Corliss A. O’Bryan

Escherichia coli, an Intestinal Microorganism, as a Biosensor for Quantification of Amino Acid Bioavailability

In animal diets optimal amino acid quantities and balance among amino acids is of great nutritional importance. Essential amino acid deficiencies have negative impacts on animal physiology, most often expressed in sub-optimal body weight gains. Over supplementation of diets with amino acids is costly and can increase the nitrogen emissions from animals. Although in vivo animal assays for quantification of amino acid bioavailability are well established, Escherichia coli-based bioassays are viable potential alternatives in terms of accuracy, cost, and time input. E. coli inhabits the gastrointestinal tract and although more abundant in colon, a relatively high titer of E. coli can also be isolated from the small intestine, where primary absorption of amino acids and peptides occur. After feed proteins are digested, liberated amino acids and small peptides are assimilated by both the small intestine and E. coli. The similar pattern of uptake is a necessary prerequisite to establish E. coli cells as accurate amino acid biosensors. In fact, amino acid transporters in both intestinal and E. coli cells are stereospecific, delivering only the respective biological l-forms. The presence of free amino- and carboxyl groups is critical for amino acid and dipeptide transport in both biological subjects. Di-, tri- and tetrapeptides can enter enterocytes; likewise only di-, tri- and tetrapeptides support E. coli growth. These similarities in addition to the well known bacterial genetics make E. coli an optimal bioassay microorganism for the assessment of nutritionally available amino acids in feeds.

Marketing Locally Produced Organic Foods in Three Metropolitan Arkansas Farmers’ Markets: Consumer Opinions and Food Safety Concerns

Consumers embrace local food systems as an alternative to the global corporate model, and nearly 75% of consumers in the United States purchase organic foods occasionally. To assess consumers’ knowledge of locally grown organic foods, surveys were administered at three metropolitan farmers’ markets in Little Rock, Hot Springs, and Texarkana, Arkansas. Consumers with Bachelors, Associates, or technical degrees accounted for almost half of the people surveyed. Seventy-one percent believed organic foods were safer than conventional foods. Three times as many consumers were concerned about harmful bacteria in conventional foods than in organic. The number one reason for purchasing was to support local farmers.

The Role of Prebiotics and Probiotics in Human Health

There has recently been a significant increase in research on the potential health benefi ts associated with probiotics and prebiotics. Some effects attributed to selected probiotics or prebiotics have been proved by clinical trials, while others have been acquired on the basis of in vitro tests which need to be replicated in vivo in order to be validated. Clinical reports in the literature for the application of probiotics have been done for the treatment of infectious diseases including viral, bacterial or antibiotic associated diarrhea, lowering of serum cholesterol, decreased risk of colon cancer, improved lactose digestion, and altered intestinal microbiota. However, information on probiotic species, a specific strain-therapeutic application, and adequate dosages, is not yet sufficient to allow rational consumption. Moreover, prebiotic oligosaccharides are poorly understood in regard to their fermentation profi les and dosages required for health effects. The present review summarizes some of the literature in regard to clinical or therapeutic trials of probiotics and prebiotics.

Alternative antimicrobial compounds to control potential Lactobacillus contamination in bioethanol fermentations.

Antibiotics are commonly used to control microbial contaminants in yeast-based bioethanol fermentation. Given the increase in antibiotic-resistant bacteria, alternative natural antimicrobials were evaluated against the potential contaminant, Lactobacillus. The effects of nisin, ϵ-polylysine, chitosan (CS) and lysozyme were screened against 5 Lactobacillus strains. A standard broth- microdilution method was used in 96-well plates to assess the minimal inhibitory concentration (MIC). L. delbrueckii subsp lactis ATCC479 exhibited maximal MICs with CS, ϵ-polylysine and nisin (1.87, 0.3125 and 0.05 mg/mL, respectively). Nisin reduced most Lactobacillus strains by 6 log CFU/mL after 48 hours with the exception of L. casei. Synergism occurred when ethylenediaminetetraacetic acid (EDTA) was added with nisin. An MIC of 0.4 mg/mL of nisin combined with the EDTA at an MIC of 1 mg/ml markedly suppressed L .casei by 6 log CFU/mL. In conclusion, alternative antimicrobials proved to be a potential candidate for controlling bacterial contamination in the fermentation process. Synergistic effect of nisin with EDTA successfully inhibited the nisin-resistant contaminant, L. casei.

Estimating the Demand for Organic Foods by Consumers at Farmers’ Markets in Northwest Arkansas

To answer the question, “How interested in buying organic foods are the majority of the current shoppers at our farmers’ market?,” more than 300 consumers at three diverse farmers’ market locations were surveyed for their organic food purchasing habits. Comparisons were made between purchasers who were new to purchasing organic foods and purchasers who had been buying organic foods for many years. Analysis showed that a majority of respondents (74%) were frequent purchasers of organic foods, buying once or twice a month and a significant percentage (44%) of those had been purchasing organic foods for 7 years or more. Opportunities exist to expand organic sales at these farmers’ markets in Arkansas, where only 42% purchased most of their organic foods and 80% surveyed answered “yes” that they would buy more organic if its price was similar to that of conventional foods.

