High-performance biological treatment of tuna wash processing wastewater using Yarrowia lipolytica.

It is well known that the lack of an effective treatment of tuna wash processing wastewater may pose substantial environmental and public health hazards. The present work investigates the performance of biological treatment of tuna wash processing wastewater (TWPW) by using Yarrowia lipolytica. Under optimized experimental conditions (pH "6.40-6.50" and 29 °C), Y. lipolytica reduced the pollution level of the crude and the diluted TWPW after only 7 days of incubation. The Yarrowia treatment leaded to a reduction of 66% chemical oxygen demand, 69.8% total organic carbon, 66% salinity, and phosphorus total (100%) removal of the crude TWPW, while the treated-diluted TWPW revealed significant reductions in chemical oxygen demand and total organic carbon (75% and 74%, respectively), as well as salinity (68%). Interestingly, a total removal of nitrogen and phosphorus from the diluted TWPW was obtained. Under high salinity, an important Y. lipolytica biomass of 5 g L-1 is produced with high levels of lipids and protein contents at around 336 ± 12.2 mg g-1 and 302.15 ± 5.44 mg g-1, respectively. The phytotoxicity assessment of the treated TWPW on fenugreek seeds shows promising results, which reveals the good performance of Yarrowia treatment in reducing the toxicity of this wastewater.

Pb doped ZnO nanoparticles for the sorption of Reactive Black 5 textile azo dye.

In this study, Pb doped ZnO nanoparticles were synthesized by a sol-gel technique for the sorption of Reactive Black 5 (RB5) textile dye in aqueous solution. The ZnO:Pb (2 and 4%) nanoparticles have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and cryogenic nitrogen adsorption method. The average size of the synthesized nanoparticles was less than 100 nm and the surface areas were 18.8 and 20.8 m2/g, respectively for ZnO:Pb 2% and ZnO:Pb 4%. Batch sorption experiments were performed for color removal of RB5 dye at ambient temperature and 30 mg/L dye concentration. The central composite design with response surface methodology was used to study the effect of sorption condition (pH, nanoparticles dose and contact time). The significance of independent variables and their interactions was tested by analysis of variance. The optimum conditions of color removal were pH = 7, 2 g/L dose of nanoparticles and a contact time of 79 min. The color removal performance was 79.4 and 98.1% for ZnO:Pb 2 and 4% respectively. The pseudo-second-order model described well the removal rates while the Langmuir model fitted well the adsorption isotherms.

A new practical approach for the biological treatment of a mixture of cheese whey and white wastewaters using Kefir grains.

Kefir grains are a microbial consortium of different genera of bacteria and yeasts. In this study, the performance of Tunisian Kefir grains during the biological treatment of a mixture of Gouda cheese whey and white wastewaters (GCW) in ratio 1:1 with very high organic matter concentration is investigated. The biological process was evaluated and optimized through the response surface methodology. Under the optimum conditions, Kefir grains concentration of 1.02%, temperature at 36.68 °C, and incubation time of 5.14 days, the removal efficiencies of COD, PO43-, and NO3- were 87, 37.48, and 39.5%, respectively. Interestingly, the reusability tests of the grains proved not only their high resistance to harsh environmental conditions but also their great potential for more practical applications. Particularly, different strains were isolated from the grains and identified as Kluyveromyces marxianus, Lactoccocus lactis, Lactobacillus kefiri, and Bacillus spp. using 16S rDNA sequence analysis and rep-PCR fingerprinting. At the biological level, the raw GCW (RGCW) has a negative impact on the Hordeum vulgare both on seed germination, and on the growth parameters of seedlings. Interestingly, after Kefir grains treatment, the treated GCW (TGCW) allow a seedlings growth and germination rate similar to those soaked in water.

Mixed culture of Lactococcus lactis and Kluyveromyces marxianus isolated from kefir grains for pollutants load removal from Jebel Chakir leachate.

