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Aouadhi C.,Pasteur Institute of Tunisia IPT | Aouadhi C.,University of Nantes | Aouadhi C.,French National Center for Scientific Research | Aouadhi C.,National Institute of Agronomy | And 8 more authors.
Food Microbiology | Year: 2012

Bacillus sporothermodurans produces highly resistant endospores that can survive ultra-high-temperature treatment in milk. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk sterility. In this work, the rate of spore germination of B.sporothermodurans LTIS27 was measured in distilled water after high-pressure treatments with varying pressure (50-600MPa), treatment temperature (20-50°C), pressure-holding time (5-30min) and post-pressurization incubation time (30-120min) at 37°C or 4°C. The results showed that pressure-induced germination was maximal (62%) after a treatment at 200MPa and 20°C and increased with pressure-holding time and post-pressurization incubation time. Treatment temperature had no significant effect on germination. A central composite experimental design with three factors (pressure, pressure-holding time, and post-pressurization incubation time) using response surface methodology was used to optimize the germination rate in distilled water and in skim milk. No factor interaction was observed. Germination was induced at lower pressure and was faster in milk than in distilled water, but complete germination was not reached. The optimum germination obtained with experimental data was 5.0logcfu/mL in distilled water and 5.2logcfu/mL in milk from 5.7logcfu/mL of spores initially present in the suspension. This study shows the potential of using high hydrostatic pressure to induce the germination of B.sporothermodurans spores in milk before a heat treatment. © 2011 Elsevier Ltd.


Aouadhi C.,Pasteur Institute of Tunisia IPT | Aouadhi C.,University of Nantes | Aouadhi C.,French National Center for Scientific Research | Aouadhi C.,National Institute of Agronomy | And 8 more authors.
LWT - Food Science and Technology | Year: 2013

Bacillus sporothermodurans is a milk spoilage bacterium producing resistant endospores that survive ultra-high temperature treatment. The inactivation of B. sporothermodurans LTIS27 spores by combined hydrostatic pressure and heat treatments was studied. A central composite experimental design was used to evaluate the effect of pressure (300-500 MPa), temperature (30-50 °C), and pressure-holding time (10-30 min) on the inactivation of spores in distilled water and skim milk. The inactivation observed was shown to fit well with the values predicted by the quadratic equation, since R adj 2 were 0.970 and 0.977 in distilled water and milk, respectively. By analyzing the response surface plots, the inactivation was shown to be higher in distilled water than in milk under all the conditions tested. This was probably due to a protective effect of milk against inactivation by pressure. The optimum process parameter values for a 5-log cycle reduction of spores were calculated as 477 MPa/48 °C for 26 min and 495 MPa/49 °C for 30 min in water and in milk, respectively. This study shows the efficiency of hydrostatic pressure in combination with moderate temperature to inactivate B. sporothermodurans spores. Such treatments could be applied by the dairy industry to ensure the commercial sterility of UHT milk. © 2012 Elsevier Ltd.


PubMed | Tunis el Manar University, National Water Research Institute, Jendouba University, Pasteur Institute of Tunisia IPT and Center de Biotechnologie de la Technopole de Borj-Cedria
Type: Journal Article | Journal: Chemistry & biodiversity | Year: 2016

In the current study, the phenolic composition, antioxidant and antimicrobial activities of extracts from Rubus ulmifolius Schott leaves harvested in four localities (Sejnen, Tabarka, Faija and Ain drahem) in Tunisia were investigated for the first time. Great differences were found for the chemical composition, total phenol contents and biological activities among the evaluated extracts. HPLC analysis of methanolic extracts showed that the dominant compounds were kaempferol 3-O-rutinoside and naringenine. In addition, significant correlations were observed between antioxidant activities and phenolic contents. In fact, leaves collected from Sejnen presented higher total phenol content (53.32 mg GAE/g DW) and antioxidant activities (IC


Aouadhi C.,Pasteur Institute of Tunisia IPT | Aouadhi C.,University of Nantes | Aouadhi C.,French National Center for Scientific Research | Aouadhi C.,National Institute of Agronomy Tunis INAT | And 4 more authors.
Food Microbiology | Year: 2013

Spores of Bacillus sporothermodurans are known to be contaminant of dairy products and to be extremely heat-resistant. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk stability. In this study, the nutrient-induced germination of B.sporothermodurans LTIS27 spores was studied. Testing the effect of 23 nutrient elements to trigger an important germination rate of B.sporothermodurans spores, only d-glucose, l-alanine, and inosine were considered as strong independent germinants. Both inosine and l-alanine play major roles as co-germinants with several other amino acids. A central composite experimental design with three factors (l-alanine, d-glucose, and temperature) using response surface methodology was used to optimize the nutrient-induced germination. The optimal rate of nutrient-induced germination (100%) of B.sporothermodurans spores was obtained after incubation of spore for 60min at 35°C in presence of 9 and 60mM of d-glucose and l-alanine, respectively. The results in this study can help to predict the effect of environmental factors and nutrients on spore germination, which will be beneficial for screening of B.sporothermodurans in milk after induction their germination. Moreover, the chosen method of optimization of the nutrient-induced germination was efficient in finding the optimum values of three factors. © 2013 Elsevier Ltd.


