The current situation for the water sources in the Maltese Islands

This commentary addresses issues related to the scarcity of water in the Maltese Islands and its main causes. Some basic metrics related to the abstraction of freshwater, contamination of groundwater by nitrate and the limitations and challenges of the water sources in the Maltese Islands are highlighted. Hereafter, the relation between water scarcity, rainfall and population density, as well as the resultant effects on the sustainability of the freshwater sources of the Maltese Islands are presented. The current focus is on the production of good quality water based on a number of Reverse Osmosis (RO) plants that are found around the Maltese Islands. The significant energy requirements of this technology are compared with those for groundwater and wastewater treatment production. Current practices in the Maltese Islands regarding the treatment and use of sewage effluent by Sewage Treatment Plants (STPs) are described. The use of treated sewage effluent as an alternative source of water to RO water and of groundwater for second class uses is discussed. This paper concludes that the technology needed to employ treated effluents for unrestricted agricultural use and also for aquifer recharge is now in existence.peer-reviewe

Assessing the Microbial Oxidative Stress of Ozone: Significant Role of the Oxidative Stress Proteins in the Survival of E. coli in Ozone Treatment

Aims: To investigate the effect of the oxidative stress of ozone on microbial inactivation, cell membrane integrity, membrane permeability and morphology changes of Escherichia coli during ozone treatment. Methods and Results: E. coli BW 25113 and its isogenic mutants in soxR, soxS, oxyR, rpoS, dnaK genes were treated with ozone at a concentration of 6 µg mL-1 for a period up to 4 min. A significant effect of ozone exposure on microbial inactivation was observed. After ozonation, minor effects on the cell membrane integrity and permeability were observed. Scanning Electron Microscopy (SEM) analysis showed slightly altered cell surface structure. Conclusions: The results of this study suggest that cell lysis was not the major mechanism of microbial inactivation. The deletion of oxidative stress-related genes resulted in increased susceptibility of E. coli cells to ozone treatment, implying that they play an important role for protection against the radicals produced by ozone. However, DnaK which has previously been shown to protect against oxidative stress did not protect against ozone treatment in this study. Furthermore, RpoS was important for survival against ozone through as of yet unidentified mechanism. Significance and impact of the study: This study provides important information about the role of oxidative stress related proteins in E. coli survival during ozonatio

Assessing the Mechanism of Microbial Inactivation during Ozone Pocessing

Ozone has numerous applications in food industry because of its advantages over traditional preservation techniques. Damage to cell membranes and cytoplasmic contents was proposed as involved in ozone inactivation but there is no available information concerning oxidative stress effect of ozone on regulated knockout genes and the protection or sensitivity of microbial mutants (lacking these genes) against ozone or ozone generated radicals. The aim of this work was to investigate the mechanism of action of ozone on microbial populations during the treatment of liquid food systems. E. coli BW25113 and its isogenic mutants in soxR, soxS, oxyR, rpoS, dnaK genes were treated with ozone at a previously optimized concentration of 6µg/mL for a period up to 4 min in a 100 mL bubble column. Ozone gas was generated using a corona discharge ozone generator. Oxygen was supplied via air cylinder and the flow rate (0.06 L/min) was controlled using a flow regulator. A significant effect of ozone exposure on microbial inactivation was observed while the cell membrane integrity and permeability were affected by ozonation. Scanning Electron Microscopy (SEM) analysis showed slightly altered cell surface structure. The results of this study suggest that cell lysis was not the primary mechanism of microbial inactivation. The absence of oxidative stress-related genes resulted in increased susceptibility of E. coli cells to ozone treatment suggesting that they play an important role for protection against the radicals produced by ozone. However, DnaK which has previously been shown to protect against oxidative stress did not protect against ozone treatment. Furthermore, RpoS was important for survival against ozone through an unidentified mechanism. This preliminary study provides important information about the mechanism through which ozonation acts against microorganisms for the production of safe liquid food products

An Alternative Approach to Non-Log-Linear Thermal Microbial Inactivation: Modelling the Number of Log Cycles Reduction with Respect to Temperature

