Enhancing the quality and safety of Nocellara del Belice green table olives produced using the Castelvetrano method

The Castelvetrano method is the most widely used among the various table olive processing styles in Sicily. After debittering, the product is stored at low temperatures to prevent the growth of undesirable microorganisms. In an effort to enhance the production process, yeast isolates underwent genotypic characterization and technological screening. The screening process identified two yeast strains Candida norvegica OC10 and Candida boidinii LC1, which can grow at low temperatures and tolerate high pH values (up to 10) and salinity [10% (w/v)]. During the monitoring period, the inoculated trials showed limited presence of spoilage/pathogenic microorganisms. Additionally, the yeasts limited oxidative phenomena and softening of the drupes. The organic compounds detected were higher in the inoculated trials than in the control, and cold storage induced aromatic decay, which was less pronounced in the trial inoculated with C. norvegica. Sensory analysis revealed that the inoculated trials scored higher in sweetness, hardness and crispness.

A selection process based on the robustness of anti-Listeria monocytogenes activity reveals two strains of Carnobacterium maltaromaticum with biopreservation properties in cheese

Biopreservation is an approach consisting of using microorganisms as protective cultures and/or their metabolites to optimize the microbiological quality and shelf life of food by ensuring safety or reducing food waste. Biopreservation strain selection pipelines mainly focus on inhibition strength to identify strains of interest. However, in addition to inhibition strength, inhibition activity must be able to be expressed despite significant variations in food matrix properties. In this study, the anti-Listeria monocytogenes EGDelux properties of a collection of 77 Carnobacterium maltaromaticum strains were investigated by high throughput competition assays under varying conditions of co-culture inoculation level, time interval between inoculation with C. maltaromaticum and L. monocytogenes, pH, and NaCl, resulting in 1309 different combinations of C. maltaromaticum strains and culture conditions. This screening led to the selection of two candidate strains with potent and robust anti-L. monocytogenes activities. Deferred growth inhibition assays followed by halo measurements, and liquid co-culture followed by colony counting, revealed that these two strains exhibit a wide anti-Listeria spectrum. Challenge tests in Camembert and Saint-Nectaire cheese revealed both strains were able to inhibit a cocktail of five strains of L. monocytogenes with high potency and high reproducibility. These results highlight the importance of including the robustness criterion in addition to potency when designing a strain selection process for biopreservation applications.

Identification of antagonistic yeasts as potential biocontrol agents: Diverse criteria and strategies

Plant pathogenic and food spoilage microorganisms cause serious losses in crop production and severe damage during food manufacturing, transportation and storage. Synthetic antimicrobial agents are commonly used to control their propagation and harmful activities. However, the recent trend is shifting from chemicals towards safer and more eco-friendly alternatives. The use of antagonistic microorganisms as biological antimicrobial agents is becoming popular throughout the world to replace chemical agents. High numbers of microorganisms have turned out to exert adverse/inhibitory effects on other microorganisms including pathogens and spoiling strains. However, most of them are only active under laboratory conditions and their activity is sensitive to environmental changes. Only a small number of them can be used to manufacture biological protective products on an industrial scale. Therefore, there is a great need to identify additional antagonists. Yeasts have come to the forefront of attention because antimicrobial antagonism is fairly widespread among them. In the recent years, numerous excellent review articles covered various aspects of the phenomenon of antimicrobial antagonism of yeasts. However, none of them dealt with how antagonistic yeasts can be sought and identified, despite the high number and diverse efficiency of screening and identification procedures. As researchers working in different laboratories use different criteria and different experimental set-ups, a yeast strain found antagonistic in one laboratory may prove to be non-antagonistic in another laboratory. This review aims to provide a comprehensive and partially critical overview of the wide diversity of identification criteria and procedures to help researchers choose appropriate screening and identification strategies.

Bioprotection by non-Saccharomyces yeasts in oenology: Evaluation of O2 consumption and impact on acetic acid bacteria

