Microbiological parameters and maturity degree during composting of Posidonia oceanica residues mixed with vegetable wastes in semi-arid pedo-climatic condition

The aim of this study was to characterize the biological stability and maturity degree of compost during a controlled pile-composting trial of mixed vegetable residues (VR) collected from markets of Tunis City with residues of Posidonia oceanica (PoR), collected from Tunis beaches. The accumulation in beaches (as well as their removal) constitutes a serious environmental problem in all Mediterranean countries particularly in Tunisia. Aerobic-thermophilic composting is the most reasonable way to profit highly-valuable content of organic matter in these wastes for agricultural purposes. The physical, chemical, and biological parameters were monitored during composting over 150 d. The most appropriate parameters were selected to establish the maturity degree. The main result of this research was the deduction of the following maturity criterion: (a) C/N ratio < 15; (b) NH₄⁺-N < 400 mg/kg; (c) CO₂-C < 2000 mg CO₂-C/kg; (d) dehydrogenase activity < 1 mg TPF/g dry matter; (e) germination index (GI) > 80%. These five parameters, considered jointly are indicative of a high maturity degree and thus of a high-quality organic amendment which employed in a rational way, may improve soil fertility and soil quality. The mature compost was relatively rich in N (13.0 g/kg), P (4.74 g/kg) and MgO (15.80 g/kg). Thus composting definitively constitutes the most optimal option to exploit these wastes.     

Alteration of male reproductive system in rats fed on red or white meat from tuna fish caught in the Gulf of Gab��s in Tunisian coast

Fish, a widely claimed healthy food for humans, could also pose problems to health due to (1) accumulation of pollutants, especially heavy metals, (2) presence of marine toxins such as tetrodotoxin, ciguatoxin or okadaic acid and (3) metabolic production of large amount of uric acid which may crystallize in kidney or in articulations. As tuna fish represents a large part of the traditional food in some countries, the possible impact of its consumption on public health was investigated, with special attention to biochemical and histological alterations related to the genital function. For that purpose, white or red muscle from tuna fish was added for 60 days to the diet of male rats, and attention was paid to biochemical and histological alterations related to the genital function. Feeding rats with white muscle, and much more markedly with red muscle known to be more metabolically active, resulted in (1) an elevated uric acid level in blood, (2) an increase in lead level in testis, (3) an atrophy of the genital tract, including testes, epididymis, prostate and seminal vesicles, (4) a lowering of plasma testosterone level, (5) a decrease in spermatozoids number and motility, (6) an oxidative stress in testes including an increase in lipids peroxidation level and enhanced superoxide-dismutase, catalase and glutathione-peroxidase activities. We conclude that consumption of tuna fish meat, especially the dark one, should be reduced.     

Isolation and characterization of facultative mixotrophic ammonia-oxidizing bacteria from constructed wetlands

Autotrophic ammonia-oxidizing bacteria (AOB) have been widely studied in constructed wetlands systems, while mixotrophic AOB have been less thoroughly examined. Heterotrophic bacteria were isolated from wastewater and rhizospheres of macrophytes of constructed wetlands, and then cultivated in a mixotrophic medium containing ammonium and acetic acid. A molecular characterization was accomplished using ITS-PCR amplification, and phylogenetic analysis based on 16S rRNA gene sequences. Results showed the presence of 35 bacteria, among 400 initially heterotrophic isolates, that were able to remove ammonia. These 35 isolates were classified into 10 genetically different groups based on ITS pattern. Then, a collection of 10 isolates were selected because of their relatively high ammonia removal efficiencies (ARE ≥ 80%) and their phylogenetic diversity. In conditions of mixotrophy, these strains were shown to be able to grow (increase of optical density OD₆₆₀ during incubation with assimilation of nitrogen into cellular biomass) and to oxidize ammonia (important ammonia oxidation efficiencies, AOE between 79% and 87%). Among these facultative mixotrophic AOB, four isolates were genetically related to Firmicutes (Bacillus and Exiguobacterium), three isolates were affiliated to Actinobacteria (Arthrobacter) and three other isolates were associated with Proteobacteria (Pseudomonas, Ochrobactrum and Bordetella).     

