Development of antimicrobial coatings for improving the microbiological safety and quality of shell eggs

Novel Fabrication of Bio-polymeric Nanogel Loaded with Nalidixic Acid Formulations for the Effective Prevention of Bacterial Pathogens Leading Urinary Tract Infection and Its Biosafety Evaluation

Management of urinary tract infections (UTI) is a highly challenging process due to the biofilm-forming ability of human-pathogenic bacteria. Here, we designed to fabricate an effective nanogel with a combination of chitosan bio-polymer and nalidixic acid to prevent biofilm-forming bacterial pathogens. Chitosan-coated nalidixic acid nanogel (NA@CS) exhibits outstanding inhibition potential against bacterial strains. In vitro, anti-bacterial analysis methods (well diffusion, colony-forming assay, and anti-biofilm assay) were performed to study the bacterial inhibition potential of prepared nanogel, which reveals that NA@CS nanogel have greater inhibition potential against selected pathogens. The combination of nalidixic acid with chitosan biopolymer decreases the virulence and pathogenicity of biofilm-forming pathogens due to their ability to membrane phospholipids penetration. Furthermore, the fabricated NA@CS nanogel showed reliable in vitro bio-compatibility on L929 fibroblast cells and in vivo compatibility with Artemia salina animal model. Overall, the results demonstrate that NA@CS nanogel could be an effective therapeutic for treating urinary tract infections and urine bladder wound healing.

Efficacy of pectin-based caproic acid, caprylic acid, linalool, and cuminaldehyde coatings in reducing Salmonella Heidelberg on chicken eggs

Among the animal derived food products, contamination of poultry eggs, and egg shell surface is one of the major causes for foodborne salmonellosis in the United States. As a means of reducing the pathogen transfer to the internal egg contents, polysaccharide-based coatings containing antimicrobial phytochemicals could potentially serve as a biocontrol strategy for shelled egg products. The current study investigated the efficacy of four GRAS (Generally Recognized as Safe)-status plant-derived compounds, namely, caproic acid (CAO), caprylic acid (CAY), linalool (LIN) and cuminaldehyde (CUM), as pectin-based coating treatments, individually or in combination, for reducing Salmonella Heidelberg (SH) on shell eggs. A three-strain mixture of SH (~8.0 log CFU in 50 μL inoculum) was spot-inoculated on surface sterilized white-shelled eggs. Eggs were evenly coated with either pectin-based treatments of CAO (1%), CAY (1%), LIN (1%) and CUM (1%), individually, or a combination of 4 phytochemicals (COMB- each phytochemical at 0.5% v/v level of inclusion). The treated eggs were stored at 4°C and SH counts were enumerated on days 0, 1, 3, 5, 7, 14, and 21 of storage. The study was replicated thrice, 3 eggs/treatment/day time point, and the data were analyzed using two-way ANOVA with significance tested at p < 0.05. On day 0, pectin-coated control eggs had ~7.6 log CFU of SH/egg. At the end of refrigerated storage (day 21), pectin-based coating of CAO and CAY at 1% level reduced SH by 2.0–2.5 log CFU/egg (P < 0.05) when compared to controls. In addition, the CUM and LIN based coatings produced 3.0 log and 3.9 log reduction, respectively, in SH counts on eggs by day 21 of storage. Among the treatments with phytochemical combinations, COMB1 [pectin (2%) + Caprylic acid, caproic acid and cuminaldehyde (each at 0.5% level)] was found to be most effective, reducing SH counts to 2.5–3.3 log CFU/egg from day 0 through day 14, and by the end of storage period (day 21), a 3.5 log CFU reduction/egg (p < 0.05) compared to untreated controls. Morphological studies of treated eggs using atomic force microscopy (AFM) have shown that the roughness of eggs can be influenced by a combination of various compounds. Results indicate the potential efficacy of the aforesaid phytochemicals in reducing SH on shell eggs; however, further studies investigating their industrial feasibility and effects on sensory attributes of eggs are warranted.

