Economic production of Bacillus subtilis SPB1 biosurfactant using local agro‐industrial wastes and its application in enhancing solubility of diesel

BACKGROUND: The present work aimed to optimize a new economic medium for lipopeptide biosurfactant production by Bacillus subtilis SPB1 for application in the environmental field as an enhancer of diesel solubility. Statistical experimental designs and response surface methodology were employed to optimize the medium components. RESULTS: A central composite design was applied to increase the production yield and predict the optimal values of the selected factors. An optimal medium, for biosurfactant production of about 4.5 g L^?1, was found to be composed of sesame peel flour (33 g L^?1) and diluted tuna fish cooking residue (40%) with an inoculum size of 0.22. Increased inoculum size (final OD₆₀₀) significantly improved the production yield. The emulsifier produced was demonstrated to be an alternative to chemically synthesized surfactants since it shows high solubilization efficiency towards diesel oil in comparison with SDS and Tween 80. CONCLUSION: Optimization studies led to a strong improvement in production yield. The emulsifier produced, owing its high solubilization capacity and its large tolerance to acidic and alkaline pH values and salinity, shows great potential for use in bioremediation processes to enhance the solubility of hydrophobic compounds. © 2012 Society of Chemical Industry     

Sn doping effects on properties of ZnO thin films deposited by RF magnetron sputtering using a powder target

In the present study, tin doped ZnO thin films (ZnO:Sn) at different contents (0–3 wt%) were deposited onto glass substrates by RF magnetron sputtering using a powder compacted target at room temperature. The effect of Sn concentration on the structural, optical and electrical properties of the ZnO:Sn thin films were investigated. The X-ray diffraction analysis shows that the pure ZnO thin film exhibits a strong intensity of the (002) peak indicating a preferential orientation along the c-axis. For Sn doped ZnO thin films, there is a change in the orientation from the (002) plane to the (101) one. The undoped ZnO thin films have transmittance 85% in the visible range and slightly increased for 0.5 wt% of Sn, while it get decreased with further increasing the Sn doping concentration. The optical band gap energy get increased with increasing the doping concentration. Moreover, the electrical conductivity and conduction mechanism are also studied by impedance spectroscopy in the frequency range of 1KHz–13 MHz at various temperatures (633–743 K). The AC conductivity in ZnO thin films increased with angular frequency. The frequency exponent S decreases with increasing temperature. Such behavior suggests that the correlated barrier hopping (CBH) model may be suitable to explain the conduction mechanism in ZnO thin films. The activation energy values calculated from angular frequency and DC conductivity are in good agreement confirming that the conduction mechanism is thermally activated by hopping between localized states.     

Screening and optimization of the factors of a detergent admixture preparation

The present research studies the optimization of the preparation of a hydrotrope (mixture of sodium toluenesulfonate and sodium xylenesulfonates) for liquid detergents using experimental designs. The preparation is carried out by selective sulfonation of toluene and xylene present in the BTX fraction of a natural gas. The optimization of five responses has been carried out in two steps. First, we carry out an asymmetrical screening design 2¹3⁶//18 to select from seven factors, those factors which have significant influence on the amount of residual sodium sulfate in the product and on the total conversion of toluene and xylenes. Secondly, we carry out a Box–Behnken design to optimize three retained factors (temperature, molar ratio of acid to toluene plus xylenes, and the amount of desulfation agent), using response surface methodology. In addition, and in order to reach near-optimal sulfonation conditions, we use the desirability functions to optimize the five responses simultaneously. This allows us to determine for the whole process, sulfonation conditions leading to a high yield of toluene and xylene conversion and acceptable amounts of residual sodium sulfates and sodium benzenesulfonate.     

Characterization of the Tunisian blast-furnace slag and its application in the formulation of a cement

The Tunisian blast-furnace slag has been characterized by several physicochemical methods to evaluate its hydraulic reactivity. It has been noted that nearly all the slag is glassy, so its use as a replacement of cement is possible.This result has been confirmed by different physical tests applied to blended cements as specific surface, normal consistency, setting time, stability to expansion and the minislump.Finally, a slag cement composition has been formulated and optimized using a mixture design. The optimized formula giving the maximum of compressive strength at 7 and 28 days was 61% clinker, 35% slag, 3% gypsum, and 1% limestone.     

The analysis of crude and purified locust bean gum: A comparison of samples from different carob tree populations in Tunisia

The crude and purified locust bean gum (LBG) from seven areas of the north and centre of Tunisia (Bouarada, Bargou, Kessra, Haffouz, Borj Toumi, Ben Arous and INRGREF) were analyzed for moisture, ash, protein, acid-insoluble matter and mannose/galactose ratio. The purified samples exhibited higher mannose/galactose ratios and lower amounts of ash, protein and acid-insoluble matter than the crude gum. The purified LBG from different regions had 3.43–6.99% moisture, 0.87–2.06% ash, 0.61–2.46% protein, 0.00–1.20% acid-insoluble matter and 3.55–4.32 mannose/galactose ratios. Statistical analysis revealed that purification significantly affected (P < 0.05) moisture, ash, protein, insoluble matter contents and mannose/galactose ratios of the crude LBG and purified LBG for all samples from different areas. The rheological properties of the different carob gum samples were determined, the best rheological properties are those of spontaneous carob trees of Bargou, Bouarada and Kessra areas. The climatic and geographic origin of carob and the cultivation mode influence the chemical and rheological properties. The purification of crude galactomannan samples by precipitation with isopropanol gave a clear and more stable solution, due to the elimination of impurities and endogenous enzymes.     

Supersaturated design for screening factors influencing the preparation of sulfated amides of olive pomace oil fatty acids

In a previous paper, we showed that the preparation of sulfated diethanolamide of fatty acids is easy to carry out without organic solvents when using olive pomace oil as starting material; the reaction yield was, however, highly variable as a function of factor levels. The purpose of this research is to look for the optimal experimental conditions. We started by applying a supersaturated experimental design to screen for important factors among a list of 31 potentially influential factors in 18 experiments. Thus, we constructed a two-level supersaturated design as a half fraction of a 36-experiment Hadamard matrix and used it for this screening purpose. Multiple regression methods namely stepwise selection procedure, ridge regression and all-subset regressions were used to analyze the supersaturated design results according to a four step procedure. Results indicated that six factors, namely, molar ratio SO₃/ester, amidation time, amide addition rate, alkali reagent, alkali concentration, and amidation temperature, were very influential factors. Three other factors were moderately influential: neutralization temperature, sodium methanoate amount, and methanol amount. In future research, these factors will be further studied in order to perform robustness tests of the process.     

Fungal β-1,3-1,4-glucanases: production,proprieties and biotechnological applications

β-1,3-1,4-glucanases (or lichenases; EC 3.2.1.73) comprise one of the main enzymes used in industry during recent decades. These enzymes hydrolyze β-glucans containing β-1,3 and β-1,4 linkages, such as cereal β-glucans and lichenan. The β-1,3-1,4-glucanases are produced by a variety of bacteria, fungi, plants and animals. A large number of microbial β-1,3-1,4-glucanases have potential application in industrial processes, such as feed, food and detergent industries. The present review summarizes the available studies with respect to β-1,3-1,4-glucanases production conditions, enzyme biochemical properties and potential industrial application. © 2018 Society of Chemical Industry