Influence of temperature, pH and NaCl concentration on the maximal growth rate of Brochothrix thermosphacta and a bioprotective bacteria Lactococcus piscium CNCM I-4031

On the benefits of desulfated seawater flooding in mature hydrocarbon fields

Removal of sulfate from the injection seawater (desulfation) in hydrocarbon reservoirs is a Modified Salinity Water (MSW) flooding method that mitigates microbial reservoir souring, improves oil recovery, and enables produced-water re-injection (PWRI). Aside from the Improved Oil Recovery (IOR) effect, desulfation results in a cleaner production of oil through enabling PWRI and reducing the environmental impacts associated with reservoir souring and nitrate treatment. However, whether desulfation is still beneficial for mature fields, after years of the injection of untreated seawater, is a valid common concern. In such cases, sulfate concentration inside the reservoir has already increased due to years of untreated seawater injection. The high sulfate concentration inside the subsurface reservoir before desulfated water flooding may render desulfation pointless. The present study investigates the potential benefits of desulfation after around 20 years of untreated seawater injection in a sector of an oil field in the Danish North Sea. The results show that depending on the cessation of production point in time and the efficiency of residual oil saturation reduction of MSW flooding, desulfation results in a significant increase in oil production. Even if improving oil recovery is no longer a priority, modification of injected seawater would still help reduce the amount of water required to support a given oil production rate. Moreover, desulfation is considerably more effective than nitrate treatment in mitigating microbial reservoir souring. Furthermore, the possibility of scale formation is decreased considerably due to desulfation, which further encourages PWRI.

Influence of the Carbon and Nitrogen Sources on Diabolican Production by the Marine Vibrio diabolicus Strain CNCM I-1629

Recent advances in glycobiotechnology show that bacterial exopolysaccharides (EPS) presenting glycosaminoglycan (GAG)-like properties can provide a valuable source of bio-active macromolecules for industrial applications. The HE800 EPS, named diabolican, is a marine-derived anionic high-molecular-weight polysaccharide produced by Vibrio diabolicus CNCM I-1629 which displays original structural features close to those of hyaluronic acid. We investigated the impact of carbon and nitrogen substrates on both Vibrio diabolicus growth and diabolican production. Both substrates were screened by a one-factor-at-a-time method, and experimental designs were used to study the effect of glucose, mannitol, and ammonium acetate various concentrations. Results showed that the medium composition affected not only the bacterium growth and EPS yield, but also the EPS molecular weight (MW). EPS yields of 563 and 330 mg L⁻¹ were obtained in the presence of 69.3 g L⁻¹ glucose and 24.6 g L⁻¹ mannitol, respectively, both for 116.6 mM ammonium acetate. MW was the highest, with 69.3 g L⁻¹ glucose and 101.9 mM ammonium acetate (2.3 × 10⁶ g mol⁻¹). In parallel, the bacterial maximum specific growth rate was higher when both carbon and nitrogen substrate concentrations were low. This work paves the way for the optimization of marine exopolysaccharide production of great interest in the fields of human health and cosmetics.

To culture or not to culture: careful assessment of metabarcoding data is necessary when evaluating the microbiota of a modified-atmosphere-packaged vegetarian meat alternative throughout its shelf-life period

Background

As the increased consumption of ready-to-eat meat alternatives is a fairly recent trend, little is known about the composition and dynamics of the microbiota present on such products. Such information is nonetheless valuable in view of spoilage and food safety prevention. Even though refrigeration and modified-atmosphere-packaging (MAP) can extend the shelf-life period, microbial spoilage can still occur in these products. In the present study, the microbiota of a vegetarian alternative to poultry-based charcuterie was investigated during storage, contrasting the use of a culture-dependent method to a culture-independent metagenetic method.

Results

The former revealed that lactic acid bacteria (LAB) were the most abundant microbial group, specifically at the end of the shelf-life period, whereby Latilactobacillus sakei was the most abundant species. Metabarcoding analysis, in contrast, revealed that DNA of Xanthomonas was most prominently present, which likely was an artifact due to the presence of xanthan gum as an ingredient, followed by Streptococcus and Weissella.

Conclusions

Taken together, these results indicated that Lb. sakei was likely the most prominent specific spoilage organisms (SSO) and, additionally, that the use of metagenetic analysis needs to be interpreted with care in this specific type of product. In order to improve the performance of metagenetics in food samples with a high DNA matrix but a low bacterial DNA load, selective depletion techniques for matrix DNA could be explored.