Combined approach consisting of slightly acidic electrolyzed water and chitosan coating to improve the internal quality of eggs during storage

BACKGROUND

Slightly acidic electrolyzed water (SAEW) has been shown to offer a promising alternative for the inactivation of bacteria on egg surfaces, but the cuticle of the egg is damaged during this disinfection process. However, if SAEW disinfection is followed by chitosan (CS) coating treatment, this will construct a new membrane and prevent the loss of moisture and carbon dioxide through the damaged cuticle. Hence, the objective of this study was to investigate the efficacy of SAEW disinfection followed by CS coating treatment for improving the internal quality of eggs during 6 weeks of storage at 25 °C.

RESULTS

Scanning electron microscopy revealed that SAEW-treated eggs had deeper and wider cracks than control eggs stored between 0 and 21 days. Moreover, the depth and width of the cracks in the uncoated eggs increased as storage time increased. However, the CS coating method was successfully used on SAEW-disinfected eggs to construct a barrier against the negative effects of shell damage. After 6 weeks of storage at 25 °C, the yolk index, albumen pH, Haugh unit value and weight loss value of the SAEW + CS group were 0.31%, 9.01%, 63.72% and 5.35%, respectively.

CONCLUSIONS

A combination of SAEW and CS was more effective at maintaining internal egg quality than SAEW or CS treatments alone during storage. © 2020 Society of Chemical Industry.

A combined approach using slightly acidic electrolyzed water and UV exposure to improve egg internal quality during storage

This study investigated the combined efficacy of slightly acidic electrolyzed water (SAEW) and UV light (UV) in improving egg internal quality (weight loss, Haugh unit, yolk index, albumen pH) over a 6-wk storage time at 25°C. Eggs were preserved after immersion for 4 min in SAEW (30 mg/L), irradiation for 4 min under a UV lamp, or a combination of SAEW and UV treatment for 4 min. The combination of SAEW and UV inhibited the deterioration of yolk index over the storage period, as well as reducing the extent of decrease in Haugh unit and of weight loss during storage at 25°C, and it was more effective than SAEW or UV alone in maintaining egg internal quality (P < 0.05). The results highlight the promising use of a SAEW and UV combination treatment to improve egg internal quality during storage.

Effects of dietary glycerol monolaurate on productive performance, egg quality, serum biochemical indices, and intestinal morphology of laying hens

Glycerol monolaurate (GML) has been widely used as an effective antibacterial emulsifier in the food industry. A total of 360 44-week-old Hy-Line brown laying hens were randomly distributed into four groups each with six replicates of 15 birds, and fed with corn-soybean-meal-based diets supplemented with 0, 0.15, 0.30, and 0.45 g/kg GML, respectively. Our results showed that 0.15, 0.30, and 0.45 g/kg GML treatments significantly decreased feed conversion ratios (FCRs) by 2.65%, 7.08%, and 3.54%, respectively, and significantly increased the laying rates and average egg weights. For egg quality, GML drastically increased albumen height and Haugh units, and enhanced yolk color. Notably, GML increased the concentrations of polyunsaturated and monounsaturated fatty acids and reduced the concentration of total saturated fatty acids in the yolk. The albumen composition was also significantly modified, with an increase of 1.02% in total protein content, and increased contents of His (4.55%) and Glu (2.02%) under the 0.30 g/kg GML treatment. Additionally, GML treatments had positive effects on the lipid metabolism of laying hens, including lowering the serum triglyceride and total cholesterol levels and reducing fat deposition in abdominal adipose tissue. Intestinal morphology was also improved by GML treatment, with increased villus length and villus height to crypt depth ratio. Our data demonstrated that GML supplementation of laying hens could have beneficial effects on both their productivity and physiological properties, which indicates the potential application of GML as a functional feed additive and gives us a new insight into this traditional food additive.

