DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane) is probably the best known and most useful organochlorine insecticide in the world which was used since 1945 for agricultural purposes and also for vector-borne disease control such as malaria since 1955, until its banishment in most countries by the Stockholm convention for ecologic considerations. However, the World Health Organization allowed its reintroduction only for control of vector-borne diseases in some tropical countries in 2006. Due to its physicochemical properties and specially its persistence related with a half-life up to 30 years, DDT linked to several health and social problems which are due to its accumulation in the environment and its biomagnification properties in living organisms. This manuscript compiles a multidisciplinary review to evaluate primarily (i) the worldwide contamination of DDT and (ii) its (eco) toxicological impact onto living organisms. Secondly, several ways for DDT bioremediation from contaminated environment are discussed. For this, reports on DDT biodegradation capabilities by microorganisms and ways to enhance bioremediation strategies to remove DDT are presented. The different existing strategies for DDT bioremediation are evaluated with their efficiencies and limitations to struggle efficiently this contaminant. Finally, rising new approaches and technological bottlenecks to promote DDT bioremediation are discussed.
One of the main challenges of bioremediation is to define efficient protocols with low environmental impact and high removal rates, such as static magnetic field (SMF). The aim of this study was to evaluate the effect of SMF exposure on the biodegradation rate of a mixture of pollutants using three bacterial strains which were isolated and identified from the Bizerte lagoon: Pseudomonas stutzeri LBR (KC157911), Cupriavidus metallidurans LBJ (KU659610) and Rhodococcus equi LBB (KU743870). To recognize the improvement role of SMF, the culture was submitted to a pre-treatment with SMF with an induction equal to 200 mT for 5 hours, after that the degradation experiment was followed with individual strains and with a consortium. Results showed an increase by 20% in the growth of the exposed bacterial population compared to controls, and 98% of biodegradation of DDT and 90% for BaP after 30 days of follow-up. This encouraging data opens new perspectives for a bioremediation bioprocess using SMF.
Despite its antibacterial and antipathogenic effects, the heat treatment of milk induces undesirable changes that can be noted in the overall properties of ultrahigh temperature (UHT) milk, such as changes in nutritional and organoleptic properties. Our goal is to find new nonthermal antibacterial technologies for the preservation of raw milk (RM). This study investigates the possible synergistic effect of using a combination of the lactoperoxidase system (LS) and 3 g mL −1 of cinnamon essential oil (cinnamon EO) to inactivate the total flora of milk and Salmonella Hadar (S. Hadar). The LS was activated with 30 mg L −1 sodium percarbonate and 14 mg L −1 of sodium thiocyanate. Using this approach, we obtained a synergistic effect with a complete inhibition of the activity of the total flora of the milk and . Hadar after 12 hours at 25 ∘ C. In addition, the attainment of synergy was defined when the inhibitory effect of the two compounds together was greater than the effect observed by each compound added alone. Moreover, the monitoring of the synergistic effect at 4 ∘ C for 5 days showed complete inhibition of total flora for 3 days and for . Hadar it was up to 5 days. To summarize, the current study clearly identified a new inhibitory combination that may be used in food-based applications.
In this work, it was shown that activating the Lactoperoxidase system (LP system) has an antimicrobial effect against Salmonella enterica serovar Hadar (S. enterica Hadar), a foodborne pathogen widespread in Tunisia and therefore a major cause of gastroenteritis. The aim here was to optimize the concentrations of the various compounds used in activating the LP system and to test the efficiency of this optimized system on S. enterica Hadar growth. It was also demonstrated that using a single dose of activators (thiocyanate and percarbonate) was enough to obtain the antimicrobial effect of this system against S. enterica Hadar. Since lactoperoxidase has a broad antimicrobial spectrum, it can be used as an additional interesting way to improve food security in Tunisia and reduce the use of chemicals. It is possible to combine the LP system with bioactive molecules or introduce other nonthermal technologies for the bio-preservation of food. Within this context, it was shown that the antimicrobial effect of the LP system is inhibited in the presence of a concentration of 100 g / L of starch. The starch content in food should be taken into consideration when the LP system is applied in synergy with other natural conservation techniques.
The temperate bacteriophage Mu is a transposable element that can integrate randomly into bacterial DNA, thereby creating mutations. Mutants due to an integrated Mu prophage do not give rise to revertants, as if Mu, unlike other transposable elements, were unable to excise precisely. In the present work, starting with a lacZ::Muc62(Ts) strain unable to form Lac+ colonies, we cloned a lacZ+ gene in vivo on a mini-Mu plasmid, under conditions of prophage induction. In all lac+ plasmids recovered, the wild-type sequence was restored in the region where the Mu prophage had been integrated. The recovery of lacZ+ genes shows that precise excision of Mu does indeed take place; the absence of Lac+ colonies suggests that precise excision events are systematically associated with loss of colony-forming ability.
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