Optimized decolorization of two poly azo dyes Sirius Red and Sirius Blue using laccase-mediator system.

Factors, namely pH, laccase-like activity, dyes concentration as well as 1-Hydroxybenzotriazole (HBT) concentration was examined. The results indicated that the maximum decolorization yield and rate reached 98.30 ± 0.10% and 5.84 ± 0.01%/min, respectively for Sirius Blue, and 99.34 ± 0.47% and 5.85 ± 0.12%/min, respectively for Sirius Red after 4 h. The presence of the redox mediator 1-hydroxybenzotriazole (HBT) greatly improved the decolorization levels. The optimum concentrations of HBT, dyes, and laccase were 0.62 mM, 50 mg/L, and 0.89 U/mL respectively at pH 4.58 for both dyes. Phytotoxicity tests using treated and untreated dyes proved that the applied treatment slightly decreased the toxicity of the by-products. However, the germination index (GI) increased from 14.6 to 36.08% and from 31.6 to 36.96% for Sirius Red and Sirius Blue, respectively. The present study focused on the treatment of two recalcitrant azo dyes, namely: Sirius Blue (Direct Blue 71) and Sirius Red (Direct Red 80). The decolorization was performed using cell-free supernatant from Coriolopsis gallica culture with high laccase activity. Response surface methodology (RSM) and Box-Behnken design were applied to optimize the decolorization of the two tested dyes. The effect of four.

Effect of non-uniform heat rise/fall and porosity on MHD Williamson hybrid nanofluid flow over incessantly moving thin needle.

In this work, a novel enhanced model of the thermophysical characteristics of hybrid nanofluid is introduced. An innovative kind of fluid called hybrid nanofluid has been engineered to increase the heat transfer rate of heat and performance of thermal system. A growing trend in scientific and industrial applications pushed researchers to establish mathematical models for non-Newtonian fluids. A parametric study on theheat transfer and fluid flow of a Williamson hybrid nanofluid based on AA7075-AA7072/Methanol overincessantly moving thin needle under the porosity, Lorentz force, and non-uniform heat rise/fallis performed. Due to similarity variables, the partial differential equations governing the studied configuration undergo appropriate transformation to be converted into ordinary differential equations. The rigorous built-in numerical solver in bvp4c MATLAB has been employed to determine the numerical solutions of the established non-linear ordinary differential equations. It is worthy to note that velocity declines for both AA7075/Methanol nanofluid and AA7075- AA7072/Methanol hybrid nanofluid, but highervelocitymagnitudes occur for theAA7075/Methanol whilethe Williamson fluid parameters increased. It is alsoconcluded that as the porosity parameter isincreased, the flow intensity decreases gradually. It is worthy to note that for both non-uniform heat-rise and fall parameters, the temperature of the fluid gets stronger. Mounting valuesof needle thickness parameter leads to reduction in fluid speed and temperature. It is noticedthat as volume fractions of both types of nanoparticles are augmented then fluidvelocity and temperature amplify rapidly. A Comparison of current and published results is performed to ensure the validity of the established numerical model.

Efficient Decolorization of the Poly-Azo Dye Sirius Grey by Coriolopsis gallica Laccase-Mediator System: Process Optimization and Toxicity Assessment.

The textile industry produces high volumes of colored effluents that require multiple treatments to remove non-adsorbed dyes, which could be recalcitrant due to their complex chemical structure. Most of the studies have dealt with the biodegradation of mono or diazo dyes but rarely with poly-azo dyes. Therefore, the aim of this paper was to study the biodegradation of a four azo-bond dye (Sirius grey) and to optimize its decolorization conditions. Laccase-containing cell-free supernatant from the culture of a newly isolated fungal strain, Coriolopsis gallica strain BS9 was used in the presence of 1-hydroxybenzotriazol (HBT) to optimize the dye decolorization conditions. A Box-Benken design with four factors, namely pH, enzyme concentration, HBT concentration, and dye concentration, was performed to determine optimal conditions for the decolorization of Sirius grey. The optimal conditions were pH 5, 1 U/mL of laccase, 1 mM of HBT, and 50 mg/L of initial dye concentration, ensuring a decolorization yield and rate of 87.56% and 2.95%/min, respectively. The decolorized dye solution showed a decrease in its phytotoxicity (Germination index GI = 80%) compared to the non-treated solution (GI = 29%). This study suggests that the laccase-mediator system could be a promising alternative for dye removal from textile wastewater.

