Natural Antimicrobials Suitable for Combating Desiccation-Resistant Salmonella enterica in Milk Powder

Some Salmonella enterica strains survive well in low-water activity (low-aw) foods and cause frequent salmonellosis outbreaks in these products. Methods are needed to overcome such desiccation-resistant Salmonella and to improve the safety of low-aw foods. Building on a recent finding, we hypothesized that natural antimicrobial food additives, which are active against cytoplasmic membrane, could overcome this desiccation resistance phenomenon, and thus, sensitize the pathogen to drying and mild processing. Food additives were screened for the ability to cause leakage of intracellular potassium ions; retention of these ions is vital for protecting Salmonella against desiccation. Two antimicrobial food additives, carvacrol and thymol, caused considerable potassium leakage from the desiccation-resistant S. enterica serovars, Tennessee and Livingstone. Thus, carvacrol and thymol were investigated for their ability to sensitize the desiccation-adapted S. enterica to heat treatment. The combined use of food additives, at their minimum inhibitory concentrations, with heat treatment at 55 °C for 15 min caused 3.1 ± 0.21 to more than 5.5 log colony forming unit (CFU)/mL reduction in desiccation-adapted S. enterica, compared to 2.4 ± 0.53–3.2 ± 0.11 log CFU/mL reduction by sole heat treatment. Carvacrol was the additive that caused the greatest potassium leakage and sensitization of Salmonella to heat; hence, the application of this compound was investigated in a food model against Salmonella Typhimurium ASD200. Addition of carvacrol at 200 or 500 ppm into liquid milk followed by spray-drying reduced the strain’s population by 0.9 ± 0.02 and 1.3 ± 0.1 log CFU/g, respectively, compared to 0.6 ± 0.02 log CFU/g reduction for non-treated spray-dried milk. Additionally, freeze-drying of milk treated with high levels of carvacrol (5000 ppm) reduced the population of Salmonella Typhimurium ASD200 by more than 4.5 log CFU/g, compared to 1.1 ± 0.4 log CFU/g reduction for the freeze-dried untreated milk. These findings suggest that carvacrol can combat desiccation-resistant S. enterica, and thus, potentially improve the safety of low-aw foods.

Acetone washing for the removal of lichen substances affects membrane permeability

Removing lichen substances from dry lichen thalli using pure acetone is the least detrimental method. Measurements of properties strictly related to the photobiont, such as chlorophyllafluorescence (ChlaF), are frequently used to verify acetone toxicity but they cannot reveal possible damage accumulated at the whole thallus level. Here, measurements of ChlaF have been integrated with others concerning the status of cell membranes and photobiont population (potassium leakage, malondialdehyde and photosynthetic pigment content). Dry thalli ofFlavoparmelia caperata,Parmotrema perlatumandXanthoria parietinawere subjected to sequential acetone washings according to standard protocols. Membrane permeability was assessed before and after the washing treatment, and after a recovery period of 48 hours. Measurements of ChlaF were taken in a parallel experiment. Acetone washings increased potassium leakage in all the species from 3·9 to 6·6 times greater than the control level. After recovery, onlyP. perlatumreturned to the control level. ChlaF was affected only inF. caperata, with a 20% decrease inFv/Fmwhich had not fully recovered after 48 hours. There was neither an increase in lipid peroxidation of membranes nor a change in the photosynthetic pigment content. The sensitivity ofF. caperatato this method and the impact of the results on its future application are discussed.

Electrical conductivity for seed vigor test in sorghum (Sorghum bicolor)

