocin pediocin JD and by the protonophore carbonyl cyanide m-chlorophenyhydrazone. Experiments with monensin, nigericin, chlorhexidine diacetate, dinitrophenol, and gramicidin, however, showed that glucose uptake could occur in the absence of a proton motive force. L. monocytogenes cell extracts phosphorylated glucose when phosphoenolpyruvate (PEP) was present in the assay mixture, and whole cells incubated with 2-deoxyglucose accumulated 2-deoxyglucose-6-phosphate, indicating the presence of a PEP-dependent phosphotransferase system in this organism. Glucose phosphorylation also occurred when ATP was present, suggesting that a proton motive force-mediated glucose transport system may also be …

Browning Of Mozzarella Cheese During High Temperature Pizza Baking, Beatriz Matzdorf, Susan L. Cuppett, Laurie J. Keeler, Robert W. Hutkins

Department of Food Science and Technology: Faculty Publications

The objective of this study was to evaluate various properties of low browning Mozzarella cheese. Low moisture, part skim type Mozzarella cheese was made using strains of Streptococcus spp. and Lactobacillus helveticus that release inappreciable amounts of galactose into the cheese curd and was compared with high browning cheese made using cultures that release galactose into the curd. Cheese composition differed only for galactose content. The browning potentials of the cheeses were significantly different. Pizzas were made using 125 g of each cheese type and evaluated for appearance, texture, and flavor by a consumer panel. Panelists could distinguish between pizza …

Isolation Of Galactose-Fermenting Thermophilic Cultures And Their Use In The Manufacture Of Low Browning Mozzarella Cheese, Kamla K. Mukhurjee, Robert W. Hutkins

Department of Food Science and Technology: Faculty Publications

The objectives of this study were to isolate galactose-fermenting, galactosenonreleasing strains of Streptococcus and Lactobacillus and to use these strains as starter cultures in the manufacture of low browning Mozzarella cheese. Four Streptococcus isolates having the desirable phenotype, combined with a Lactobacillus helveticus strain, were acceptable as starter cultures based on activity tests. Fifteen vats of Mozzarella cheese were produced, in triplicate, representing four experimental treatments (made with galactose-nonreleasing strains) and one control (made with a galactosefermenting, galactose-releasing Streptococcus). Analyses were performed on cheese after 5 and 28 d of refrigerated storage. The lactose and galactose content of cheese …

The Caulobacter Crescentus Flbd Protein Acts At Ftr Sequence Elements Both To Activate And To Repress Transcription Of Cell Cycle-Regulated Flagellar Genes, Andrew K. Benson, Girija Ramakrishnan, Noriko Ohta, Junli Feng, Alexander J. Ninfa, Austin Newton

Department of Food Science and Technology: Faculty Publications

The flagellar genes (fla genes) in Caulobacter crescentus are categorized into a regulatory hierarchy of four levels, I-IV, in which transcription of the class III and class IV genes late in the cell cycle from σ⁵⁴-dependent promoters depends on expression of the class II genes above them. Timing of fla gene expression has been attributed to sequential activation and repression by specific transcription factors. Here we report that purified FlbD activates transcription in vitro from the σ⁵⁴-dependent class III flbG promoter and represses transcription from the class II fliF promoter by binding to ftr (flagellar …

Ph Homeostasis In Lactic Acid Bacteria, Robert W. Hutkins, Nancy L. Nannen

Department of Food Science and Technology: Faculty Publications

The ability of lactic acid bacteria to regulate their cytoplasmic or intracellular pH is one of the most important physiological requirements of the cells. Cells unable to maintain a near neutral intracellular pH during growth or storage at low extracellular pH may lose viability and cellular activity. Despite the importance of pH homeostasis in the lactic acid bacteria, however, an understanding of cytoplasmic pH regulation has only recently begun to emerge. This review describes the specific effects of low pH on lactic acid bacteria, reports recent research on the physiological role of intracellular pH as a regulator of various metabolic …

United States Patent: Composition And Method For Inhibiting Pathogens And Spoilage Organisms In Food, Robert W. Hutkins, Elaine D. Berry, Michael B. Liewen