Removal of Organic Matter from Tunisian Industrial Phosphoric Acid by Adsorption onto Purified Natural Illite/Kaolinite Clay: Kinetics, Isothermal and Thermodynamic Studies.

This work aims to use a green, economical and efficient adsorbent to remove organic matter from Tunisian industrial wet phosphoric acid (WPA: 52% P2O5). For this purpose, a natural and abundant clay is extracted from the Douiret, Tataouine deposit in southern Tunisia. This clay is being tested for the first time as an adsorbent in WPA medium. The raw clay and purified clay are analysed using standard analytical techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, and BET methods. The results show that the raw clay is a mixture of illite and kaolinite, with other mineral impurities, mainly quartz. Organic matter adsorption tests show that the purified clay exhibits greater effectiveness than raw clay. The parametric study with purified clay indicates that temperature, contact time, and clay dosage strongly influence organic matter adsorption. The highest adsorption occurs at 60 °C after 50 min, reaching 56% with 8 g of purified clay per kg of WPA. Among several recognised models, the pseudo-second-order kinetic model and the Sips isotherm model are the most suitable for modelling the experimental data. This study suggests that Douiret clay can be considered an effective, inexpensive and environmentally friendly adsorbent for eliminating organic matter in industrial phosphoric acid.

The Phytochemical and Pharmacological Properties of Citrus sinensis 'Maltese Half-blood' Essential Oil Peels Extracted and Optimized by Response-surface Methodology.

BACKGROUND: Citrus fruits have been a valuable economic crop for thousands of years. Furthermore, citrus essential oils are significant in the perfume, food, and beverage sectors, as well as aromatherapy and medical medicines. AIMS: The present study aims to evaluate the phytochemical and pharmacological potentials of the optimized Citrus sinensis 'Maltese half-blood' essential oils peels (CsEO) extraction yields using Response-Surface Methodology (RSM). OBJECTIVE: There have been few investigations on Citrus sinensis 'Maltese half-blood' essential oil. METHODS: Citrus sinensis 'Maltese half-blood' essential oil peels (CsEO) extraction yields were performed by hydro-distillation and optimized by using Response-Surface Methodology (RSM). The oils were analysed by GC-MS. Different chemical tests were used to evaluate antioxidant activities. The healing potential was evaluated using models' wounds on Wistar rats. RESULTS: The RSM optimization demonstrated the highest yield of CsEO of 6.89 g/100 g d.b. All three tested factors significantly influenced the CsEO extraction yield: washing saline solution concentration, washings number, and drying percentage of peels. Significant antioxidant activities were noted in CsEO: the DPPH assay reported an IC50 of 0.225 ± 0.014 mL/mg, the FRAP assay showed an IC50 of 0.235 ± 0.001, and the NO assay was an IC50 in order of 0.259 ± 0.019. CsEO was not genotoxic and considerably decreased the levels of DNA lesions induced by oxidants. Also, applying a cream with CsEO on wounds promotes significantly rapid wound healing. CONCLUSION: CsEO could be considered a rich natural source of antioxidants and bio-compounds to accelerate wound healing. It can be used in pharmaceutical sectors as an alternative to synthetic chemicals.

Optimization using response surface methodology of phospholipase C production from Bacillus cereus suitable for soybean oil degumming.

