Lamia Ayed

Culture conditions of tannase production by Lactobacillus plantarum

Lactobacillus plantarum produced an extracellular tannase after 24 h growth on minimal medium of amino acids containing 2 g tannic acid l−1. Enzyme production (6 U ml−1) was optimal at 37 °C and pH 6 with 2 g glucose l−1 and 7 g tannic acid l−1 in absence of O2.

Involvement of lignin peroxidase in the decolourization of black olive mill wastewaters by Geotrichum candidum.

Aim:  Decolourization of black olive mill wastewaters (OMW) by depolymerization of phenolic compounds by Geotrichum candidum.

Effect of nitrogen and carbon sources on Indigo and Congo red decolourization by Aspergillus alliaceus strain 121C.

The decolourizing ability of Aspergillus alliaceus 121C was investigated on solid medium. The effects of nitrogen (N), carbon (C) sources and supplements on the decolourization of Indigo and Congo red dyes were studied. It has been shown that both the nature and the quantity of available N- and C-sources exert an influence on growth and decolourization. For the six N-sources (NH(4)Cl, Diammonium Tartrate, urea, malt extract, peptone and yeast extract) tested for Congo red decolourization, 8mM yeast extract provided the higher decolourized zone diameter (80 mm) and colony diameter (80 mm). 12 mM urea provided the higher decolourized zone diameter (76+/-2mm) and colony diameter (80 mm) for Indigo decolourization. For the C-sources tested (glucose, starch, glycerol and lactose), above 12.5mM of glucose and 62.5mM of starch provided the higher decolourized zones diameters of 80 mm and 77+/-3mm for Indigo and Congo red, respectively. When the fungi was grown in liquid medium containing optimum carbon and nitrogen sources supplemented with oak sawdust and wheat bran, more than 98.6% and 98% of colour removal are obtained for Indigo and Congo red dyes, respectively. The detection of ligninolytic enzymes proved that laccase and lignine-peroxidase (LiP) are the two enzymes responsible of the decolourization of the two dyes.

Evaluation of the maturity of organic waste composts

Olive-mill wastes represent a significant environmental problem in Mediterranean areas due to their significant production during a short period of time. Their high polyphenol, lipid and organic acid concentrations make them phytotoxic wastes. Composting is one of the technologies used for the valorization of those wastes, producing a fertilizer useful for poor soils. The present study is an attempt to elaborate upon organic matter transformations and define the parameters for product maturity by adapting chemical and spectroscopic methods during composting. The aim of this work was to study the changes involved in the composting process of four piles during 200 days, and follow up the maturity of the final product during composting. Fourier transform infrared (FTIR) spectroscopy has been proven to be an appropriate analytical method for the qualitative assessment of compost stability. FTIR spectroscopy results revealed enrichment in aromatic structures and a degradation of the aliphatic and alcoholic structures indicating stabilization of the final compost. The results showed that stability of the final product was reached after 7 months of composting. The phytotoxic effects of olive mill wastes and animal manures was assessed by germination index. Indeed, the germination indices of piles 1, 2, 3 and 4 reached 131.31%, 72%, 90.56%, and 105.37%, respectively, at the end of the process. This demonstrated the absence of phytotoxicity in the majority of mature composts.

Exploring bioaugmentation strategies for the decolourization of textile wastewater using a two species consortium (Bacillus cereus and Bacillus pumilus) and characterization of produced metabolites

Abstract Two bacterial strains, Bacillus cereus and Bacillus pumilus, were isolated from the sludge of an aerobic reactor treating textile wastewater containing indigo dye. These strains were chosen as augmented decolourizers which were mixed in various ratios with the activated sludge and the effect of their concerted metabolism on the decolourization and the biodegradation efficiencies were studied. Results showed that there was an equilibrated ratio between the bioaugmented bacteria and the other microorganisms of the activated sludge. However, the best yields were observed for the combination 33% activated sludge, 33% Bacillus cereus and 33% Bacillus pumilus, with a colour and carbon oxygen demand (COD) removal of 98% and 99% respectively, obtained after 48 h of incubation. The high performance liquid chromatography (HPLC), Proton Nuclear Magnetic Resonance (1H NMR) analysis of the produced metabolites after the biodegradation of the dye by the bioaugmented consortium showed the presence of protons on...