Department of Food Science and Technology: Faculty Publications

The method of the invention uses live cells of non-fermenting and/or non-growing lactic acid bacteria to deliver bacteriocin into edible food substances to inhibit the growth of food spoilage and/or food-borne pathogenic organisms. The method of the invention may be used to inhibit growth of these organisms in raw food substances and finished food products after processing. The lactic acid bacteria within the food mixture are capable of producing bacteriocin in the desired microbial- inhibiting amounts under conditions of non-growth and non-fermentation

Regulation Of ΣB Levels And Activity In Bacillus Subtilis, Andrew K. Benson, William G. Haldenwang

Department of Food Science and Technology: Faculty Publications

The sigB operon of Bacilus subtilis encodes (σ^B plus three additional proteins (RsbV, RsbW, and RsbX) that regulate σ^B activity. Using an anti-σ^B monoclonal antibody to monitor the levels of (σ^B protein, P_SPAC to control the expression of the sigB operon, and a ctc-lacZ reporter system to monitor σ^B activity, we observed that the rsbV and rsbW products control (σ^B activity at the ctc promoter independently of their effects on (σ^B levels. In contrast, RsbX was found to have no effect on expression of ctc when the sigB operon was controlled by …

Bacillus Subtilis ΣB Is Regulated By A Binding Protein (Rsbw) That Blocks Its Association With Core Rna Polymerase, Andrew K. Benson, William G. Haldenwang

Department of Food Science and Technology: Faculty Publications

σ^B is a secondary σ factor of Bacillus subtilis. RNA polymerase containing cr transcribes a subset of genes that are expressed after heat shock or the onset of the stationary phase of growth. Three genes (rsbV, rsbW, and rsbX), cotranscribed with the σ^B structural gene (sigB), regulate o dependent gene expression. RsbW is the primary inhibitor of this system with the other gene products acting upstream of RsbW in the σ^B regulatory pathway. Evidence is now presented that RsbW inhibits σ^B-dependent transcription by binding to crB and blocking …

The ΣB-Dependent Promoter Of The Bacillus Subtilis Sigb Operon Is Induced By Heat Shock, Andrew K. Benson, W. G. Haldenwang

Department of Food Science and Technology: Faculty Publications

σ^B, a secondary sigma factor of Bacillus subtilis, was found to increase 5- to 10-fold when cultures were shifted from 37 to 48°C. Western blot (immunoblot) analyses, in which monoclonal antibodies specific for the sigB operon products RsbV, RsbW, and σ^B were used to probe extracts from wild-type and mutant B. subtilis strains, revealed that all three proteins increased coordinately after heat shock and that this increase was dependent on σ^B but not RsbV, a positive regulator normally essential for σ^B-dependent sigB expression. Nuclease protection experiments of RNA synthesized after heat shock supported …

Collapse Of The Proton Motive Force In Listeria Monocytogenes Caused By A Bacteriocin Produced By Pediococcus Acidilactici, Douglas P. Christensen, Robert W. Hutkins

Department of Food Science and Technology: Faculty Publications

The effect of pediocin JD, a bacteriocin produced by Pediococcus acidilactici JD1-23, on the proton motive force and proton permeability of resting whole cells of Listeria monocytogenes Scott A was determined. Control cells, treated with trypsin-inactivated bacteriocin at a pH of 5.3 to 6.1, maintained a pH gradient and a membrane potential of approximately 0.65 pH unit and 75 mV, respectively. However, these gradients were rapidly dissipated in cells after exposure to pediocin JD, even though no cell lysis had occurred. The pH gradient and membrane potential of the producer cells were also unaffected by the bacteriocin. Whole cells treated …

Characterization Of A Regulatory Network That Controls ΣB Expression In Bacillus Subtilis, Andrew K. Benson, William G. Haldenwang