Bioprotection by yeast addition is increasingly used in oenology as an alternative to sulfur dioxide (SO2). Recent studies have also shown that it is likely to consume dissolved O2. This ability could limit O2 for other microorganisms and the early oxidation of the grape must. However, the ability of yeasts to consume O2 in a context of bioprotection was poorly studied so far considering the high genetic diversity of non-Saccharomyces. The first aim of the present study was to perform an O2 consumption rate (OCR) screening of strains from a large multi species collection found in oenology. The results demonstrate significant inter and intra species diversity with regard to O2 consumption. In the must M. pulcherrima consumes O2 faster than Saccharomyces cerevisiae and then other studied non-Saccharomyces species. The O2 consumption was also evaluate in the context of a yeast mix used as industrial bioprotection (Metschnikowia pulcherrima and Torulaspora delbrueckii) in red must. These non-Saccharomyces yeasts were then showed to limit the growth of acetic acid bacteria, with a bioprotective effect comparable to that of the addition of sulfur dioxide. Laboratory experiment confirmed the negative impact of the non-Saccharomyces yeasts on Gluconobacter oxydans that may be related to O2 consumption. This study sheds new lights on the use of bioprotection as an alternative to SO2 and suggest the possibility to use O2 consumption measurements as a new criteria for non-Saccharomyces strain selection in a context of bioprotection application for the wine industry.

Damaging and protective interactions of lichens and biofilms on ceramic dolia and sculptures of the International Museum of Ceramics, Faenza, Italy

Although ceramic objects are an important part of the worldwide cultural heritage, few investigations on the effects of lithobiontic growth on their outdoor conservation are available in the literature. Many aspects of the interaction between lithobionts and stones are still unknown or strongly debated, as in the case of equilibria between biodeterioration and bioprotection. This paper describes research on the colonization by lithobionts on outdoor ceramic Roman dolia and contemporary sculptures of the International Museum of Ceramics, Faenza (Italy). Accordingly, the study i) characterized the mineralogical composition and petrographic structure of the artworks, ii) performed porosimetric measurements, iii) identified lichen and microbial diversity, iv) elucidated the interaction of the lithobionts with the substrates. Moreover, v) the measurements of variability in stone surface hardness and in water absorption of colonized and uncolonized areas were collected to assess damaging and/or protective effects by the lithobionts. The investigation showed how the biological colonization depends on physical properties of the substrates as well on climatic conditions of environments in which the ceramic artworks are located. The results indicated that lichens Protoparmeliopsis muralis and Lecanora campestris may have a bioprotective effect on ceramics with high total porosity and pores with very small diameters, as they poorly penetrate the substrate, do not negatively affect surface hardness and are able to reduce the amount of absorbed water limiting the water ingress. By contrast, Verrucaria nigrescens, here widely found in association with rock-dwelling fungi, deeply penetrate terracotta causing substrate disaggregation, with negative consequences on surface hardness and water absorption. Accordingly, a careful evaluation of the negative and positive effects of lichens must be carried out before deciding their removal. Regarding biofilms, their barrier efficacy is related to their thickness and composition. Even if thin, they can impact negatively on substrates enhancing the water absorption in comparison to uncolonized parts.

Selection of food cultures with protective properties for cooked ham

Sliced cooked ham stored in modified atmosphere packaging (MAP) can be spoiled by lactic acid bacteria (LAB) which are dominating under psychrotrophic conditions. Depending on the strains, the colonization can result in a premature spoilage characterized by off-flavors, gas and slime production, discoloration, and acidification. The purpose of this study was the isolation, identification and characterization of potential food culture with protective properties, able to prevent or delay spoilage in cooked-ham. The first step was to identify by means of microbiological analysis, the microbial consortia both in unspoiled and in spoiled lots of sliced cooked ham by the use of media for the detection lactic acid bacteria and total viable count. Counts ranged from values lower than 1 Log CFU/g to 9 Log CFU/g in spoiled and unflawed samples. The interaction between consortia was then studied in order to screen for strains able to inhibit spoilage consortia. Strains showing antimicrobial activity were identified and characterized by molecular methods and tested for their physiological features. Among a total of 140 strains isolated, nine were selected for their ability to inhibit a large number of spoilage consortia, to grow and ferment at 4 °C and to produce bacteriocins. The effectiveness of the fermentation made by food culture was evaluated, through challenge tests in situ, analysing the microbial profiles of artificially inoculated cooked-ham slices during storage by high throughput 16 S rRNA gene sequencing. The native population in situ resulted competitive against the inoculated strains and only one strain was able to significantly reduce the native populations reaching about 46.7% of the relative abundance. The results obtained in this study provide information about the selection of autochthonous LAB on the base of their action against spoilage consortia, in order to select protective potential cultures able to improve the microbial quality of sliced cooked ham.