The wastewater from the dumping site usually contains high pollutant levels. Biological process and physico-chemical treatments are among several technologies for wastewater treatment. Using microorganisms in the treatment of landfill leachate is an emerging research issue. Furthermore, bioremediation is a feasible approach for pollutants removal from landfill leachate which would provide an efficient way to resolve the issue of landfill leachate. In this study, the performance of yeast and bacteria isolated from kefir grains was assessed for landfill leachate treatment. Kefir grains microbial composition was evaluated by molecular approaches (Rep-PCR and 16S rRNA gene sequencing). The obtained outcomes denoted that high concentrations of lactic acid bacteria and yeast populations (over 107  CFU/ml) were found in the kefir grains and were essentially composed of Lactococcus lactis, Lactobaccillus kefirien, bacillus sp., L. lactis, and Kluyveromyces marxianus. The co-culture with 1% of inoculum size was demonstrated as the most efficient in the degradation of different contaminants. The overall abatement rate of chemical oxygen demand (COD), ammonium nitrogen ( NH 4 + - N ), and salinity were 75.8%, 85.9%, and 75.13%, respectively. The bioremediation process resulted in up of 75% removal efficiency of Ni and Cd, and a 73.45%, 68.53%, and a 58.17% removal rates of Cu, Pb, and Fe, respectively. The research findings indicate the performance of L. lactis and K. marxianus co-culture isolated from kefir grains for the bioremediation of LFL. PRACTITIONER POINTS: Isolation and identification of microorganisms from kefir grains was carried out. Biological treatment of LFL using monoculture of (Lactoccocus lactis; Kluyveromyces marxianus) and co-culture (5% of L. lactis and 5% K. marxianus) has been performed. Biological treatment using co-culture strain is an effective approach to remove organic matter, NH 4 + - N and heavy metals.

Aloe sp. leaf gel and water glass for municipal wastewater sludge treatment and odour removal.

Aloe gel (Alg), which is a natural extract from the Aloe sp. plant, was evaluated in this study for its potential use as a bioflocculant to treat urban wastewater sewage sludge. The gel was used alone and combined with water glass (WG) under controlled conditions in laboratory experiments. Alg was found effective to settle the flocculated sludge rapidly and remove distinctive unpleasant odours of the sludge as highlighted by gas chromatography-mass spectrometry (GC/MS) analysis. Furthermore, Alg was pH tolerant and had no effect in changing the pH of the wastewater. The optimum dose of Alg was 3% at which a sludge volume index (SVI) of 45.4 mL/g was obtained within 30 min settling time. To enhance the treatment performances of Alg, WG was also evaluated as an alkali agent to further reduce the chemical oxygen demand (COD) and ammonia (NH4-N) in the wastewater. At equal doses of 3% of WG and Alg each, the combined treatment outcomes showed high turbidity and NH4-N removals of 83 and 89%, respectively, but the overall COD removal was at best 25%. The settling rate of treated sludge with combined Alg/WG was very rapid giving an SVI of 25.4 mL/g within only 5 min.

A new insight into highly contaminated landfill leachate treatment using Kefir grains pre-treatment combined with Ag-doped TiO2 photocatalytic process.

This study investigates the performance of the combination of biological pre-treatment with Kefir grains (KGs) and photocatalytic process using Ag-doped TiO2 nanoparticles (NPs) for the simultaneous removal of toxic pollutants from landfill leachate (LFL). After 5 days of 1% (w/v) KGs pre-treatment at 37 °C, TOC, COD, NH4+-N, and PO43- removal rates were 93, 83.33, 70 and 88.25%, respectively. The removal efficiencies were found to be 100, 94, 62.5, 53.16 and 47.52 % for Cd, Ni, Zn, Mn and Cu, respectively. The optimal conditions of Ag-doped TiO2 photocatalytic process were optimized using Box-Behnken design and response surface methodology (BBD-RSM) to enhance the quality of pre-treated LFL. Interestingly, Ag-doped TiO2 photocatalytic process increases the overall removal efficiencies to 98, 96, 85 and 93% of TOC, COD, NH4+-N, and PO43-, respectively. Furthermore, the removal efficiency of toxic heavy metals was gradually improved. In addition, KGs and Ag-doped TiO2 exhibited excellent recyclability showing the potential of combined biological/photocatalytic process to treat hazardous LFL.

Effect of liquid depth on microcontaminant removal by solar photo-Fenton with Fe(III):EDDS at neutral pH in high salinity wastewater.