A mathematical approach incorporating the shoulder effect during the quantification of microbial heat inactivation is being developed based on »the number of log cycles of reduction « concept. Hereto, the heat resistance of Escherichia coli K12 in BHI broth has been quantitatively determined in a generic and accurate way by defining the time t for x log reductions in the microbial population, i.e. txD, as a function of the treatment temperature T. Survival data of the examined microorganism are collected in a range of temperatures between 52–60.6 °C. Shoulder length Sl and specific inactivation rate kmax are derived from a mathematical expression that describes a non-log-linear behaviour. The temperature dependencies of Sl and kmax are used for structuring the txD(T) function. Estimation of the txD(T) parameters through a global identification procedure permits reliable predictions of the time to achieve a pre-decided microbial reduction. One of the parameters of the txD(T) function is proposed as »the reference minimum temperature for inactivation«. For the case study considered, a value of 51.80 °C (with a standard error, SE, of 3.47) was identified. Finally, the time to achieve commercial sterilization and pasteurization for the product at hand, i.e. BHI broth, was found to be 11.70 s (SE=5.22), and 5.10 min (SE=1.22), respectively. Accounting for the uncertainty (based on the 90 % confidence intervals, CI) a fail-safe treatment of these two processes takes 20.36 s and 7.12 min, respectively

Characterization of indigenous lactic acid bacteria in cow milk of the Maltese Islands : a geographical and seasonal assessment

A geographical and seasonal assessment of indigenous lactic acid bacteria (LAB) in Maltese cow milk was conducted in this study. To investigate this, milk was collected from different regions of Malta during winter and summer seasons. Total viable counts (TVC) and LAB population were enumerated. Afterwards, LAB were isolated and identified by molecular methods. According to the results, similar TVC were enumerated on winter and summer samples, while highest LAB population was detected on summer samples. LAB isolates were grouped in seven different clusters which were assigned to Lactobacillus casei, Pediococcus pentosaceus, Lactobacillus plantarum, Weissella paramesenteroides, Lactobacillus rhamnosus, Lactococcus lactis, and Lactococcus garvieae. In addition, Enterococcus and Streptococcus species were also isolated. Season seemed to affect the genus / species of LAB since Lactobacillus were mainly isolated from winter samples, while Lactococcus and Enterococcus species were the main genera identified in summer samples. Regarding the geographical distribution, the majority of the Lactobacillus spp. were isolated from the South-eastern region in both seasons. In conclusion, through this study the diversity of indigenous LAB in the Maltese cow milk was monitored for the first time and highlighted that the microbial communities are affected by seasonality and geographical distribution of the farms.peer-reviewe

Bioactive natural products: facts, applications, and challenges

License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Today, there are a strong debate and interest regarding the safety aspects of chemical preservatives addedwidely inmany food products to prevent mainly growth of spoilage and pathogenic microbes. Synthetic compounds are considered responsible for carcinogenic and teratogenic attributes and residual toxicity. To avoid the aforementioned problems, consumers and authorities have increased pressure on food manufacturers to substitute the harmful artificial additives with alternative, more effective, nontoxic, and natural sub-stances. In this context, the use of natural compounds with antimicrobial action presents an intriguing case. Natural antioxidants also demonstrate a wide range of biological and pharmacological activities and are considered to have bene

Determination of the efficacy of ultrasound combined with essential oils on the decontamination of Salmonella inoculated lettuce leaves

Salmonella is one of main pathogenic bacteria present in fresh produce. Ultrasound has been reported to be effective at inactivating food-borne pathogens. Moreover, ultrasound can be combined with essential oils to enhance its efficacy. This study evaluates the reduction and inactivation of Salmonella enterica Abony inoculated on lettuce leaves by the application of continuous and pulsed ultrasound as well as ultrasound combined with the essential oil of oregano and thyme. The physicochemical properties of these essential oil nanoemulsions are characterised while the structural damage of treated leaves is determined by the electrolyte leakage. Ultrasound combined with essential oils enhanced the microbial reduction on lettuce leaves and inactivation on the treated water, resulting on significant differences at concentrations higher than 0.018% (v/v) compared to control. Particle size, zeta potential and pH varied between 35 and 133 nm, −26 to −36 mV and 5.67 to 5.38, respectively. Electrolyte leakage was similar for both the control and the treated samples, increasing when essential oils were applied.peer-reviewe

Application of Natural Antimicrobials for Food Preservation

In this review, antimicrobials from a range of plant, animal, and microbial sources are reviewed 10 along with their potential applications in food systems. Chemical and biochemical antimicrobial 11 compounds derived from these natural sources and their activity against a range of pathogenic and 12 spoilage microorganisms pertinent to food, together with their effects on food organoleptic proper- 13 ties, are outlined. Factors influencing the antimicrobial activity of such agents are discussed 14 including extraction methods, molecular weight, and agent origin. These issues are considered in 15 conjunction with the latest developments in the quantification of the minimum inhibitory (and 16 noninhibitory) concentration of antimicrobials and/or their components. Natural antimicrobials can 17 be used alone or in combination with other novel preservation technologies to facilitate the 18 replacement of traditional approaches. Research priorities and future trends focusing on the impact 19 of product formulation, intrinsic product parameters, and extrinsic storage parameters on the design 20 of efficient food preservation systems are also presented