Development of a rapid qPCR method to quantify lactic acid bacteria in cold-smoked salmon

Quantification of lactic acid bacteria (LAB) is essential to control quality of seafood products like cold-smoked salmon (CSS). In the present study, we report the design and optimization of a dual-labelled TaqMan ™ probe targeting the V7 region of 16S rRNA gene for the detection of LAB in CSS. This quantitative PCR (qPCR) assays is useful for the simultaneous detection of the ten LAB genera communally encountered in CSS as Aerococcus, Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Macrococcus, Streptococcus, Vagococcus and Weissella. The specificity of this method was demonstrated against 14 genera (44 isolates, 35 species) of Gram-positive bacteria and 19 genera of Gram-negative (40 isolates, 34 species). Calibration of the method was performed in CSS matrix using a mix of equimolar cultured solution of five LAB. Quantification with the qPCR method range from 3.5 to 8.5 Log CFU/g in CSS matrix, covering 5 orders of magnitude. On these artificially contaminated CSS slices, PCR method results correlated successfully (R² = 0.9945) with the conventional enumeration on Elliker medium. In addition, the new method was successful on commercial CSS from five different origins with a quantification range from 3.7 Log CFU/g to 8.0 Log CFU/g. This one-step quantitative methodology is proposed as a rapid and complementary tool of the cultural methods to investigate the LAB microbiota and biodiversity of CSS.

The effect of pH on the growth rate of Bacillus cereus sensu lato: Quantifying strain variability and modelling the combined effects of temperature and pH

In this study, the effect of pH, alone or in combination with temperature, on the maximum growth rate (μ_max) of B. cereus sensu lato was investigated. In phase 1, the effect of pH at 30 °C was studied for 16 mesophilic strains and 2 psychrotrophic strains of Bacillus cereus sensu lato. The μ_max vs. pH relationship was found to show a similar pattern for all the strains. Several pH models from literature were evaluated and the best performing 'growth rate vs. pH' model selected. A stochastic model was then developed to predict the maximum specific growth rate of mesophilic B. cereus at 30 °C as a function of pH, the intra-species variability being incorporated via considering the model parameters (e.g. pH_min) randomly distributed. The predicted maximum specific growth rates were acceptably close to independent published data. In phase 2, the combined effects of temperature and pH were studied. Growth rates were also generated at 15, 20 and 40 °C for a selection of strains and the pH model was fitted at each temperature. Interestingly, the results showed that the estimates for the pH_min parameter for mesophilic strains were lower at 20-30 °C than near the optimum temperature (40 °C), suggesting that experiments for the determination of this parameter should be conducted at lower-than-optimum temperatures. New equations were proposed for the relationship between temperature and the minimum pH-values, which were also consistent with the experimental growth boundaries. The parameters defining this equation quantify the minimum temperature for growth observed experimentally, the temperature of maximum enzyme stability and the maximum temperature for growth. Deviations from the Gamma hypothesis (multiplicative effects of environmental factors on the maximum specific growth rate) were observed near the growth limits, especially at 40 °C. To improve model performance, two approaches, one based on a minimum pH-term (doi: https://doi.org/10.3389/fmicb.2019.01510) and one based on an interaction term (doi: http://dx.doi.org/10.1016/S0168-1605(01)00640-7) were evaluated.

The pathogenic and spoilage bacteria associated with red meat and application of different approaches of high CO2 packaging to extend product shelf-life

With the fast-global development of packaging techniques, the potential antimicrobial effect of CO₂, as a safe, cheap and readily available gas, makes it the integral component for packaging of meat products. The associated spoilage and/or pathogenic bacteria on raw meat may respond in different ways to elevated CO₂ concentrations. The growth of some aerobic Gram-negative bacteria such as Pseudomonas spp. is significantly inhibited but some LAB bacteria may be allowed to grow faster and dominate the product. The antimicrobial efficacy of enriched CO₂ packaging is attributed to the rate of CO₂ solubility in the product which is itself affected by the level of headspace CO₂, product pH, temperature and the ratio of headspace gas to product (G:P). This review, first, explores the varied range of beef and sheep meat spoilage and pathogenic bacteria and the intrinsic and extrinsic parameters that may influence the pattern of microbial growth and meat spoilage rate during storage. Then, the antimicrobial mechanism of elevated CO₂ packaging will be discussed and the different approaches of achieving enriched CO₂ packaging i.e. the traditional technique of flushing a desired gas mixture and/or using the new commercially developed CO₂ emitters will then be compared in terms of their strengths, limitations and technical mode of action.