Department of Food Science and Technology: Faculty Publications

The sigB operon of Bacillus subtilis encodes σ^B and three additional open reading frames (orfV, orfW, and orfX). Having previously mapped several mutations that alter the induction pattern of a σ^B-dependent promoter (ctc) to regions of cloned B. subtilis DNA which contain these three open reading frames, we directly tested the regulatory potential of orfV, orfW, and orfX by creating null alleles of each of these genes and examining the effects of the mutations, either singly or in pairs, on transcription of ctc and the sigB operon. …

Intracellular Ph Effects In Lactic Acid Bacteria, Nancy L. Nannen, Robert W. Hutkins

Department of Food Science and Technology: Faculty Publications

The objectives of this research were to determine the effect of lactic acid and low pH on the intracellular pH in three species of lactic acid bacteria. A pH gradient (intracellular pH minus the extracellular pH) of .9 to 1.4 pH units was achieved by several strains of lactic acid bacteria, including Streptococcus thermophilus 19258 and 573, Lactococcus lactis ssp. lactis C2, and Lactococcus lactis ssp. cremoris HP during log phase of growth in various media. A noticeable decline of the pH gradient occurred at an internal pH of 5.5 to 6.0. In late stationary phase, the pH gradient was …

Proton-Translocating Adenosine Triphosphatase Activity In Lactic Acid Bacteria, Nancy L. Nannen, Robert W. Hutkins

Department of Food Science and Technology: Faculty Publications

Streptococcus thermophilus 19258 and 573, Luctococcus luctis ssp. lucris C2, Lactococcus luctis ssp. cremoris HP, and Luctobucillus cusei 685 were grown in various media and assayed for protontranslocating ATPase (H⁺-ATPase) activity. The H⁺-ATPase was extracted from the membrane fractions of protoplasted cells using a French pressure cell, and activity was measured by the release of inorganic phosphate from ATP. The pH optima for the H⁺-ATPase, assayed in vitro, were 7.5 for S. thermophilus and Lactococcus luctis ssp. cremoris HP and 5.0 for Lactobacillus casei 685. In contrast, for cells grown in batch …

Lactose Uptake Driven By Galactose Efflux In Streptococcus Thermophilus: Evidence For A Galactose-Lactose Antiporter, Robert W. Hutkins, Carina Ponne

Department of Food Science and Technology: Faculty Publications

Galactose-nonfermenting (Gal^-) Streptococcus thermophilus TS2 releases galactose into the extracellular medium when grown in medium containing excess lactose. Starved and de-energized Gal^- cells, however, could be loaded with galactose to levels approximately equal to the extracellular concentration (0 to 50 mM). When loaded cells were separated from the medium and re-suspended in fresh broth containing 5 mM lactose, galactose efflux occurred. De-energized, galactose-loaded cells, re-suspended in buffer or medium, accumulated ['4C]lactose at a greater rate and to significantly higher intracellular concentrations than unloaded cells. Uptake of lactose by loaded cells was inhibited more than that by unloaded …

Function Of Preliminary Incubation Of Raw Milk Samples For Quality Control, R. Burt Maxcy, Michael Liewen

Department of Food Science and Technology: Faculty Publications

Preliminary incubation of raw milk samples to evaluate bacterial quality has been a commonly recommended practice. The presumption has been that selective growth of a segment of the microflora associated with unsanitary methods and conditions would be enhanced. The present work involved a theoretical approach to evaluate this presumption. Pure cultures of Pseudomonas aeruginosa, P. fluorescens, and Escherichia coli as well as enriched mixed cultures of psychrotrophs and mesophiles were used. The generation time of each culture was determined at various temperatures. An analysis of covariance showed the coefficients of generation time related to temperature were not significantly different. …

Sensitivity To Sulfited Foods Among Sulfite-Sensitive Subjects With Asthma, Steve L. Taylor, Robert K. Bush, John C. Selner, Julie A. Nordlee, Matthew B. Wiener, Karen Holden, Jerald W. Koepke, William W. Busse