Thermoresponsivity of poly(N-isopropylacrylamide) microgels in water-trehalose solution and its relation to protein behavior

HYPOTHESES

Additives are commonly used to tune macromolecular conformational transitions. Among additives, trehalose is an excellent bioprotectant and among responsive polymers, PNIPAM is the most studied material. Nevertheless, their interaction mechanism so far has only been hinted without direct investigation, and, crucially, never elucidated in comparison to proteins. Detailed insights would help understand to what extent PNIPAM microgels can effectively be used as synthetic biomimetic materials, to reproduce and study, at the colloidal scale, isolated protein behavior and its sensitivity to interactions with specific cosolvents or cosolutes.

EXPERIMENTS

The effect of trehalose on the swelling behavior of PNIPAM microgels was monitored by dynamic light scattering; Raman spectroscopy and molecular dynamics simulations were used to explore changes of solvation and dynamics across the swelling-deswelling transition at the molecular scale.

FINDINGS

Strongly hydrated trehalose molecules develop water-mediated interactions with PNIPAM microgels, thereby preserving polymer hydration below and above the transition while drastically inhibiting local motions of the polymer and of its hydration shell. Our study, for the first time, demonstrates that slowdown of dynamics and preferential exclusion are the principal mechanisms governing trehalose effect on PNIPAM microgels, at odds with preferential adsorption of alcohols, but in full analogy with the behavior observed in trehalose-protein systems.

Increased soybean tolerance to water deficiency through biostimulant based on fulvic acids and Ascophyllum nodosum (L.) seaweed extract

To meet the growing demand for soybean it is necessary to increase crop yield, even in low water availability conditions. To circumvent the negative effects of water deficit, application of biostimulants with anti-stress effect has been adopted, including products based on fulvic acids and Ascophyllum nodosum (L.) seaweed extracts. In this study, we determined which formulation and dosage of a biostimulant is more efficient in promoting the recovery of soybean plants after stress due to water deficit. The experiment was conducted in a greenhouse, in a double-factorial randomized block design with two additional factors, four repetitions and eleven treatments consisting of three biostimulant formulations (F1, F2 and F3), and three dosages (0.25; 0.50 and 1.0 kg ha-1); a control with water deficit and a control without water deficit. Soybean plants were kept at 50% of the pot's water capacity for three days, then rehydrated and submitted to the application of treatments with biostimulant. After two days of recovery, growth, physiological, biochemical and yield parameters were evaluated. All plants that received the application of the biostimulant produced more than the water-stressed control plants. The biostimulant provided higher photosynthetic rates, more efficient mechanisms for dissipating excess energy and higher activities of antioxidant enzymes. Plants treated with biostimulant were more efficient in the recovery of the metabolic activities after rewatering, resulting in increased soybean tolerance to water deficit and reduced yield losses. The best result obtained was through the application of formulation 2 of the biostimulant at a dosage of 0.25 kg ha-1.

How we can improve the antimicrobial performances of lactic acid bacteria? A new strategy to control Listeria monocytogenes in Gorgonzola cheese

This study was aimed to evaluate the effectiveness of two lactic acid bacteria (LAB) cultures (Lactococcus lactis FT27 and Carnobacteroim divergens SCA), lactic acid/sodium lactate (LASL - l-lactic acid 61% (w/w) and L-sodium lactate 21% (w/w)) and their combination against four Listeria monocytogenes biotypes isolated from Gorgonzola cheese. In vitro antilisterial activity showed that the sensitivity to antimicrobials was strain-dependent. Antimicrobial challenge testing was performed on Gorgonzola rinds simulating contamination occurring at the beginning (6 days) and at the end (55 days) of the ripening period, to assess the antilisterial activity of LAB strains and LASL during the subsequent 60 days at 4 °C. LASL showed a higher antilisterial activity than LAB, maintaining the pathogen content below the EC limit (<2.0 log₁₀ CFU/g) for 60 days. A strong listericidal effect was observed combining LAB with LASL (2,8 μL/cm²) Lc. lactis in combination with LASL completely inhibited the two L. monocytogenes strains in the first 50 days, while LASL with C. divergens was more effective in the second part of ripening when the pH raised. Data obtained encourage the use of LASL along with antimicrobial LAB rotation schemes during cheese ripening for the prevention and/or control of the L. monocytogenes on cheese surface.