Evaluation of Biocompatibility and Antagonistic Properties of Microorganisms Isolated from Natural Sources for Obtaining Biofertilizers Using Microalgae Hydrolysate

Determination of the biocompatibility of microorganisms isolated from natural sources (Kemerovo Oblast—Kuzbass) resulted in the creation of three microbial consortia based on the isolated strains: consortium I (Bacillus pumilus, Pediococcus damnosus, and Pediococcus pentosaceus), consortium II (Acetobacter aceti, Pseudomonas chlororaphis, and Streptomyces parvus), and consortium III (Amycolatopsis sacchari, Bacillus stearothermophilus; Streptomyces thermocarboxydus; and Streptomyces thermospinisporus). The nutrient media composition for the cultivation of each of the three studied microbial consortia, providing the maximum increase in biomass, was selected: consortium I, nutrient medium 11; consortium II, nutrient medium 13; for consortium III, nutrient medium 16. Consortia I and II microorganisms were cultured at 5–25 °C, and consortium III at 50–70 °C. Six types of psychrophilic microorganisms (P. pentosaceus, P. chlororaphis, P. damnosus, B. pumilus, A. aceti, and S. parvus) and four types of thermophilic microorganisms (B. stearothermophilus, S. thermocarboxydus, S. thermospinisporus, and A. sacchari) were found to have high antagonistic activity against the tested pathogenic strains (A. faecalis, B. cinerea, E. carotovora, P. aeruginosa, P. fluorescens, R. stolonifera, X. vesicatoria. pv. Vesicatoria, and E. aphidicola). The introduction of microalgae hydrolyzate increased the concentration of microorganisms by 5.23 times in consortium I, by 4.66 times in consortium II, by 6.6 times in consortium III. These data confirmed the efficiency (feasibility) of introducing microalgae hydrolyzate into the biofertilizer composition.

Simulation-Based Optimization of Microbial Enhanced Oil Recovery with a Model Integrating Temperature, Pressure, and Salinity Effects

The microbial enhanced oil recovery (MEOR) method is an eco-friendly and economical alternative technology. The technology involves a variety of uncertainties, and its success depends on controlling microbial growth and metabolism. Though a few numerical studies have been carried out to reduce the uncertainties, no attempt has been made to consider temperature, pressure, and salinity in an integrated manner. In this study, a new modeling method incorporating these environmental impacts was proposed, and MEOR analysis was performed. As a result, accurate modeling was possible to prevent overestimating the performance of MEOR. In addition, oil recovery was maximized through sensitivity analysis and optimization based on an integrative model. Finally, applying MEOR to an actual reservoir model showed a 7% increase in oil recovery compared to waterflooding. This result proved the practical applicability of the method.

Effect of glucose, pH and lactic acid on Carnobacterium maltaromaticum, Brochothrix thermosphacta and Serratia liquefaciens within a commercial heat-shrunk vacuum-package film

Carnobacterium maltaromaticum, Brochothrix thermosphacta and Serratia liquefaciens are common spoilage organisms found within the microbiome of refrigerated vacuum-packaged (VP) beef. Extending and predicting VP beef shelf-life requires knowledge about how spoilage bacteria growth is influenced by environmental extrinsic and intrinsic factors. Multifactorial effects of pH, lactic acid (LA) and glucose on growth kinetics were quantified for C. maltaromaticum, B. thermosphacta and S. liquefaciens within a heat shrink-wrapped VP commercial film containing a simulated beef medium. LA, pH, and undissociated lactic acid (UDLA) significantly affected bacterial growth rate (p < 0.001), whereas 5.55 mM glucose produced a marginal effect. At 1.12 mM UDLA, growth rate and maximum population density decreased 20.9 and 3.5%, 56 and 7%, and 11 and 2% for C. maltaromaticum, B. thermosphacta, and S. liquefaciens, respectively.