Department of Food Science and Technology: Faculty Publications

Eight individuals with asthma who had been diagnosed as sulfite sensitive on the basis of double-blind capsule-beverage challenges were subjected to challenges with various sulfited foods, including lettuce, shrimp, dried apricots, white grape juice, dehydrated potatoes (as mashed potatoes), and mushrooms. Four of these patients failed to respond to challenges with any of the sulfited foods. The other four patients experienced a decrease in pulmonary function on double-blind challenges with sulfited lettuce. Two of three of these patients reacted to challenges with dried apricots and white grape juice; the fourth patient has not yet been challenged with these products. Only …

Sensitivity To Ingested Sulfites, Steve L. Taylor, Julie A. Nordlee

Department of Food Science and Technology: Faculty Publications

Sulfiting agents, including sodium and potassium bisulfite, sodium and potassium metabisulfite, sodium sulfite, and sulfur dioxide, have enjoyed widespread use as food and drug ingredients. The oral ingestion of these sulfiting agents is now known to trigger asthma in a small subset of the asthmatic population. The best evidence suggests that perhaps 150,000 to 200,000 individuals in the United States may be sulfite sensitive. Although the mechanism of sulfite-induced asthma remains unknown, several possibilities have been considered, including inhalation of sulfur dioxide (SO₂) while swallowing, an IgE-mediated reaction, and a deficiency of sulfite oxidase leading to impaired sulfite …

Betaine Transport Imparts Osmotolerance On A Strain Of Lactobacillus Acidophilus, Robert W. Hutkins, William L. Ellefson, Eva R. Kashket

Department of Food Science and Technology: Faculty Publications

Unlike most Lactobacilus acidophilus strains, a specific strain, L. acidophilus IF0 3532, was found to grow in rich medium containing 1 M sodium acetate, KCI, or NaCl. This strain could also grow with up to 1.8 M NaCl or 3 M nonelectrolytes (fructose, xylose, or sorbitol) added. Thus, this strain was tolerant to osmotic pressures up to 2.8 osM. A search for an intracellular solute which conferred osmoprotection led to the identification of glycine betaine (betaine). Betaine was accumulated to high concentrations in cells growing in MRS medium supplemented with 1 M KCI or NaCl. Uptake of [¹⁴C]betaine …

Food Quality And Energy Usage In Foodservice Systems: Convective Thermal Processing Of Turkey Rolls, M. E. Matthews, M. E. Zabik, R. B. Maxcy

Department of Food Science and Technology: Faculty Publications

This study evaluated sensory and nutritional qualities, microbioloqical and chemical safety of turkey rolls and enerqy use durinq convective thermal processing. Turkey rolls were heat processed in home or institutional convection ovens to an internal temperature of 77 to 80°C in the geometric center of the roll. Treatment combinations included three heat-processing temperatures (105, 135, and 165°C) and two holding treatments (not chilled and chilled for 24 hr) and three hot-holding times (0, 60 and 120 min). Sensory studies of white turkey meat roasted at 165°C and reheated showed that juiciness decreased significantly (p<0.05), compared to roasting at 105 or 135°C without reheating. Juiciness was also decreased significantly (p<0.05) as hot-holding progressed (0 to 120 min).

Coagglutination And Enzyme Capture Tests For Detection Of Escherichia Coli Β-Galactosidase, Β-Glucuronidase, And Glutamate Decarboxylase, Charles W. Kaspar, Paul A. Hartman, Andrew K. Benson

Department of Food Science and Technology: Faculty Publications

Polyclonal antibodies to Escherichia coli β-galactosidase, β-glucuronidase, and glutamate decarboxylase were used in coagglutination tests for identification of these three enzymes in cell lysates. Enzyme capture assays were also developed for the detection of E. coli β-galactosidase and β-glucuronidase. The enzymes were released by using a gentle lysis procedure that did not interfere with antibody-enzyme interactions. All three enzymes were detected in 93% (51 of 55) of the E. coli strains tested by coagglutination; two of the three enzymes were identified in the remaining 7%. Of 42 non-E. coli tested by coagglutination, only four nonspecifically agglutinated either two or …

Prevalence Of Sensitivity To Sulfiting Agents In Asthmatic Patients, Robert K. Bush, Steve L. Taylor, Karen Holden, Julie A. Nordlee, William S. Busse