In arid Mediterranean countries, such as Tunisia, wastewater often has high salinity, being an obstacle to the elimination of microcontaminants for the reuse of water in agriculture. In this paper, the photo-Fenton process in raceway pond reactors (RPRs) has been successfully applied to a simulated secondary effluent from a Tunisian urban wastewater treatment plant (WWTP), with high chloride load. A mixture of three contaminants of emerging concern (CECs) was used as model pollutants at 50 µg/L each (one antibiotic, sulfamethoxazole and two pesticides, pyrimicarb and imidacloprid). All the assays were conducted at neutral pH with 0.1 mM Fe(III):EDDS at 1:1 molar ratio. The effect of hydrogen peroxide initial concentration (20, 30, and 90 mg/L) on microcontaminant removal was studied. Different liquid depths (5 and 15 cm) were selected to assess the relationship between the microcontaminant removal and the volumetric rate of photon absorption (VRPA). Although the reaction rate was initially photo-limited, after a short reaction time of 15 min, the final yield (≈ 80% of CEC removal) was limited by the photo-degradation of the Fe(III):EDDS complex and excess H2O2 was found at all concentrations used. Therefore, treatment times below 15 min should be used. The treatment capacity was three times higher when the liquid depth was increased from 5 to 15 cm. For the first time, these results show that the operation of a 15 cm-deep RPR in continuous flow mode would be suitable for large-scale implementation of the solar photo-Fenton process.

Valorization of residual soft drinks by baker's yeast production and insight for dairy wastewater whey incorporation.

Residuals are responsible for the polluting load increase of soft drink industry wastewater due to their high sugar contents. The present work proposes an upstream segregation of residuals to be biologically treated by the bioconversion of their carbohydrates content into baker's yeast biomass. Carbonated soft drinks (CSD) and nectars and juices (NJ) ranges were considered. Different incorporation ratios of NJ in the CSD (0-75%) have been investigated for balanced growth medium. Despite the nitrogen deficiency of media, results showed that NJ incorporation promoted the microbial growth. Media containing more than 50% of NJ exhibited ∼25% sugar-biomass conversion rates. The chemical oxygen demand (COD) of the media exceeded 70% at the end of fermentation. Moreover, valuable components were recovered by yeast production. Nutrient consumption rates varied from 65.4% for sugar and calcium content to in excess of 99% for protein and other minerals. In order to investigate an available and low-cost source of nitrogen for yeast production, partial substitution of the soft drink growth medium by bactofugate whey was evaluated. The soft drink-whey mixture medium fermentation resulted in 63% COD removal rate after 28 h. Meanwhile, the biomass production yield revealed an improvement of about 25% compared to the balanced soft drink medium (NJ50).

Novel approach for the use of dairy industry wastes for bacterial growth media production.

This work proposes a novel approach for the reuse and the recovery of dairy wastes valuable components. Thermal coagulation was performed for dairy effluents and the main responsible fraction for the organic matter content (protein and fat) was separated. Dairy curds were prepared for the formulation of bacterial growth media. Protein, sugar, fat and fatty acids contents have been assessed. Samples treated at 100 °C exhibited marked improvement in terms of protein (25-50%) recovery compared to those treated at 80 °C. Fatty acid analysis revealed the presence of unsaturated fatty acids (mainly oleic acid) that are essential to promote Lactobacillus growth. Previously isolated and identified bacterial strains from dairy wastes (Lactobacillus paracasei, Lactobacillus plantarum, Lactococcus lactis and Lactobacillus brevis) were investigated for their ability to grow on the formulated media. All the tested lactic acid bacteria exhibited greater bacterial growth on the formulated media supplemented with glucose only or with both glucose and yeast extract compared to the control media. By reference to the commercial growth medium, the productivity ratio of the supplemented bactofugate (B) and decreaming (D) formulated media exceeded 0.6 for L. paracasei culture. Whereas, the productivity ratio of the supplemented B medium was greater than 1 compared to the control medium for all the tested strains. As for the supplemented D medium, its productivity ratio was greater than 1 compared to the control medium for both L. paracasei and L. plantarum strains.

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.

Processed milk waste recycling via thermal pretreatment and lactic acid bacteria fermentation.

Processed milk waste (MW) presents a serious problem within the dairy industries due to its high polluting load. Its chemical oxygen demand (COD) can reach values as high as 80,000 mg O2 L-1. This study proposes to reduce the organic load of those wastes using thermal coagulation and recover residual valuable components via fermentation. Thermal process results showed that the COD removal rates exceeded 40% when samples were treated at temperature above 60 °C to reach 72% at 100 °C. Clarified supernatants resulting from thermal treatment of the samples at the temperatures of 60 (MW60), 80 (MW80), and 100 °C (MW100) were fermented using lactic acid bacteria strains without pH control. Lactic strains recorded important final cell yields (5-7 g L-1). Growth mediums prepared using the thermally treated MW produced 73% of the bacterial biomass recorded with a conventional culture medium. At the end of fermentation, mediums were found exhausted from several valuable components. Industrial scale implementation of the proposed process for the recycling of industrial MWs is described and discussed.

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 cheese's 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.