This work deals with the optimization of an extracellular phospholipase C production by Bacillus cereus (PLCBc) using Response Surface Methodology (RMS) and Box-Behnken design. In fact, after optimization, a maximum phospholipase activity (51 U/ml) was obtained after 6 h of cultivation on tryptone (10 g/L), yeast extract (10 g/L), NaCl (8.125 g/L), pH 7.5 with initial OD (0.15). The PLCBc activity, esteemed by the model (51 U) was very approximate to activity gutted experimentally (50 U). The PLCBc can be considered as thermoactive phospholipase since it showed a maximal activity of 50 U/mL at 60 °C using egg yolk or egg phosphatidylcholine (PC) as substrate. In addition, the enzyme was active at pH 7 and is stable after incubation at 55 °C for 30 min. The application of B. cereus phospholipase C in soybean oil degumming was investigated. Our results showed that when using enzymatic degumming, the residual phosphorus decrease more than with water degumming, indeed, it passes from 718 ppm in soybean crude oil to 100 ppm and 52 ppm by degumming using water and enzymatic process, respectively. The diacylgycerol (DAG) yield showed an increase of 1.2% with enzymatic degumming compared to soybean crude oil. This makes our enzyme a potential candidate for food industrial applications such as enzymatic degumming of vegetable oils.

The response surface methodology for optimization of Halomonas sp. C2SS100 lipase immobilization onto CaCO3 for treatment of tuna wash processing wastewater.

An immobilized enzyme could exhibit selectively modified physicochemical properties, and it might offer a better environment for the enzyme activity. In this study, the immobilization yield of crude Halomonas sp. lipase was optimized to improve its stability. Thanks to its high adsorption capacity, CaCO3 has been chosen as support for the immobilization process. Furthermore, response surface methodology (RSM) was used to determine optimal conditions for the immobilization of the bacterial lipase. Five tested factors (enzyme solution, support amount, time, temperature, and acetone volume) were optimized applying a central composite design of RSM. The maximum yield of lipase immobilization was improved to 96%. Furthermore, a biochemical characterization proved a significant improvement of the immobilized lipase stability. The immobilized enzyme is more stable at extreme pH values and high temperatures than the free one. We also tested the reusability of the immobilized lipase by evaluating the recovery of the support using simple filtration. Thanks to its high stability, the immobilized lipase was invested in an effective treatment of tuna wash processing wastewater. The oil biodegradation efficiency was established at 81.5% and was confirmed by Fourier transformation infrared spectrometry. Likewise, the biological oxygen demand values were reduced which makes a possible reduction of the wastewater pollution degree.

Optimization of a novel, gluten-free bread's formulation based on chickpea, carob and rice flours using response surface design.

This study aimed to develop nutritious, gluten-free bread with high quality characteristics using a mixture of chickpea, carob and rice flours as substitutes of wheat flour. To optimize the bread formulation, a Box-Behnken experimental design was conducted to evaluate the effect of the corresponding flour blend addition, proofing time and water amount addition on the physicochemical, technological and sensory properties of the obtained formulated bread. The optimized formulation was calculated to contain 70% of mixture flour and 100% of water, with a proofing time of 40 minutes. This formulation produced bread with greater specific volume ( 3.73 ± 0.37 cm3/g) and less baking loss ( 22.98 ± 0.94 % ) than those of control (+) bread ( 2.93 ± 0.21 cm3/g and 31.65 ± 0.72 % , respectively). Findings proved that the mixture flour based on chickpeas, carob and rice represents a good alternative to make gluten-free bread with acceptable baking properties.

Optimization of reactive black 5 decolorization by the newly isolated Saccharomyces cerevisiae X19G2 using response-surface methodology.

In the current investigation, the capacity of different yeast strains to decolorize reactive black 5 (RB-5) was assessed. A comparative study between the different strains demonstrated that Saccharomyces cerevisiae X19G2 exhibited the highest decolorization rate (69.20 ± 1.16%) after 48 h of incubation. This strain was selected to optimize the medium components' concentrations for maximum RB-5 decolorization. Response-surface methodology (RSM) was tested for the most significant parameters (glucose, yeast extract and RB-5 dye concentrations) that were previously determined by Plackett-Burman design. A dye decolorization rate of 99.59 ± 0.24% was achieved within 48 h using a maximum RB-5 concentration (0.15 g/L) with glucose and yeast extract concentrations equalling to 10.5 g/L and 1 g/L, respectively. Experimental data results proved to fit well with the pseudo-second order kinetics model. The phytotoxicity assessment was carried out using Raphanus sativus seeds to determine the toxicity of RB-5 before and after treatment by S. cerevisiae. Results suggested that germination rate and the length of seeds radical irrigated with 0.15 g/L of RB-5 decreased by 30 and 53%, compared to those irrigated with treated solution. Therefore, metabolites derived from decolorization of RB-5 by S. cerevisiae X19G2 were significantly less toxic than the original dye.