Department of Food Science and Technology: Faculty Publications

Ingestion of sulfiting agents can induce wheezing in some asthmatic patients. However, neither the prevalence of sulfite sensitivity nor the clinical characteristics of the affected asthmatic population are known. In a prospective single-blind screening study, 120 non-steroid-dependent and 83 steroid-dependent asthmatic patients underwent challenge with oral capsules of potassium metabisulfite. Five non-steroid-dependent and 16 steroid-dependent asthmatic patients experienced a greater than 20 percent reduction in their one-second forced expiratory volume within 30 minutes following the oral challenge. Twelve of these sulfite reactors were rechallenged with metabisulfite capsules in a double-blind protocol. Under these conditions, only three of seven steroid-dependent patients …

Phosphotransferase Activity In Clostridium Acetobutylicum From Acidogenic And Solventogenic Phases Of Growth, Robert W. Hutkins, Eva R. Kashket

Department of Food Science and Technology: Faculty Publications

Clostridium acetobutylicum cells, when energized with fructose, transported and phosphorylated the glucose analog 2-deoxyglucose by a phosphoenolpyruvate-dependent phosphotransferase (PT) system. Butanol up to 2% did not inhibit PT activity, although its chaotropic effect on the cell membrane caused cellular phosphoenolpyruvate and the 2-deoxyglucose-6-phosphate to leak out. Cells harvested from the solventogenic phase of batch growth had a significantly lower PT activity than did cells from the acidogenic phase.

Use Of Galactose-Fermenting Streptococcus Thermophilus In The Manufacture Of Swiss, Mozzarella, And Short-Method Cheddar Cheese, Robert W. Hutkins, S.M. Halambeck, H.A. Morris

Department of Food Science and Technology: Faculty Publications

Galactose-fermenting (galactose-posirive) strains of Streptococcus tbermopbilus, alone and combined with galactosepositive and galactose-negative strains of Lactobacillus bulgaricus, were used as starter cultures in the manufacture of Swiss and Mozzarella cheese and were paired with Streptococcus lactis (also galactose-positive) in short-method Cheddar cheese manufacture. Experimental Swiss cheese made with the galactosepositive Streptococcus tbermopbilus starter alone contained a large amount of galactose (ca. 26 to 28 /amol/g of curd) 28 h after hooping compared with control Swiss (< 2/amol/g) made with a nongalactose fermenting strain of Streptococcus tbermopbilus and a galactosepositive strain of Lactobacillus bulgaricus. Mozzarella and short-method Cheddar made with only galactose-positive Streptococcus tbermopbilus also contained …

Simple Method To Demonstrate Radiation-Inducible Radiation Resistance In Microbial Cells, S. T. Tan, R. B. Maxcy

Department of Food Science and Technology: Faculty Publications

A simple method for detection of radiation-inducible radiation resistance was developed by irradiating aliquots (0.01 ml) of cell suspension on agar plates. Part of each experimental plate was subjected to an induction treatment, and subsequent radiation resistance was compared with that of untreated cells on the same plate. The UV radiation resistance of a Micrococcus sp. was increased approximately 1.6 times by an induction treatment. This simple procedure of irradiating cells in a "fixed" position on agar avoided washing, centrifugation, and cell enumeration required in traditional methods.

Galactokinase Activity In Streptococcus Thermophilus, Robert W. Hutkins, Howard A. Morris, Larry L. Mckay

Department of Food Science and Technology: Faculty Publications

ATP-dependent phosphorylation of [¹⁴Cigalactose by 11 strains of Streptococcus thermophilus indicated that these organisms possessed the Leloir enzyme, galactokinase (galK). Activities were 10 times higher in fully induced, galactose-fermenting (Gal⁺) strains than in galactose-nonfermenting (Gal-) strains. Lactose-grown, Gal^- cells released free galactose into the medium and were unable to utilize residual galactose or to induce galK above basal levels. Gal⁺ S. thermophilus 19258 also released galactose into the medium, but when lactose was depleted growth on galactose commenced, and galK increased from 0.025 to 0.22 μmol of galactose phosphorylated per min per mg of …