Modeling the Growth and Interaction Between Brochothrix thermosphacta, Pseudomonas spp., and Leuconostoc gelidum in Minced Pork Samples

The aim of this study was to obtain the growth parameters of specific spoilage micro-organisms previously isolated in minced pork (MP) samples and to develop a three-spoilage species interaction model under different storage conditions. Naturally contaminated samples were used to validate this approach by considering the effect of the food microbiota. Three groups of bacteria were inoculated on irradiated samples, in mono- and in co-culture experiments (n = 1152): Brochothrix thermosphacta, Leuconostoc gelidum, and Pseudomonas spp. (Pseudomonas fluorescens and Pseudomonas fragi). Samples were stored in two food packaging [food wrap and modified atmosphere packaging (CO2 30%/O2 70%)] at three isothermal conditions (4, 8, and 12°C). Analysis was carried out by using both 16S rRNA gene amplicon sequencing and classical microbiology in order to estimate bacterial counts during the storage period. Growth parameters were obtained by fitting primary (Baranyi) and secondary (square root) models. The food packaging shows the highest impact on bacterial growth rates, which in turn have the strongest influence on the shelf life of food products. Based on these results, a three-spoilage species interaction model was developed by using the modified Jameson-effect model and the Lotka Volterra (prey-predator) model. The modified Jameson-effect model showed slightly better performances, with 40-86% out of the observed counts falling into the Acceptable Simulation Zone (ASZ). It only concerns 14-48% for the prey-predator approach. These results can be explained by the fact that the dynamics of experimental and validation datasets seems to follow a Jameson behavior. On the other hand, the Lotka Volterra model is based on complex interaction factors, which are included in highly variable intervals. More datasets are probably needed to obtained reliable factors, and so better model fittings, especially for three- or more-spoilage species interaction models. Further studies are also needed to better understand the interaction of spoilage bacteria between them and in the presence of natural microbiota.

Extended antibiotic treatment in salmon farms select multiresistant gut bacteria with a high prevalence of antibiotic resistance genes

The high use of antibiotics for the treatment of bacterial diseases is one of the main problems in the mass production of animal protein. Salmon farming in Chile is a clear example of the above statement, where more than 5,500 tonnes of antibiotics have been used over the last 10 years. This has caused a great impact both at the production level and on the environment; however, there are still few works in relation to it. In order to demonstrate the impact of the high use of antibiotics on fish gut microbiota, we have selected four salmon farms presenting a similar amount of fish of the Atlantic salmon species (Salmo salar), ranging from 4,500 to 6,000 tonnes. All of these farms used treatments with high doses of antibiotics. Thus, 15 healthy fish were selected and euthanised in order to isolate the bacteria resistant to the antibiotics oxytetracycline and florfenicol from the gut microbiota. In total, 47 bacterial isolates resistant to florfenicol and 44 resistant to oxytetracycline were isolated, among which isolates with Minimum Inhibitory Concentrations (MIC) exceeding 2048 μg/mL for florfenicol and 1024 μg/mL for oxytetracycline were found. In addition, another six different antibiotics were tested in order to demonstrate the multiresistance phenomenon. In this regard, six isolates of 91 showed elevated resistance values for the eight tested antibiotics, including florfenicol and oxytetracycline, were found. These bacteria were called “super-resistant” bacteria. This phenotypic resistance was verified at a genotypic level since most isolates showed antibiotic resistance genes (ARGs) to florfenicol and oxytetracycline. Specifically, 77% of antibiotic resistant bacteria showed at least one gene resistant to florfenicol and 89% showed at least one gene resistant to oxytetracycline. In the present study, it was demonstrated that the high use of the antibiotics florfenicol and oxytetracycline has, as a consequence, the selection of multiresistant bacteria in the gut microbiota of farmed fish of the Salmo salar species at the seawater stage. Also, the phenotypic resistance of these bacteria can be correlated with the presence of antibiotic resistance genes.