Optimization of the Decolorization of the Reactive Black 5 by a Laccase-like Active Cell-Free Supernatant from Coriolopsis gallica.

The textile industry generates huge volumes of colored wastewater that require multiple treatments to remove persistent toxic and carcinogenic dyes. Here we studied the decolorization of a recalcitrant azo dye, Reactive Black 5, using laccase-like active cell-free supernatant from Coriolopsis gallica. Decolorization was optimized in a 1 mL reaction mixture using the response surface methodology (RSM) to test the influence of five variables, i.e., laccase-like activity, dye concentration, redox mediator (HBT) concentration, pH, and temperature, on dye decolorization. Statistical tests were used to determine regression coefficients and the quality of the models used, as well as significant factors and/or factor interactions. Maximum decolorization was achieved at 120 min (82 ± 0.6%) with the optimized protocol, i.e., laccase-like activity at 0.5 U mL−1, dye at 25 mg L−1, HBT at 4.5 mM, pH at 4.2 and temperature at 55 °C. The model proved significant (ANOVA test with p < 0.001): coefficient of determination (R²) was 89.78%, adjusted coefficient of determination (R²A) was 87.85%, and root mean square error (RMSE) was 10.48%. The reaction conditions yielding maximum decolorization were tested in a larger volume of 500 mL reaction mixture. Under these conditions, the decolorization rate reached 77.6 ± 0.4%, which was in good agreement with the value found on the 1 mL scale. RB5 decolorization was further evaluated using the UV-visible spectra of the treated and untreated dyes.

Optimization of an organic solvent-tolerant lipase production by Staphylococcus capitis SH6. Immobilization for biodiesel production and biodegradation of waste greases.

Using the statistical approach, this work seeks to optimize the process parameters to boost the generation of an organic solvent-tolerant lipase by Staphylococcus capitis SH6. The main parameters influencing the enzyme production were identified by using Plackett-Burman's screening design. Among the test variables, only tryptone (25 g/L), malt extract (2.5 g/L), NaCl (10 g/L) and pH (7.0) contributed positively to enzyme production. Then, the crude lipase was immobilized by adsorption on CaCO3 at pH 10. A maximum immobilization efficiency of 82% was obtained by incubating 280 mg of enzyme with CaCO3 (1 g) during 30 min. The immobilized lipase was more stable toward organic solvents than the free enzyme. It retained about 90% of its original activity in the presence of ethanol and methanol. After that, the immobilized enzyme was used for biodiesel production by transesterification process between waste oil and methanol or ethanol during 24 h at 30 °C. Our results show that the lipase can be utilized efficiently in biodiesel industry. Likewise, we have demonstrated that the immobilized enzyme may be implicated in the biodegradability of waste grease; the maximum conversion yield into fatty acids obtained after 12 h at 30 °C, was 57%.

Extracellular neutral protease from Arthrospira platensis: Production, optimization and partial characterization.

Proteases are industrially important catalysts. They belong to a complex family of enzymes that perform highly focused proteolysis functions. Given their potential use, there has been renewed interest in the discovery of proteases with novel properties and a constant thrust to optimize the enzyme production. In the present study, a novel extracellular neutral protease produced from Arthrospira platensis was detected and characterized. Its proteolytic activity was strongly activated by ß-mercaptoethanol, 5,5-dithio-bis-(2-nitrobenzoic acid) and highly inhibited by Hg2+ and Zn2+ metal ions which support the fact that the studied protease belongs to the cysteine protease family. Using statistical modelling methodology, the logistic model has been selected to predict A. platensis growth-kinetic values. The optimal culture conditions for neutral protease production were found using Box-Behnken Design. The maximum experimental protease activities (159.79 U/mL) was achieved after 13 days of culture in an optimized Zarrouk medium containing 0.625 g/L NaCl, 0.625 g/L K2HPO4 and set on 9.5 initial pH. The extracellular protease of A. platensis can easily be used in the food industry for its important activity at neutral pH and its low production cost since it is a valuation of the residual culture medium after biomass recovery.