Performance of two differently designed permeable reactive barriers with sulfate and zinc solutions

For the first time, this laboratory-scale study evaluates the feasibility of incorporating diffusive exchange in permeable reactive barriers. In order to do this, the performance of two permeable reactive barriers (PRB) with different internal substrate arrangements were compared during the administration of a sulfate solution without metals (for 163 days) and with metals (for 60 days), simulating groundwater contaminated with acid mine drainage (AMD). In order to simulate a traditional PRB, a homogeneous distribution was implemented in the first reactor and the other PRB reactor utilized diffusion-active technology (DAPRB). In the DAPRB, the distribution of the reactive material was interspersed with the conductive material. The measurements in the internal ports showed that transverse gradients of sulfide formed in the DAPRB, causing the diffusion of sulfide from the substrate toward the layer interface, which is where the sulfide reacts by forming complexes with the metal. The DAPRB prevents the microorganisms from direct contact with AMD. This protection caused greater activity (sulfide production).

Comparison of the effect of a hyaluronate-trehalose solution to hyaluronate alone on Ocular Surface Disease Index in patients with moderate to severe dry eye disease

OBJECTIVE

To describe a post hoc analysis comparing the effect of a hyaluronic acid (HA)-trehalose solution to an established eyedrop solution containing HA alone using Ocular Surface Disease Index (OSDI) score <19 as a threshold for moderate to severe dry eye disease (DED).

METHODS

A phase III, randomized, controlled, single-blind, multicenter study was conducted in France and Tunisia to evaluate the efficacy and safety of HA-trehalose (N = 52) and HA (N = 53) administered for 84 days. Eligible patients had moderate to severe DED with OSDI ≥18. Here the results of a post hoc analysis of the percentage of patients with OSDI <19 on Day 35 and Day 84 are reported.

RESULTS

Significantly more patients had OSDI <19 at Day 84 in the HA-trehalose group than in the HA group (78.8% versus 58.5%; p = .025). At Day 35, more patients had OSDI <19 in the HA-trehalose group than in the HA group, but this difference was not statistically significant. Furthermore, approximately twice as many patients in the HA group (41.5%) still had OSDI 19-100 at Day 84 compared to the HA-trehalose group (21.2%).

CONCLUSIONS

This data supports the addition of trehalose to HA-containing eyedrop solutions to provide better symptomatic relief from moderate to severe DED, based on an OSDI score of <19 after 84 days of treatment.

Bioerosive and bioprotective role of barnacles on rocky shores

Bioerosion and bioprotection (bio-remodeling) is the action exerted by biota colonizing rocky shores. It represents an important component among processes responsible for shaping coastal landforms, and a clear evidence of interaction between the biosphere and the solid earth. Barnacles extensively colonize the midlittoral belt of rocky shores in the Mediterranean Basin. Previous research, mostly based on laboratory evidence, suggests that barnacles are bioprotectors, in that they protect the rock surface from different types of physical and chemical weathering. In this paper, we present the results of a field experiment carried out at different spatial scales at two study areas along the moderately energetic and microtidal coast of NW Italy. Barnacles were removed from the sandstone bedrock in replicated plots (manipulated plots) arranged according to a hierarchical spatial design. After four months rock hardness was tested on each plot with both Schmidt hammer and Equotip Piccolo devices, as well as on a corresponding number of control plots. Data were processed by means of a multifactorial analysis of variance (ANOVA). In control plots, rock hardness tested with Schmidt hammer exceeded that measured in previously manipulated plots. Testing with Equotip yielded the opposite results. This experimental evidence confirmed that barnacles play a bio-protective role in the midlittoral at sub-surficial level, while adding the key aspect that this effect is generalizable to spatial scales ranging from a few centimeters up to tens of kilometers. In addition, our results showed, for the first time, that at surface level they can simultaneously act as bioeroders, likely causing corrosion of the rock surface by fostering dissolution of the sandstone carbonate matrix.

The most important inferences from the Ekaterinburg nanotoxicology team's animal experiments assessing adverse health effects of metallic and metal oxide nanoparticles

During 2009-2017 we have studied nanoparticles of elemental silver or gold and of iron, copper, nickel, manganese, lead, zinc, aluminium and titanium oxides (Me-NPs) using, in most cases, a single low-dose intratracheal instillation 24 h before the bronchoalveolar lavage to obtain a fluid for cytological and biochemical assessment and, in all cases, repeated intraperitoneal injections in non-lethal doses to induce subchronic intoxications assessed by a lot of toxicodynamic and toxicokinetic features. We have also studied the same effects for a number of relevant combinations of these Me-NPs and have revealed some important patterns of their combined toxicity. Besides, we have carried out long-term inhalation experiments with Fe2O3, NiO and amorphous SiO2 nano-aerosols. We have demonstrated that Me-NPs are much more noxious as compared with their fine micrometric counterparts although the physiological mechanisms of their elimination from the lungs proved to be highly active. Even if water-insoluble, Me-NPs are significantly solubilized in some biological milieus in vitro and in vivo, which may explain some important peculiarities of their toxicity. At the same time, the in situ cytotoxicity, organ-systemic toxicity and in vivo genotoxicity of Me-NPs strongly depends on specific mechanisms characteristic of a particular metal. For some of the Me-NPs studied, we have proposed standards of presumably safe concentrations in workplace air. Along with this, we have proved that the adverse effects of Me-NPs could be significantly alleviated by background or preliminary administration of adequately composed combinations of some bioprotectors.