Fatonah K, Suliansyah I, Rozen N. 2017. Electrical conductivity for seed vigor test in sorghum (Sorghum bicolor). Cell Biol Dev 1: 6-12. The objectives of this study were to obtain electrical conductivity test method for seed vigor test in sorghum, to recognize relationship between electrical conductivity test and potassium leakage, and to recognize relationship between electrical conductivity test and other variable on seed vigor. This study have two step experiments. The objective of Experiment I was to determine accurate combinations of water volume and amount seed of the electrical conductivity test for seed vigor test in sorghum. Completely Randomized Design of 15 seed lots with 3 replications were used to determine electrical conductivity method with different vigor. Experiment II were to test electrical conductivity method of 21 seed lots of sorghum without accelerated aging test and 21 seed lots of sorghum were given accelerated aging test. Completely Randomized Design of 21 seed lots with 3 replications were used in Experiment II. The variable were observed : standard germination, field emergence, speed of germination, first count, conductivity, potassium leakage and eight combination conductivity method of water volume (50, 100, 150 and 200 ml) and amount of seed sorghum (50 and 75 seed count). The result of this experiments showed that electrical conductivity test method with 150 ml water volume and 75 seed count was accurate and suitable for sorghum seed vigor test; electrical conductivity test showed positive correlation with potassium leakage;and electrical conductivity test can be used for seed vigor test in sorghum and provided the potential of physiological seed were shown through : standard germination test, field emergence test, first count test and speed of germination with negative correlation.

Fine-tuning of the hydrophobicity of caffeic acid: studies on the antimicrobial activity against Staphylococcus aureus and Escherichia coli

Caffeic acid derivatives are proposed to act as cell permeabilizers, inducing membrane alterations, causing rupture with potassium leakage, particularly on the Gram positive bacterium, and consequent cell death.

Physiological potential of cauliflower seeds

The assessment of seed physiological performance is essential to provide consistent information to compose quality control programs conducted by seed companies and allow prompt decisions to reduce post-harvest and commercialization problems. This research was carried to evaluate the efficiency of different procedures to determine cauliflower seed vigor. Six lots of the cultivar Sharon were initially characterized by germination and seedling emergence, and subsequently subjected to traditional and saturated salt accelerated aging, controlled deterioration, electrical conductivity, and potassium leachate tests, in two evaluation times. The traditional accelerated aging (41ºC/48 h), the saturated salt procedure (45ºC/72 h), the controlled deterioration (moisture content adjusted to 20% or 22% and aging at 45ºC/24 h), the electrical conductivity (50 seeds/75 mL water and evaluation after 4 h) and the potassium leakage (25 seeds/50 mL of water and evaluation after 30 min) laboratory tests are sensitive to detect differences in the physiological potential of cauliflower seeds. However, those results did not relate to the percentage seedling emergence in greenhouse controlled conditions, as a consequence of the favorable conditions for emergence. However, the differences identified in the tests may be related to the ability of seed lots to perform in less favorable environments.

Biological Activity of New N-Oxides of Tertiary Amines

Potential biological properties of newly synthesized single and double alkyl chain N-oxides of tertiary amines (NTA) were studied. Individual compounds in each of the series had alkyl chains of different length. Various experiments were performed to determine a mechanism of the interaction between NTA and model and biological membranes. These were measurements of hemolytic efficiencies of NTA (pig erythrocytes), their influence on the transition temperatures (DPPC liposomes), on potassium leakage from cucumber, its growth and chlorophyll content (Cucumis sativus cv. Krak F1), and on the resting membrane potential in alga cells (Nitellopsis obtusa). Also, prevention of erythrocyte membrane lipid oxidation induced by UV irradiation was studied. Potential antioxidative properties of NTA were additionally tested in radical chromogen (ABTS●+) experiments in which antioxidative efficiencies of NTA were compared to that of the standard antioxidant Trolox. It was found that NTA readily interacted with erythrocyte membranes. Their hemolyzing efficiency increased with the alkyl chain length. Slightly more intensive interaction was found for double alkyl chain compounds. Similar results were obtained in DSC experiments, where incorporation of NTA into liposomal membranes shifted the main transition temperatures and caused a broadening of the main transition peaks depending on the alkyl chain length. Double alkyl chain compounds were also found more efficiently influencing the growth of cucumber. Influence of NTA on the resting membrane potential of algae cells was not quite following the alkyl chain length rule found in erythrocyte and liposome experiments. Also potassium leakage and chlorophyll content determined in physiological experiments were not following the increase of lipophilicity of compounds. Most efficiently influencing those parameters were NTA having shorter alkyl chains, and efficiencies of single alkyl chain compounds were evidently stronger. Both methods used to test the antioxidative properties of NTA showed that they depended on the alkyl chain lengths of compounds within each series, but double alkyl chain ones exhibited markedly greater efficiency.