Optimization of gluten-free sponge cake fortified with whey protein concentrate using mixture design methodology.

This study aimed to optimize mixtures of whey protein concentrate (WPC) and two flours of rice and maize flours for the production of gluten-free sponge cakes. This was obtained by using mixture design methodology. WPC incorporation had positive effects on specific volume and baking loss of cakes, whilst, their incorporation increased their hardness. Considering all cakes properties, two formulas F1 (78.5% Maize, 15% Rice and 6.5% WPC) and F2 (82.4% Maize, 12% Rice and 5.6% WPC) were optimized using a mixture design. The microstructure F1 was more organized and very well structured with smaller aggregates. According to the organoleptic evaluation, F1 was also most appreciated by the tasting panel. The findings of the present study indicated that maize and rice flours, and WPC could be used as a substitute for wheat flour in producing sponge cakes of high quality.

Response-surface methodology for the production and the purification of a new H2 O2 -tolerant alkaline protease from Bacillus invictae AH1 strain.

This work deals with the optimization of the culture conditions of Bacillus invictae AH1 in order to increase the production level of the proteolytic activity. Response-surface methodology (RSM) was applied for the most significant fermentation parameters (concentration of wheat bran and K2 HPO4 /KH2 PO4 ) that were earlier identified by Plackett-Burman Design from seven possible factors. A central composite design was used and the quadratic regression model of producing active protease was built. A maximum protease activity was reached and validated experimentally, using a maximum wheat bran concentration (50 g/L) with increased K2 HPO4 /KH2 PO4 concentration (2.275 g/L). Protease production obtained experimentally coincident with the predicted value and the model was proven to be adequate. Interestingly, the use of RSM increased the protease production by four times (7,000 U/mL) using a low-cost substrate and a culture time of 40 hr, as compared to the standard culture conditions. In the second part of this study, a H2 O2 -tolerant alkaline protease produced from B. invictae AH1 with a molecular mass of about 41 kDa, noted P3, was purified by successive steps of ultrafiltration, gel filtration and ion exchange chromatography. The K m and Vmax values of the purified protease using casein, as substrate, were about 4 mg/mL and 27 µM/min, respectively. The highest enzyme activity was found at pH 9.0 and a temperature of 60°C. In addition, the enzyme showed a quasi-total stability against H2 O2 (5% for 1 hr) and against most of the tested solid and liquid detergents, suggesting its eventual use in bio-detergent formulations.

Impact of urbanisation (trends) on runoff behaviour of Pampulha watersheds (Brazil).

The paper presents an analysis of runoff behaviour of four urban catchments between the municipalities of Belo Horizonte and Contagem in Brazil, linked to their land use. Two years of online measurement of flow data, combined with spatial analysis, was linked through runoff modelisation with EPA SWMM. The coefficients of Nash obtained varying between 0.75 and 0.87 demonstrated an adequate modelling approach. A 1-year rain series was applied to evaluate the runoff behaviour of actual land cover and that of 2002. The peak flows normalised to watershed surfaces revealed as the most urbanised (85%) watershed Ressaca with 178 L/ha/s, three times more runoff intensive than the least urbanised (41%) Mergulhão with 67 L/ha/s. Statistical analysis of land cover data and modelling results on watershed and sub-watershed level showed main correlations between hydrological parameters such as peak flow, average event flow and restitution time, but also between land cover and runoff coefficient. This approach gave a linear relation between runoff and green surface, with a runoff coefficient of 0.86 for fully urbanised zone and 0.43 for full "green" cover. Prospective simulation with actual urbanisation rates varying from 4 to 34 ha/year suggested an increase between 6 and 18% of the flows and a possible end of urbanisation within the next two to three decades. These findings should contribute to a better understanding of hydrological impact of Belo Horizonte urbanisation and to the restauration of its Lake Pampulha.

Simultaneous cleanup of Reactive Black 5 and cadmium by a desert soil bacterium.