Optimization of reuterin production in cheese by Lactobacillus reuteri

Cheeses manufactured from pasteurized milk supplemented with glycerol and reuterin-producing Lactobacillus reuteri INIA P572 as adjunct to the commercial starter culture were analysed in order to optimize a biopreservation strategy. The highest reuterin concentration determined by a colorimetric assay was detected on day 1 in cheeses with 100-500 mM glycerol. The presence of reuterin was confirmed by a direct detection technique as HPLC. Cheeses made with L. reuteri and 200 or 500 mM glycerol showed a red tendency in color in comparison with control. The results with purified reuterin suggested that the development of slightly rosy colour in cheese was related to some compound produced/overproduced when higher levels of glycerol were present in cheese, but not due to reuterin. Application of L. reuteri INIA P572 as adjunct to the commercial starter with 100 mM glycerol led to such a reuterin concentration in cheese that could control undesirable microorganisms, avoiding the presence of color-changing compounds.

Cool barnacles: Do common biogenic structures enhance or retard rates of deterioration of intertidal rocks and concrete?

Sedentary and mobile organisms grow profusely on hard substrates within the coastal zone and contribute to the deterioration of coastal engineering structures and the geomorphic evolution of rocky shores by both enhancing and retarding weathering and erosion. There is a lack of quantitative evidence for the direction and magnitude of these effects. This study assesses the influence of globally-abundant intertidal organisms, barnacles, by measuring the response of limestone, granite and marine-grade concrete colonised with varying percentage covers of Chthamalus spp. under simulated, temperate intertidal conditions. Temperature regimes at 5 and 10mm below the surface of each material demonstrated a consistent and statistically significant negative relationship between barnacle abundance and indicators of thermal breakdown. With a 95% cover of barnacles, subsurface peak temperatures were reduced by 1.59°C for limestone, 5.54°C for concrete and 5.97°C for granite in comparison to no barnacle cover. The amplitudes of short-term (15-30min) thermal fluctuations conducive to breakdown via 'fatigue' effects were also buffered by 0.70°C in limestone, 1.50°C in concrete and 1.63°C in granite. Furthermore, concentrations of potentially damaging salt ions were consistently lower under barnacles in limestone and concrete. These results indicate that barnacles do not enhance, but likely reduce rates of mechanical breakdown on rock and concrete by buffering near-surface thermal cycling and reducing salt ion ingress. In these ways, we highlight the potential role of barnacles as agents of bioprotection. These findings support growing international efforts to enhance the ecological value of hard coastal structures by facilitating their colonisation (where appropriate) through design interventions.

Accelerated stone deterioration induced by forest clearance around the Angkor temples

The present study provides the first quantitative assessment of the deteriorative impact of forest clearance on susceptible sandstone masonries. At Ta Keo, a 1000yr-old temple cleared of the Angkor forest in the early 20th century, GIS-based analysis of historic imagery indicates an average ten-fold increase in stone loss rates (0.2 instead of 0.02% per year). This accelerated decay is assigned to the climatic stress provoked by the exposure of fragile ornamented sandstones to the harsh impact of tropical sunshine and monsoon rains. Comparative climate monitoring with the Beng Mealea temple, still located in a forested environment, suggests a three-fold post-clearance increase in daily temperature and humidity ranges, which is conducive to enhanced swelling-shrinking movements responsible for accelerated sandstone contour scaling. Comparative visual assessment based on a customised 7-point scale of mechanical weathering confirms the protective role of canopy, with 79% of decorative motifs still almost free of mechanical weathering in the forest (against 7% at the cleared site). Disruption of archaeological structures by roots of individual trees can be locally observed at Angkor, but this does not negate the dominant overall buffering function of the forest cover. At Angkor and other cultural heritage sites, this bioprotective 'umbrella effect' should be considered as a valuable ecosystem service to be taken into account when defining and implementing strategies of sustainable management.