Ismail Trabelsi

Eco-friendly process combining physical–chemical and biological technics for the fermented dairy products waste pretreatment and reuse

Residual fermented dairy products resulting from process defects or from expired shelf life products are considered as waste. Thus, dairies wastewater treatment plants (WWTP) suffer high input effluents polluting load. In this study, fermented residuals separation from the plant wastewater is proposed. In the aim to meet the municipal WWTP input limits, a pretreatment combining physical-chemical and biological processes was investigated to reduce residual fermented dairy products polluting effect. Yoghurt (Y) and fermented milk products (RL) were considered. Raw samples chemical oxygen demand (COD) values were assessed at 152 and 246 g.L-1 for Y and RL products, respectively. Following the thermal coagulation, maximum removal rates were recorded at 80 °C. Resulting whey stabilization contributed to the removal rates enhance to reach 72% and 87% for Y and RL samples; respectively. Residual whey sugar content was fermented using Candida strains. Bacterial growth and strains degrading potential were discussed. C. krusei strain achieved the most important removal rates of 78% and 85% with Y and RL medium, respectively. Global COD removal rates exceeded 93%.

Genetic Characterization of Lactic Acid Bacteria Isolated from Tunisian Milk Waste and their Antimicrobial Activity Against some Bacteria Implicated in Nosocomial Infections.

BACKGROUND A total of 94 lactic acid bacteria (LAB) were isolated from Tunisian artisanal (Ricotta cheeses whey) and industrial (bactofugate) milk waste, identified and then screened for their antimicrobial activity against some bacteria implicated on nosocomial infections. OBJECTIVE Bacterial genera and species identification was performed using molecular tools. The antimicrobial activity was tested against 7 strains of Gram-negative bacteria and 4 strains of Gram-positive bacteria as well as 6 yeasts. METHOD The Crude extract was found to have a narrow antimicrobial spectrum on Gram-positive bacteria mainly Listeria monocytogenes. Among the strains which showed antibacterial activity, four were determined to be bacteriocins-producers. They were identified as Lactococcus lactis. RESULTS Brain Heart Infusion (BHI) Agar was found more adapted than Man, Rogosa and Sharpe (MRS) to investigate the antimicrobial activity of L. actococcus lactis against L. isteria monocytogenes. The genetic determinants encoding the antimicrobial peptides were targeted by specific PCR. CONCLUSION All L. lactis bacteriocin producing strains possessed the Nisine Z gene (nisZ) except for one, which contained both Nisine A and Nisine Z genes (nisA and nisZ). They have been identified as antilisterial agentS.

Pyrolysis of Date palm waste in a fixed-bed reactor: Characterization of pyrolytic products

The pyrolysis of several Tunisian Date Palm Wastes (DPW): Date Palm Rachis (DPR), Date Palm Leaflets (DPL), Empty Fruit Bunches (EFB) and Date Palm Glaich (DPG) was run using a fixed-bed reactor, from room temperature to 500°C, with 15°C/min as heating rate and -5°C as condensation temperature, in order to produce bio-oil, biochar and syngas. In these conditions, the bio-oil yield ranges from 17.03wt% for DPL to 25.99wt% for EFB. For the biochar, the highest yield (36.66wt%) was obtained for DPL and the lowest one (31.66wt%) was obtained from DPG while the syngas production varies from 39.10wt% for DPR to 46.31wt% DPL. The raw material and pyrolysis products have been characterized using elemental analysis thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM). The syngas composition has been characterized using gas analyzer.

Pyrolysis of Tunisian Date Palm Residues for the Production and Characterization of Bio-Oil, Bio-Char and Syngas

Lignocellulosic biomass has been projected as an abundant carbon-neutral renewable source, which can decrease CO2 emissions and atmospheric pollution. Thus, it is a promising alternative to limit crude oil, which can be utilized to produce bio fuels, biomolecules and biomaterials (Barakat et al. in Bioresour Technol 134: 362–373, 2013). In Tunisia, one of the most available lignocellulosic biomass is “Date Palm residues” which are produced yearly (around 200,000 tons per year; CRDA-Kebili 2011) since the economy is based on agricultural activities and mainly dates production. These by-products of Date palm tree extraction activities management could generate many environmental problems (landfilling, combustion …etc.).

Organic Compounds and Heavy Metals Simultaneous Removal from a Tunisian Landfill Leachate Using Dairy Rejects

Landfilling is one of the most widely used processes for the disposal of municipal solid waste (MSW). It is designed to dispose high quantities of waste at economical costs. Landfill management may pose serious environmental impacts through the discharge of highly polluted wastewater also known as leachate. The treatment of landfill leachates (LFL) is very complicated, expensive and requires various combined process applications due to their high COD and nitrogen levels.