Multi-contaminated industrial wastewaters pose serious environmental risks due to high toxicity and non-biodegradability. The work reported here evaluated the ability of Pseudomonas aeruginosa strain Gb30 isolated from desert soil to simultaneously remove cadmium (Cd) and Reactive Black 5 (RB5), both common contaminants in various industrial effluents. The strain was able to grow normally and decolorize 50 mg L-1 RB5 within 24 h of incubation in the presence of 0.629 m mol L-1 of Cd2+. In order to evaluate strain performance in RB5 detoxification, a cytotoxicity test using Human Embryonic Kidney cells (HEK293) was used. Cadmium removal from culture media was determined using atomic adsorption. Even in presence of (0.115 + 0.157 + 0.401 + 0.381) m mol L-1, respectively, of Cr6+, Cd2+, Cu2+ and Zn2+ in the growth medium, strain Gb30 successfully removed 35% of RB5 and 44%, 36%, 59% and 97%, respectively, of introduced Zn2+, Cu2+, Cr6+ and Cd2+, simultaneously. In order to understand the mechanism of Cd removal used by P. aeruginosa strain Gb30, biosorption and bioaccumulation abilities were examined. The strain was preferentially biosorbing Cd on the cell surface, as opposed to intracellular bioaccumulation. Microscopic investigations using AFM, SEM and FTIR analysis of the bacterial biomass confirmed the presence of various structural features, which enabled the strain to interact with metal ions. The study suggests that Pseudomonas aeruginosa Gb30 is a potential candidate for bioremediation of textile effluents in the presence of complex dye-metal contamination.

Lawsonia inermis essential oil: extraction optimization by RSM, antioxidant activity, lipid peroxydation and antiproliferative effects.

BACKGROUND: The present study was focused on the optimization of yield of the essential oil extraction from leaves of Lawsonia inermis, and the determination of chemical composition, antioxidant activities, and lipid peroxydation and antiproliferative effects. METHODS: Henna essential oil (HeEO) were extracted by hydrodistillation; the identification of the chemical composition were done by GC/MS method. HeEO was analyzed for antioxidant power in: (1) chemical system by the DPPH test, the ABTS test and the total antioxidant activity test; and (2) in biological system by lipid peroxydation tests (MDA and DC) in cells culture. The cytotoxicity effects of HeEO were assessed using MTT assay against Raji and HeLa cell lines. RESULTS: The optimal extraction yield was 6.8 g/100 g d.b. HeEO showed a remarkable anti-oxidant activities including DDPH (42%), ABTS (87%) and the power of ammonium phosphomolybdate (2992 ± 230 mg of HeEO by equivalent to 1 mg of vitamin C in terms of total antioxidant power). CONCLUSION: Beyond notable antioxidant activities of the HeEo, our results showed a significant decrease in the production of ERO in the Raji cell line. The anti-tumor power of the Henna essential oil shows an interesting cytotoxicity effect (IC50 at 0.26 µg/mL for Raji and at 1.43 µg/mL for HeLa) with a total mortality percentage reaching 60%, for both.

Optimization of Cinnamon (Cinnamomum zeylanicum Blume) Essential Oil Extraction: Evaluation of Antioxidant and Antiproliferative Effects.

Having high cytotoxicity cell line effect, Cinnamomum zeylanicum Blume essential oil offers a novel approach to the chemotherapy treatment. In order to enhance its quantity/purity, the experimental conditions to produce essential oil should be more exploited. Steam distillation was used to isolate essential oil, and its conditions' optimization was carried out with the surface-response methodology. The maximum amount (2.6 g/100 g d.b.) was obtained under minimum condensation water flow (0.8 mL/min), a sample size of 6.5 cm, a saline solution concentration of 262.5 g/L, and five washings. The produced essential oil contains >77% of polyphenols. In vitro cytotoxicity was examined using an MTT assay against HeLa and Raji cell lines. The essential oil's capability to inhibit the proliferation of HeLa and Raji cell lines was studied under some conditions presenting IC50 values of 0.13 and 0.57 µg/mL, respectively. The essential oil was evaluated for its potential as an antioxidant by using in vitro models, such as phosphomolybdenum, DPPH, and H2O2 methods, in comparison with the synthetic antioxidant BHT (butylated hydroxytoluene) and ascorbic acid (vitamin C) as positive controls. The ammonium phosphomolybdate potency in the present study is of the order of 108.75 ± 32.63 mg of essential oil/equivalent to 1 mg of vitamin C in terms of antioxidant power, and the antioxidant activity of DPPH-H2O2 was 21.3% and 55.2%, respectively. The Cinnamomum zeylanicum Blume essential oil (CEO) covers important antioxidant and antiproliferative effects. This can be attributed to the presence of few minor and major phenolic compounds.