Simple analytical method for determination of pesticide residues in human serum by liquid chromatography tandem mass spectrometry

The aim of this study was to develop an analytical method for the determination of residues of organophosphorus and carbamate pesticides which are widely used in Tunisia. This method involves a liquid-liquid extraction procedure followed by liquid chromatography tandem mass spectrometry (LC/MS/MS) for the identification and quantification of compounds. Ionization of molecules was performed by the electrospray mode. Multiple reactions monitoring (MRM) was the acquisition mode used for the monitoring of two MS/MS transitions for each compound. The average recoveries obtained, at three different fortification levels, ranged between 65% and 106% for most of the pesticides studied, except for methamidophos (lower than 25%).The linearity of the method was in the range of 5 to 50 μ g/L with a correlation coefficient from 0.995 to 0.999, depending on the analyte. The estimated limit of detection and limit of quantification were 2 μ g/L and 5 μ g/L, respectively. The precision of the analytical procedure was satisfactory and the coefficients of variation, evaluated at three concentration levels were lower than 15% for most pesticides studied. The application of the method was investigated in a population of agricultural workers chronically exposed to various pesticides some of which, such as carbofuran, carbendazim, methomyl and pirimicarb, were detected in some serum samples.     

Impact of chlorpyrifos on cerebrum and cerebellum maturity in suckling rats

The purpose of our study is to assess the effect of chlorpyrifos (CPF) on rat cerebral and cerebellar maturity during the suckling period. Female Wistar rats were given 0.2?g?L^?1 of CPF in drinking water, equivalent to 40?mg?kg^?1 of body weight?day^?1, from day zero until day ten after delivery. In treated pups, plasma butyrylcholinesterase (BuChE) activity was inhibited by 70%. Cerebrum and cerebellum acetyl-cholinesterase (AchE) activities were reduced by 71 and 75%, respectively. The results suggest that CPF was distributed in pup tissues through the milk of lactating mothers, resulting in inhibition of AchE activities. At age 10 days, the CPF-treated pups showed a 28% decrease in body weight, a 23 and 41% decrease in plasma free T₃ and T₄ levels and reduction in cerebral and cerebellar protein content by 36 and 38%, respectively. Consistent histological changes were found in the cerebellum of CPF treated pups, with the external granular layer being markedly developed, the Purkinje cell bodies being poorly differentiated and abnormally distributed into the internal granular layer.     

Microbiological parameters and maturity degree during composting of Posidonia oceanica residues mixed with vegetable wastes in semi-arid pedo-climatic condition

The aim of this study was to characterize the biological stability and maturity degree of compost during a controlled pile-composting trial of mixed vegetable residues (VR) collected from markets of Tunis City with residues of Posidonia oceanica (PoR), collected from Tunis beaches. The accumulation in beaches (as well as their removal) constitutes a serious environmental problem in all Mediterranean countries particularly in Tunisia. Aerobic-thermophilic composting is the most reasonable way to profit highly-valuable content of organic matter in these wastes for agricultural purposes. The physical, chemical, and biological parameters were monitored during composting over 150 d. The most appropriate parameters were selected to establish the maturity degree. The main result of this research was the deduction of the following maturity criterion: (a) C/N ratio < 15; (b) NH4 +-N < 400 mg/kg; (c) CO2-C < 2000 mg CO2-C/kg; (d) dehydrogenase activity < 1 mg TPF/g dry matter; (e) germination index (GI) > 80%. These five parameters, considered jointly are indicative of a high maturity degree and thus of a high-quality organic amendment which employed in a rational way, may improve soil fertility and soil quality. The mature compost was relatively rich in N (13.0 g/kg), P (4.74 g/kg) and MgO (15.80 g/kg). Thus composting definitively constitutes the most optimal option to exploit these wastes.