Characterization, expression, and antimicrobial activity of histones from Japanese flounder Paralichthys olivaceus

Histone proteins are not only structurally important for chromosomal DNA packaging but also involved in the regulation of gene expression and the immune response of host against pathogens. Japanese flounder (Paralichthys olivaceus) as one of the most important marine flatfish, suffered from widespread outbreaks of diseases, and its immunological functioning remained to be elucidated. In the present study, we reported the expression patterns of four histones (H1, H2A, H3, and H3.3) and functional characterization of the histone H3.3 from flounder. Quantitative real time RT-PCR (RT-qPCR) analysis showed that expression of the four histones occurred in multiple tissues, but their levels of expression were relatively high in immune organs, and inducible in response to pathogens infection. Infection with extracellular and intracellular bacterial pathogens and viral pathogen regulated the expression of histones in a manner that depended on tissue type, pathogen, and infection stage. Specifically, H1 expression was highly induced by intracellular viral pathogens; H2AX and H3 expressions were highly induced by intracellular bacterial pathogen; dissimilarly, H3.3 expression was slightly induced by extracellular bacterial pathogen, but was inhibited by intracellular bacterial and viral pathogens. To further investigate H3.3 function, recombinant H3.3 (rH3.3) was obtained, and in vitro experiments showed rH3.3 possessed the capability of binding to both Gram-negative and Gram-positive bacteria and inhibiting the growth of some target bacteria. Consistently, In vivo results showed that overexpression of H3.3 promoted the host defense against invading pathogenic microorganism and regulated the expressions of several cytokines. These results suggested that flounder histones exhibit different expression patterns in response to the infection of different microbial pathogens, and H3.3 serves as an immune-related protein and plays an important role in antimicrobial immunity of Japanese flounder. Taken together, this study is the first report about the expression profile of different histones upon different kind of pathogens and anti-infectious immunity of H3.3 in teleost, which offered new insights into the immunological function of histones in teleost.

Effects of Chitosan Coating Structure and Changes during Storage on Their Egg Preservation Performance

To explore the influences of chitosan coating structure and structure changes during storage on egg preservation, eggs coated by chitosan solution for single time (CS1), two times (CS2), and three times (CS3) were prepared separately and stored with untreated eggs (CK1), eggs washed by water (CK2) and eggs treated by acetic acid solution (CK3) at 25 °C, 80% RH. The weight loss, Haugh unit, yolk index, albumen pH, eggshell morphologies and infrared (FTIR—Fourier Transform Infrared) spectra of all the samples were monitored. CS2 and CS3 presented the lowest weight loss, highest Haugh unit and yolk index, stabilized pH, and the highest thickness of chitosan coating layers (>2 μm) among all the groups, which extended egg shelf life for 20 days longer compared to CK1 and CK2. CS1 with very thin chitosan coating showed similar egg qualities with CK3, which are second only to CS2 and CS3. Furthermore, destructions were found on chitosan coatings during storage as revealed by the eggshell morphologies and FTIR spectra, which caused the quality deterioration of eggs. The results demonstrated that eggs with the thickest coating showed the best qualities during storage, while destructions on coating layers led to the quality drop of eggs.

Histones and chymotrypsin-like elastases play significant roles in the antimicrobial activity of tongue sole neutrophil extracellular traps

Neutrophil extracellular traps (NETs) are a form of extracellular antimicrobial structure of neutrophils observed in higher and lower vertebrates, the latter including the teleost fish tongue sole Cynoglossus semilaevis. However, the antimicrobial mechanism of fish NETs is unknown. In the present study, we examined the potential contribution of histones and elastases to the antibacterial effect of tongue sole NETs. For this purpose, two histones (CsH2B and CsH4) and two elastases (CsEla1 and CsEla2) of tongue sole were investigated. The histones and elastases possess the conserved domain structures characteristic of that of histones H2B/H4 and trypsin-like serine protease, respectively. Recombinant CsH2B, CsH4, CsEla1, and CsEla2 bound a wide range of Gram-negative and Gram-positive bacteria, and some of the bound bacteria were inhibited in growth by the bound histones/elastases. CsH2B, CsH4, CsEla1, and CsEla2 were all localized in NETs induced by various stimuli including bacterial pathogen. Treatment of NETs with antibodies targeting CsH2B, CsH4, CsEla1, and CsEla2 significantly reduced the antimicrobial effect of NETs. These results indicate that histones and chymotrypsin-like elastases are fundamental components of teleost NETs that play important roles in the antimicrobial activity of NETs.