Aouadhi C.,Pasteur Institute of Tunisia IPT | Aouadhi C.,National Institute of Agronomy | Rouissi Z.,Pasteur Institute of Tunisia IPT | Kmiha S.,Pasteur Institute of Tunisia IPT | And 2 more authors.
Food Microbiology | Year: 2016

Bacillus sporothermodurans cells were grown in various environmental conditions to study the effects of temperature, pH, and water activity of the sporulation medium on spore inactivation by nisin and heat treatment. The obtained results showed that the modification of the sporulation conditions affected the spore properties. In fact, the resistance of B. sporothermodurans spores to heat treatment combined with nisin (treatment at 95 °C for 12 min in the presence of 125 UI/ml) increases with increasing of pH level (7-9) and decreases as the acidity of the medium increases. While the sensitivity of B. sporothermodurans spores depends on the sporulation temperature. It increases with increasing the temperature from 4 to 37 °C, but starting with 42 °C, the sensitivity decreases. In the presence of NaCl as depressor, the resistance of B. sporothermodurans spores was higher compared with standard conditions (pH 7, 37 °C without NaCl or glycerol) with an inactivation rate does not exceed 2.79 log. This is the first study which contributed to understand the relationship between the sporulation conditions (pH, temperature and water activity) and the resistance of B. sporothermodurans spores to nisin and heat treatment. It shows that the sporulation conditions, particularly sporulation temperature, must be carefully taken into account during settling sterilization processes applied in the dairy industry. © 2015 Elsevier Ltd.


Aouadhi C.,Pasteur Institute of Tunisia IPT | Aouadhi C.,National Institute of Agronomy | Rouissi Z.,Pasteur Institute of Tunisia IPT | Mejri S.,National Institute of Agronomy | Maaroufi A.,Pasteur Institute of Tunisia IPT
Food Microbiology | Year: 2014

Spores of Bacillus sporothermodurans are known to be a contaminant of dairy products and to be extremely heat-resistant. A central composite experimental design with three factors using response surface methodology was used to evaluate the effect of nisin (50-150UI/mL), temperature (80-100°C), and temperature-holding time (10-20min) on the inactivation of B.sporothermodurans LTIS27 spores in distilled water, in skim milk and in chocolate milk. The experimental values were shown to be significantly in good agreement with the values predicted by the quadratic equation since the adjusted determination coefficients (Radj 2) were around 0.97. By analyzing the response surfaces plots, the inactivation was shown to be higher in distilled water than in skim milk under all the conditions tested. Five-log cycle reductions of B.sporothermodurans spores were obtained after a treatment at 95°C for 12min in presence of 125UI of nisin/mL in distilled water or at 100°C for 13min in presence of 134UI of nisin/mL in skim milk or at 100°C for 15min in presence of 135UI of nisin/mL in chocolate milk. This study showed the efficiency of nisin (15-184UI/mL) in combination with temperature (73-106°C) to inactivate spores of B.sporothermodurans in milk. © 2013 Elsevier Ltd.


Mezni F.,National Water Research Institute | Shili S.,Pasteur Institute of Tunisia IPT | Ben Ali N.,Pasteur Institute of Tunisia IPT | Larbi Khouja M.,National Water Research Institute | And 2 more authors.
Pharmaceutical Biology | Year: 2016

Context: Within the global context of increasing cancer diseases, natural products are important in devising new drugs and providing unique ideas in cancer therapy. In Tunisian folk medicine, Pistacia lentiscus L. (Anacardiaceae) fixed oil is used for cancer treatment.Objective: This investigation studied, for the first time, the antiproliferative effect of Pistacia lentiscus fixed oil and its phenolic extract on BHK21 cancer cells.Materials and methods: Oil was extracted from fruits harvested in northwest Tunisia and the phenolic fraction was obtained by mixing with methanol. The anti-proliferative activity of the two tested substances on BHK 21 cells were investigated in vitro using trypan blue assays. Cells were treated with different concentrations of P. lentiscus oil (0.009, 0.018, 0.036, and 0.09 g/mL) and the phenolic extract (0.007, 0.014, 0.03, and 0.07 g/mL) for 24, 48, and 72 h.Results: The inhibitory effect of Pistacia lentiscus fixed oil increases with the increase in dose. The IC50 value was estimated at 0.029 g/mL. The percentage of cell viability was 42.46 ± 3.4% at a dose of 0.09 g/mL and was significantly lower than that of the untreated control (96.24 ± 2.5%, p<0.01). The phenolic extract demonstrated a dose- and time-dependent inhibitory effect on BHK21 cell growth. After 48 h of incubation, the IC50 value was estimated at 0.15 g/mL.Discussion and conclusion: The results demonstrated the potential of Pistacia lentiscus fixed oil in treating cancer, as it is used in traditional medicine. © 2015 Taylor & Francis.