Effect of pomegranate based marinades on the microbiological, chemical and sensory quality of chicken meat: A metabolomics approach

Pomegranate juice is a product with enhanced functional properties that could be used as an alternative to traditional marination ingredients and effectively retard microbial growth along with providing an improved sensory result. In this study, two pomegranate based marinades were prepared for the marination of chicken breast fillets and the marinated samples were aerobically stored at 4 and 10°C for 9days. Raw, non-marinated chicken samples were used as control. Levels of total viable counts (TVC), Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae and lactic acid bacteria (LAB) were determined together with sensory assessment to evaluate the evolution of spoilage. The profile of organic acids and volatile compounds was also analyzed during storage. The shelf life of marinated samples was significantly extended compared to control samples at both storage temperatures (e.g., up to 5 and 6days for the pomegranate/lemon marinated samples stored at 4 and 10°C, respectively) as evaluated by both microbiological and sensory analyses. The profile of the organic acids and the volatilome of marinated and control samples were remarkably differentiated according to storage time, microbial load and sensory score. The findings of this study suggest that pomegranate juice could be used as a novel ingredient in marinades to improve the sensory attributes, while prolonging the shelf life of chicken meat.

Mechanistic modelling of the inhibitory effect of pH on microbial growth

Modelling and simulation of microbial dynamics as a function of processing, transportation and storage conditions is a useful tool to improve microbial food safety and quality. The goal of this research is to improve an existing methodology for building mechanistic predictive models based on the environmental conditions. The effect of environmental conditions on microbial dynamics is often described by combining the separate effects in a multiplicative way (gamma concept). This idea was extended further in this work by including the effects of the lag and stationary growth phases on microbial growth rate as independent gamma factors. A mechanistic description of the stationary phase as a function of pH was included, based on a novel class of models that consider product inhibition. Experimental results on Escherichia coli growth dynamics indicated that also the parameters of the product inhibition equations can be modelled with the gamma approach. This work has extended a modelling methodology, resulting in predictive models that are (i) mechanistically inspired, (ii) easily identifiable with a limited work load and (iii) easily extended to additional environmental conditions.

Lactococcus piscium: a psychrotrophic lactic acid bacterium with bioprotective or spoilage activity in food-a review

The genus Lactococcus comprises 12 species, some known for decades and others more recently described. Lactococcus piscium, isolated in 1990 from rainbow trout, is a psychrotrophic lactic acid bacterium, probably disregarded because most of the strains are unable to grow at 30°C. During the last 10 years, this species has been isolated from a large variety of food: meat, seafood and vegetables, mostly packed under vacuum (VP) or modified atmosphere (MAP) and stored at chilled temperature. Recently, culture-independent techniques used for characterization of microbial ecosystems have highlighted the importance of Lc. piscium in food. Its role in food spoilage varies according to the strain and the food matrix. However, most studies have indicated that Lc. piscium spoils meat, whereas it does not degrade the sensory properties of seafood. Lactococcus piscium strains have a large antimicrobial spectrum, including Gram-positive and negative bacteria. In various seafoods, some strains have a protective effect against spoilage and can extend the sensory shelf-life of the products. They can also inhibit the growth of Listeria monocytogenes, by a cell-to-cell contact-dependent. This article reviews the physiological and genomic characteristics of Lc. piscium and discusses its spoilage or protective activities in food.

Introducing a novel interaction model structure for the combined effect of temperature and pH on the microbial growth rate

Efficient modelling of the microbial growth rate can be performed by combining the effects of individual conditions in a multiplicative way, known as the gamma concept. However, several studies have illustrated that interactions between different effects should be taken into account at stressing environmental conditions to achieve a more accurate description of the growth rate. In this research, a novel approach for modeling the interactions between the effects of environmental conditions on the microbial growth rate is introduced. As a case study, the effect of temperature and pH on the growth rate of Escherichia coli K12 is modeled, based on a set of computer controlled bioreactor experiments performed under static environmental conditions. The models compared in this case study are the gamma model, the model of Augustin and Carlier (2000), the model of Le Marc et al. (2002) and the novel multiplicative interaction model, developed in this paper. This novel model enables the separate identification of interactions between the effects of two (or more) environmental conditions. The comparison of these models focuses on the accuracy, interpretability and compatibility with efficient modeling approaches. Moreover, for the separate effects of temperature and pH, new cardinal parameter model structures are proposed. The novel interaction model contributes to a generic modeling approach, resulting in predictive models that are (i) accurate, (ii) easily identifiable with a limited work load, (iii) modular, and (iv) biologically interpretable.