Potential of Plant Essential Oils and Their Components in Animal Agriculture – in vitro Studies on Antibacterial Mode of Action

The antimicrobial activity of essential oils and their components has been recognized for several years. Essential oils are produced as secondary metabolites by many plants and can be distilled from all different portions of plants. The recent emergence of bacteria resistant to multiple antibiotics has spurred research into the use of essential oils as alternatives. Recent research has demonstrated that many of these essential oils have beneficial effects for livestock, including reduction of foodborne pathogens in these animals. Numerous studies have been made into the mode of action of essential oils, and the resulting elucidation of bacterial cell targets has contributed to new perspectives on countering antimicrobial resistance and pathogenicity of these bacteria. In this review, an overview of the current knowledge about the antibacterial mode of action of essential oils and their constituents is provided.

Antimicrobial properties of three lactic acid bacterial cultures and their cell free supernatants against Listeria monocytogenes

Control of Listeria monocytogenes in ready-to-eat (RTE) food products is a significant challenge and improved means for control are needed. In this study, the anti-listerial effects of three lactic acid bacteria (LAB) were investigated. Spot-on-lawn assays demonstrated the largest zones of inhibition against L. monocytogenes were produced by the Pediococcus acidilactici strain, with zone diameters ranging from 13 to 18 mm. Minimum inhibitory concentration (MIC) experiments using cell free supernatant (CFS) from the LAB revealed that while two of the strains were effective at inhibiting L. monocytogenes growth only up to a 1:4 dilution, P. acidilactici was able to inhibit growth up to a 1:256 dilution. Survival assays performed at 7°C determined that the P. acidilactici strain was capable of producing a 4.5 log reduction in L. monocytogenes counts and maintaining the reduction for 21 days. The effectiveness of P. acidilactici was reduced under log phase growth, autoclaving for longer than 15 min (121°C and 15 psi), and treatment with proteinase K (25 mg/mL).

Possibility for Probiotic Sources of Methionine for Organic Poultry Nutritional Supplementation: An Early Review

Methionine is a nutritionally essential amino acid required in the diet of humans and livestock, including poultry. Chickens are unable to produce methionine and therefore must obtain it through their diets. Generally, methionine is one of the first limiting amino acids in poultry nutrition and typically in most diets this amino acid has to be added to the poultry feed. Currently, methionine is produced by chemical processes or hydrolyzing proteins. However, chemical synthesis is expensive and produces a mixture of D- and L-methionine. In addition, these sources of amino acids are problematic as nutritional supplements for organic poultry production. It may be possible to develop microbial sources of methionine that would meet the criteria for organic use but since genetic modification is not allowed this will require isolation of naturally occurring methionine over-producers. Application of such cultures may work as external sources of pure methionine but it may be more cost effective to develop a probiotic approach either by directly administering such cultures or enriching for members of the gastrointestinal population already present that have this ability. This review discusses these strategies and the criteria required to meet the requirements for methionine supplementation in these production systems.

Cleaning and decontamination efficacy of wiping cloths and silver dihydrogen citrate on food contact surfaces

Aims:  To test the efficacy of four wipe cloth types (cotton bar towel, nonwoven, microfibre and blended cellulose/cotton) with either quaternary ammonia cleaning solution or silver dihydrogen citrate (SDC) in cleaning food contact surfaces.

The Potential Link between Thermal Resistance and Virulence in Salmonella: A Review

In some animals, the typical body temperature can be higher than humans, for example, 42°C in poultry and 40°C in rabbits which can be a potential thermal stress challenge for pathogens. Even in animals with lower body temperatures, when infection occurs, the immune system may increase body temperature to reduce the chance of survival for pathogens. However, some pathogens can still easily overcome higher body temperatures and/or rise in body temperatures through expression of stress response mechanisms. Salmonella is the causative agent of one of the most prevalent foodborne illnesses, salmonellosis, and can readily survive over a wide range of temperatures due to the efficient expression of the heat (thermal) stress response. Therefore, thermal resistance mechanisms can provide cross protection against other stresses including the non-specific host defenses found within the human body thus increasing pathogenic potential. Understanding the molecular mechanisms associated with thermal responses in Salmonella is crucial in designing and developing more effective or new treatments for reducing and eliminating infection caused by Salmonella that have survived heat stress. In this review, Salmonella thermal resistance is assessed followed by an overview of the thermal stress responses with a focus on gene regulation by sigma factors, heat shock proteins, along with the corresponding thermosensors and their association with virulence expression including a focus on a potential link between heat resistance and potential for infection.