Effect of chitosans and chitooligosaccharides on the processing and storage quality of foods of animal and aquatic origin

Purpose

– The aim of the paper is to shed light on the use of chitosans and chitooligosaccharides as biopreservatives in various foods animal. Foods of animal and aquatic origin (milk, meat, fish, eggs, sea foods, etc) become contaminated with a wide range of microorganisms (bacteria, molds and yeasts) during harvesting, transporting, processing, handling and storage operations. Due to the perishable nature of these foods, their preservation is of utmost importance. Though many synthetic chemicals are available, yet their use is quite restricted due to their hazardous effects on human health.

Design/methodology/approach

– Within the domain of food industry, traditionally chitosan is used for biopreservation of foods, which is well known for its nutritional and medicinal properties in human nutrition. However, chitooligosaccharides also possess a number of nutraceutical and health promoting properties in addition to their preservative effect and shelf-life extension of foods. In this study, the comparative effects of both chitosan and chitooligosaccharides on preservation of foods of animal and aquatic origin have been summarized.

Findings

– Though chitosan has been extensively studied in various foods, yet the use of chitooligosaccharides has been relatively less explored. Chitooligosaccharides are bioactive molecules generated from chitosan and have several advantages over the traditional use of chitosan both in food products and on human health. But unfortunately, little or no literature is available on the use of chitooligosaccharides for preservation of some of the foods of animal origin. Notable examples in this category include cheese, beef, pork, chicken, fish, sea foods, etc.

Originality/value

– This paper focuses on the effects of chitosans and chitooligosaccharides on the processing and storage quality of foods of animal and aquatic origin, which offers a promising future for the development of functional foods.

Antimicrobial property and microstructure of micro-emulsion edible composite films against Listeria

Edible antimicrobial composite films from micro-emulsions containing all natural compounds were developed and their antimicrobial properties and microstructures were investigated. Chitosan, allyl isothiocyanate (AIT), barley straw arabinoxylan (BSAX), and organic acids (acetic, lactic and levulinic acids) were used as film-forming agent, antimicrobial agent, emulsifier, and solvent, respectively. Micro-emulsions were obtained using high pressure homogenization (HPH) processing at 138MPa for 3cycles. The composite films made from the micro-emulsions significantly (p<0.05) inactivated Listeria innocua in tryptic soy broth (TSB) and on the surface of ready-to-eat (RTE) meat samples, achieving microbial reductions of over 4logCFU/ml in TSB after 2days at 22°C and on meat samples after 35days at 10°C. AIT was a major contributor to the antimicrobial property of the films and HPH processing further enhanced its antimicrobial efficacy, while the increase of chitosan from 1.5% to 3%, or addition of acetic acid to the formulations didn't result in additional antimicrobial effects. This study demonstrated an effective approach to developing new edible antimicrobial films and coatings used for food applications.

Effect of allyl isothiocyanate on developmental toxicity in exposed Xenopus laevis embryos

The pungent natural compound allyl isothiocyanate isolated from the seeds of Cruciferous (Brassica) plants such as mustard is reported to exhibit numerous beneficial health-promoting antimicrobial, antifungal, anticarcinogenic, cardioprotective, and neuroprotective properties. Because it is also reported to damage DNA and is toxic to aquatic organisms, the objective of the present study was to determine whether it possesses teratogenic properties. The frog embryo teratogenesis assay-Xenopus (FETAX) was used to determine the following measures of developmental toxicity of the allyl isothiocyanate: (a) 96-h LC50, defined as the median concentration causing 50% embryo lethality; (b) 96-h EC50, defined as the median concentration causing 50% malformations of the surviving embryos; and (c) teratogenic malformation index (TI), equal to 96-h LC50/96-h EC50. The quantitative results and the photographs of embryos before and after exposure suggest that allyl isothiocyanate seems to exhibit moderate teratogenic properties. The results also indicate differences in the toxicity of allyl isothiocyanate toward exposed embryos observed in the present study compared to reported adverse effects of allyl isothiocyanate in fish, rodents, and humans. The significance of the results for food safety and possible approaches to protect against adverse effects of allyl isothiocyanate are discussed.