Heterotrophic microflora of highly alkaline (pH > 13) brown mud disposal site drainage water near Ziar nad Hronom (Banska Bystrica region, Slovakia)

Brown mud is a waste by-product of alumina production by Bayer process. Due to extensive sodium hydroxide use in the process, brown mud disposal site near Ziar nad Hronom (Banska Bystrica region, Slovakia) and drainage water are ones of the greatest environmental burdens in Slovakia. Drainage water from this landfills has pH value higher than 13, and it contains many heavy metals and elevated salt content. In our experiments, relatively numerous bacterial population was detected in the drainage water with frequency of about 80 cfu/ml using cultivation approach. The alkalitolerant heterotrophic isolates were identified by combination of MALDI-TOF and 16S rDNA analysis. Drainage water population was dominated by Actinobacteria (Microbacterium spp. and Micrococcus spp.) followed by low G + C-content gram-positive bacteria (Bacillus spp.). Two isolates belonged to gram-negative bacteria only, identified as Brevundimonas spp. Phylogenetic and biochemical analyses indicate that nearly half of the bacteria isolated are probably representatives of a new species. Brown mud disposal site is proposed as a source of new bacterial taxa possibly used in bioremediation processes.

Modelling the effect of lactic acid bacteria from starter- and aroma culture on growth of Listeria monocytogenes in cottage cheese

Four mathematical models were developed and validated for simultaneous growth of mesophilic lactic acid bacteria from added cultures and Listeria monocytogenes, during chilled storage of cottage cheese with fresh- or cultured cream dressing. The mathematical models include the effect of temperature, pH, NaCl, lactic- and sorbic acid and the interaction between these environmental factors. Growth models were developed by combining new and existing cardinal parameter values. Subsequently, the reference growth rate parameters (μref at 25°C) were fitted to a total of 52 growth rates from cottage cheese to improve model performance. The inhibiting effect of mesophilic lactic acid bacteria from added cultures on growth of L. monocytogenes was efficiently modelled using the Jameson approach. The new models appropriately predicted the maximum population density of L. monocytogenes in cottage cheese. The developed models were successfully validated by using 25 growth rates for L. monocytogenes, 17 growth rates for lactic acid bacteria and a total of 26 growth curves for simultaneous growth of L. monocytogenes and lactic acid bacteria in cottage cheese. These data were used in combination with bias- and accuracy factors and with the concept of acceptable simulation zone. Evaluation of predicted growth rates of L. monocytogenes in cottage cheese with fresh- or cultured cream dressing resulted in bias-factors (Bf) of 1.07-1.10 with corresponding accuracy factor (Af) values of 1.11 to 1.22. Lactic acid bacteria from added starter culture were on average predicted to grow 16% faster than observed (Bf of 1.16 and Af of 1.32) and growth of the diacetyl producing aroma culture was on average predicted 9% slower than observed (Bf of 0.91 and Af of 1.17). The acceptable simulation zone method showed the new models to successfully predict maximum population density of L. monocytogenes when growing together with lactic acid bacteria in cottage cheese. 11 of 13 simulations of L. monocytogenes growth were within the acceptable simulation zone, which demonstrated good performance of the empirical inter-bacterial interaction model. The new set of models can be used to predict simultaneous growth of mesophilic lactic acid bacteria and L. monocytogenes in cottage cheese during chilled storage at constant and dynamic temperatures. The applied methodology is likely to be applicable for safety prediction of other types of fermented and unripened dairy products where inhibition by lactic acid bacteria is important for growth of pathogenic microorganisms.

Characterization of Carnobacterium maltaromaticum LMA 28 for its positive technological role in soft cheese making

Carnobacterium maltaromaticum is a lactic acid bacterium isolated from soft cheese. The objective of this work was to study its potential positive impact when used in cheese technology. Phenotypic and genotypic characterization of six strains of C. maltaromaticum showed that they belong to different phylogenetic groups. Although these strains lacked the ability to coagulate milk quickly, they were acidotolerant. They did not affect the coagulation capacity of starter lactic acid bacteria, Lactococcus lactis and Streptococcus thermophilus, used in dairy industry. The impact of C. maltaromaticum LMA 28 on bacterial flora of cheese revealed a significant decrease of Psychrobacter sp. concentration, which might be responsible for cheese aging phenomena. An experimental plan was carried out to unravel the mechanism of inhibition of Psychrobacter sp. and Listeria monocytogenes and possible interaction between various factors (cell concentration, NaCl, pH and incubation time). Cellular concentration of C. maltaromaticum LMA 28 was found to be the main factor involved in the inhibition of Psychrobacter sp. and L. monocytogenes.