Prickly pear cactus cladodes powder of Opuntia ficus indica as a cost effective biosorbent for dyes removal from aqueous solutions.

The textiles manufacturing is one of the core industries that release a huge amount of dyes during the dyeing process. As a result, the growing demand of an efficient and low-cost treatment has given rise to alternative adsorbents. In the present study, prickly pear cactus cladodes powder (PPCP) of Opuntia ficus indica was investigated as an ecofriendly and low-cost biosorbent of Acid orange 51 (AO51) and Reactive Red 75 (RR75) dyes commonly used in dyeing. The FTIR spectroscopic characterization of PPCP showed the heterogeneity in surface structure and functional groups which confers to the biosorbent its capability to interact with acidic (AO51) and reactive (RR75) dyes molecules. Effects of pH, temperature, initial dye concentration and adsorbent dose on adsorption yield were investigated. The dyes uptake process was closely fitted to the pseudo-second order kinetic for both dyes. Experimental data were analyzed by applying the Langmuir, Freundlich, Dubinin-Raduskevich, Temkin, Redlich-Peterson, and BET isotherms equations. The models of BET and Langmuir were considered as the best isotherms models fitting experimental data, respectively, of RR75 and AO51. The maximum Langmuir monolayer biosorption capacities were of 198.9 and 45 mg g-1, respectively for RR75 and AO51.

Optimization of lipids' ultrasonic extraction and production from Chlorella sp. using response-surface methodology.

BACKGROUND: Three steps are very important in order to produce microalgal lipids: (1) controlling microalgae cultivation via experimental and modeling investigations, (2) optimizing culture conditions to maximize lipids production and to determine the fatty acid profile the most appropriate for biodiesel synthesis, and (3) optimizing the extraction of the lipids accumulated in the microalgal cells. METHODS: Firstly, three kinetics models, namely logistic, logistic-with-lag and modified Gompertz, were tested to fit the experimental kinetics of the Chlorella sp. microalga culture established on standard conditions. Secondly, the response-surface methodology was used for two optimizations in this study. The first optimization was established for lipids production from Chlorella sp. culture under different culture conditions. In fact, different levels of nitrate concentrations, salinities and light intensities were applied to the culture medium in order to study their influences on lipids production and determine their fatty acid profile. The second optimization was concerned with the lipids extraction factors: ultrasonic's time and temperature, and chloroform-methanol solvent ratio. RESULTS: All models (logistic, logistic-with-lag and modified Gompertz) applied for the experimental kinetics of Chlorella sp. show a very interesting fitting quality. The logistic model was chosen to describe the Chlorella sp. kinetics, since it yielded the most important statistical criteria: coefficient of determination of the order of 94.36%; adjusted coefficient of determination equal to 93.79% and root mean square error reaching 3.685 cells · ml- 1. Nitrate concentration and the two interactions involving the light intensity (Nitrate concentration × light intensity, and salinities × light intensity) showed a very significant influence on lipids production in the first optimization (p < 0.05). Yet, only the quadratic term of chloroform-methanol solvent ratio showed a significant influence on lipids extraction relative to the second step of optimization (p < 0.05). The two most abundant fatty acid methyl esters (≈72%) derived from the Chlorella sp. microalga cultured in the determined optimal conditions are: palmitic acid (C16:0) and oleic acid (C18:1) with the corresponding yields of 51.69% and 20.55% of total fatty acids, respectively. CONCLUSIONS: Only the nitrate deficiency and the high intensity of light can influence the microalgal lipids production. The corresponding fatty acid methyl esters composition is very suitable for biodiesel production. Lipids extraction is efficient only over long periods of time when using a solvent with a 2/1 chloroform/methanol ratio.