PubMed | National Water Research Institute and Pasteur Institute of Tunisia IPT
Type: Journal Article | Journal: Pharmaceutical biology | Year: 2016

Within the global context of increasing cancer diseases, natural products are important in devising new drugs and providing unique ideas in cancer therapy. In Tunisian folk medicine, Pistacia lentiscus L. (Anacardiaceae) fixed oil is used for cancer treatment.This investigation studied, for the first time, the antiproliferative effect of Pistacia lentiscus fixed oil and its phenolic extract on BHK21 cancer cells.Oil was extracted from fruits harvested in northwest Tunisia and the phenolic fraction was obtained by mixing with methanol. The anti-proliferative activity of the two tested substances on BHK 21 cells were investigated in vitro using trypan blue assays. Cells were treated with different concentrations of P. lentiscus oil (0.009, 0.018, 0.036, and 0.09 g/mL) and the phenolic extract (0.007, 0.014, 0.03, and 0.07 g/mL) for 24, 48, and 72 h.The inhibitory effect of Pistacia lentiscus fixed oil increases with the increase in dose. The IC50 value was estimated at 0.029 g/mL. The percentage of cell viability was 42.46 3.4% at a dose of 0.09 g/mL and was significantly lower than that of the untreated control (96.24 2.5%, p<0.01). The phenolic extract demonstrated a dose- and time-dependent inhibitory effect on BHK21 cell growth. After 48 h of incubation, the IC50 value was estimated at 0.15 g/mL.The results demonstrated the potential of Pistacia lentiscus fixed oil in treating cancer, as it is used in traditional medicine.


PubMed | Pasteur Institute of Tunisia IPT
Type: | Journal: Food microbiology | Year: 2013

Spores of Bacillus sporothermodurans are known to be a contaminant of dairy products and to be extremely heat-resistant. A central composite experimental design with three factors using response surface methodology was used to evaluate the effect of nisin (50-150UI/mL), temperature (80-100C), and temperature-holding time (10-20min) on the inactivation of B.sporothermodurans LTIS27 spores in distilled water, in skim milk and in chocolate milk. The experimental values were shown to be significantly in good agreement with the values predicted by the quadratic equation since the adjusted determination coefficients (Radj(2)) were around 0.97. By analyzing the response surfaces plots, the inactivation was shown to be higher in distilled water than in skim milk under all the conditions tested. Five-log cycle reductions of B.sporothermodurans spores were obtained after a treatment at 95C for 12min in presence of 125UI of nisin/mL in distilled water or at 100C for 13min in presence of 134UI of nisin/mL in skim milk or at 100C for 15min in presence of 135UI of nisin/mL in chocolate milk. This study showed the efficiency of nisin (15-184UI/mL) in combination with temperature (73-106C) to inactivate spores of B.sporothermodurans in milk.


PubMed | Pasteur Institute of Tunisia IPT
Type: Journal Article | Journal: Food microbiology | Year: 2013

Spores of Bacillus sporothermodurans are known to be contaminant of dairy products and to be extremely heat-resistant. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk stability. In this study, the nutrient-induced germination of B. sporothermodurans LTIS27 spores was studied. Testing the effect of 23 nutrient elements to trigger an important germination rate of B. sporothermodurans spores, only D-glucose, L-alanine, and inosine were considered as strong independent germinants. Both inosine and L-alanine play major roles as co-germinants with several other amino acids. A central composite experimental design with three factors (L-alanine, D-glucose, and temperature) using response surface methodology was used to optimize the nutrient-induced germination. The optimal rate of nutrient-induced germination (100%) of B. sporothermodurans spores was obtained after incubation of spore for 60 min at 35 C in presence of 9 and 60 mM of D-glucose and L-alanine, respectively. The results in this study can help to predict the effect of environmental factors and nutrients on spore germination, which will be beneficial for screening of B. sporothermodurans in milk after induction their germination. Moreover, the chosen method of optimization of the nutrient-induced germination was efficient in finding the optimum values of three factors.

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