Response surface methodology for optimization of the treatment of textile wastewater by a novel bacterial consortium: Enzymes and metabolites characterization

Textile wastewater (TWW) causes many environmental problems, and colored substances must be removed from it before their discharge into the environment. An optimization process was analyzed using custom response surface methodology (RSM). In the present study, the effect of different combinations of eight strains was studied using equilateral triangle diagram (Minitab 14.0) and mixture experimental design to assess color and chemical oxygen demand (COD) removal during the growth of species. Under optimal conditions, the bacterial consortium developed was able to decolorize completely (>84%) the dye within 72 h. The color and COD removal were 89.97 and 84.71%, respectively. A significant increase in azoreductase, lignin peroxidase and laccase activities in the cells were obtained after complete decolorization. Ultraviolet (UV)–vis and nuclear magnetic resonance (NMR) spectroscopy analysis confirmed the biodegradability of the TWW by the developed bacterial consortium.

Effect of Water Quality on Heavy Metal Redistribution-Mobility in Agricultural Polluted Soils in Semi-Arid Region

Abstract Mornag Plain is a coastal area of the Mediterranean basin, which has undergone an agricultural industrial boom. The aim of this study was to investigate the different water qualities used for irrigation on heavy metal mobility in these polluted agricultural soils. The geo-accumulation indices for heavy metals (Ni, Cr, Pb, Cd, Cu, and Zn) revealed that industrial activities and used treated wastewater (TWW) contributed to soil pollution, and water irrigation always decreased this contamination. After long-term use of different water types, high perturbation of heavy metal redistribution has occurred. Groundwater use altered all heavy metal redistributions in the irrigated soil among various soil-solid and soil-solution fractions, as compared to the unirrigated soil. Slight acid water use transferred some metals from different solid phase components into water-soluble and exchangeable fractions. However, TWW use transformed some Ni, Cr, Cd, Cu, and Zn from water-soluble and exchangeable fractions to less labile fractions, particularly into organically bound fractions. Reuse of conventional water within the same soil decreased the whole soil redistribution index values, indicating tendency to return to the pattern of distribution of groundwater-irrigated soil.

Water Quality and Toxic Element Effects on Isohumic Soil Properties and Crops in Semi-arid Regions

Treated wastewater (TWW) and freshwater used separately or within the same agricultural soil is a key element in soil parameter evolution, soil–plant pollution and crop yields. The long-term application of TWW increased CaCO3, P, N, K, TOC, metal contents, pH and salinity in isohumic soil in semi-arid and arid climates. Also, it was found that using freshwater after TWW within the same land leached soil compounds and pollutants. Consequently, a clear decline of salinity, pH, macronutrient and pollutant concentrations occured. Therefore, the economic profitability in topsoil decreased. TWW contributed to crop production increase, despite high fertilizer and metal concentrations in TWW and soil. Also, no toxic metal trace was detected in cultivated plants despite soil pollution. Occasional rainwater removed the stable part of fertilizers in topsoil and slightly improved plant development.

Pilot Plant Experiences Using Activated Sludge Treatment Steps for the Biodegradation of Textile Wastewater

Considering both the volume and the effluent composition, the textile industry wastewater is rated as the most polluting among all industrial sectors. Important pollutants are present in textile effluents; they are mainly recalcitrant organics, colour, toxicants and inhibitory compounds (Khelifi et al., 2008). Textile industries however, have caused serious environmental problems because of the wastewater produced. Most textile industries produce wastewater with relatively high BOD, COD, suspended solids and color. The wastewater may also contain heavy metals depending on the type of coloring substances used. In general, the objective of textile industry wastewater treatment to reduce the level of organic pollutants, heavy metal, suspended solids and color before discharge into the river. Coloring substances are used for dyeing and printing processes. The wastewater from these two processes is the most polluted liquid waste in a textile industry. Biological, chemical, physical or the combination of the three treatment technologies can be used to treat textile industry liquid waste (Suwardiyno and Wenten, 2005). It has been proven that some of these dyes and/or products are carcinogens and mutagens (Manu and Chaudhari 2003). A part from the aesthetic deterioration of the natural water bodies, dyes also cause harm to the flora and fauna in the natural environment (Kornaros and Lyberatos 2006). So, textile wastewater containing dyes must be treated before their discharge into the environment (Forgas et al., 2004). Numerous processes have been proposed for the treatment of coloured waste water e.g., precipitation, flocculation, coagulation, adsorption and wet oxidation (Hongman et al., 2004; Thomas et al., 2006). All these methods have different colour removal capabilities, capital costs and operating speed. Among these methods coagulation and adsorption are the commonly used; however, they create huge amounts of sludge which become a pollutant on its own creating disposal problems (Nyanhongo et al., 2002). Among low cost, viable alternatives, available for effluent treatment and decolourization, the biological systems are recognised, by their capacity to reduce biochemical oxygen demand (BOD) and chemical oxygen demand (COD) by conventional aerobic biodegradation (Forgas et al., 2004; Kornaros and Lyberatos 2006; Balan and