Hussein N. Nassar

Enhancing Biodegradation of Dibenzothiophene by Bacillus sphaericus HN1 Using Factorial Design and Response Surface Optimization of Medium Components

Abstract Based on four levels of full factorial design, a statistical design of experiments is used to investigate two cases of dibenzothiophene biodegradation in batch processes using Bacillus sphaericus HN1, involving as factors, yeast extract and dimethylsulfoxide or magnesium sulfate for first and second cases, respectively. Predictive models have been correlated finding out how significant the effects of these variables (factors) and their interactions are in practice. Also, response surface methodology has been applied to visualize the effect of the studied factors and LINGO software was used to find out the optimum values of the variables for enhancing the process.

Factorial Design and Response Surface Optimization for Enhancing a Biodesulfurization Process

Based on five levels of full factorial design, response surface methodology was used for modeling, optimization, and studying the interactive effects of two variables, nitrogen source and carbon co-substrate, in a batch process for dibenzothiophene biodesulfurization, using a new Gram-positive bacterial isolate R. erythropolis HN2 (accession no. KF018282). The optimum operating conditions were found to be 0.35 g/L yeast extract and 0.09 M glycerol.

Kinetic Modeling of the Bioremediation of Diesel Oil Polluted Seawater Using Pseudomonas aeruginosa NH1

In this study, the marine diesel oil-degrading bacterium strain NH1 was isolated and identified with respect to its 16S rDNA sequence as Pseudomonas aeruginosa with accession number KM267644. The ability of NH1 immobilized by entrapment in Ca-alginate gel to degrade different components of diesel oil contaminating seawater was examined in a batch system. The biodegradation rate of different components of diesel oil in free and immobilized cell systems can be ranked in the following decreasing order: total resolvable peaks (normal- and iso-alkanes) > the 16 polyaromatic hydrocarbons listed by the United States Environmental Protection Agency as priority pollutants > polyaromatic sulfur heterocyclic compounds > unresolved complex mixture (naphthenes, cyclo-alkanes, and aromatics). Kinetic modeling was performed to estimate the rate of biodegradation of each hydrocarbon type component. The biodegradation of diesel oil, total resolvable peaks and unresolved complex mixture was found to be best fitted with the second-order, while that of polyaromatic sulfur heterocyclic compounds and polyaromatic hydrocarbons followed the first-order kinetic model equations. The biodegradation rate of different components of diesel oil: aliphatics, polyaromatic sulfur heterocyclic compounds, and biomarkers (pristane, phytane, and 4,6-dimethyldibenzothiophene) was enhanced by immobilization, indicating the improved tolerance of the immobilized cells towards different toxic components of diesel oil. Storage stability and reusability tests revealed that the diesel oil degradation ability of the immobilized cells was stable after storage at 4°C for 30 d and can be effectively reused for two batches of 56 d.

Green synthesis of α-Fe2O3 using Citrus reticulum peels extract and water decontamination from different organic pollutants

ABSTRACT In this study, α-Fe2O3 nanoparticles (NPs) have been prepared using the hot water extract of the mandarin (Citrus reticulum) peels as a way for recycling of domestic waste to valuable product. The prepared hematite was characterized by UV/Vis spectroscopy, thermal gravimetric analysis, XRD, FTIR, SEM, and TEM. It was found to be porous irregular sphere shaped NPs with average size of 20–63 nm, characterized by weak ferromagnetic properties and band gap (Eg) of 2.38 eV. The prepared α-Fe2O3 NPs expressed good photocatalytic degradation activity. It showed good capacity for the decontamination of polluted water from anionic and cationic dyes and dicholorophenols under visible light irradiation.

Optimization of Libyan Crude Oil Biodegradation by Using Solid Waste Date as a Natural Low-Cost Material

The objective of this research was to evaluate the effectiveness of the use of solid waste date (SWD) as a lowcost natural agro-industrial materials, in improving crude oil biodegradation in contaminated sea water. Two types of Libyan crude oil (heavy crude oil (HCO) and light crude oil (LCO)) were used in this study. Batch reactors with sea water were used as bioreactors. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationship between operating variables, including HCO and LCO initial concentrations, SWD dosage, and incubation time, to determine the optimum operating conditions. Quadratic models of both CO biodegradation (%) were significant with very low probability values (<0.0001). The results indicated that under optimum operational conditions (i.e, SWD dosage of 0.21g/L in 11dayes for HCO and 0.20 g/L in 14 days for LCO), the best biodegradation efficiency of HCO and LCO were 79.49% and 94.15%, respectively. The predicted results of 82.10% and 95.45% fitted well with experimental results (HCO and LCO removal rates of 97.05% and 99.10%, respectively). Based on removal rates of 5.5% and 14.7% for both HCO and LCO without SWD, respectively, in 28 days, the obtained results revealed that SWD was very efficient in improving the biodegradation of high-concentration crude oils that contaminate sea water.

Modeling the relationship between microbial biomass and total viable count for a new bacterial isolate used in biodesulfurization of petroleum and its fractions

ABSTRACT Microbial parameters in a biodesulfurization batch process are often needed to be defined as mass (mg/mL) rather than total viable count (cells/mL) or optical density. This study illustrates mathematical correlations between different techniques used for following up the growth of a new biodesulfurizing bacterial isolate.

Response surface optimization of the thermal acid pretreatment of sugar beet pulp for bioethanol production using Trichoderma viride and Saccharomyces cerevisiae.

BACKGROUND Worldwide nowadays, relying on the second generation bioethanol from the lignocellulosic feedstock is a mandatory aim. However, one of the major drawbacks for high ethanol yield is the physical and chemical pretreatment of this kind of feedstock. As the pretreatment is a crucial process operation that modifies the lignocellulosic structure and enhances its accessibility for the high cost hydrolytic enzymes in an attempt to maximize the yield of the fermentable sugars. The objective of this work was to optimize and integrate a physicochemical pretreatment of one of the major agricultural wastes in Egypt; the sugar beet pulp (SBP) and the enzymatic saccharification of the pretreated SBP using a whole fungal cells with a separate bioethanol fermentation batch processes to maximize the bioethanol yield. METHODS AND RESULTS The response surface methodology was employed in this study to statistically evaluate and optimize the conditions for a thermal acid pretreatment of SBP. The significance and the interaction effects of the concentrations of HCl and SBP and the reaction temperature and time were studied using a three-level central composite design of experiments. A quadratic model equation was obtained to maximize the production of the total reducing sugars. The validity of the predicted model was confirmed. The thermally acid pretreated SBP was further subjected to a solid state fermentation batch process using Trichoderma viride F94. The thermal acid pretreatment and fungal hydrolyzes were integrated with two parallel batch fermentation processes of the produced hydrolyzates using Saccharomyces cerevisiae Y39, that yielded a total of ≈ 48 g/L bioethanol, at a conversion rate of ≈ 0.32 g bioethanol/ g SBP. CONCLUSION Applying the proposed integrated process, approximately 97.5 gallon of ethanol would be produced from a ton (dry weight) of SBP.

Applying Factorial Design and Response Surface Methodology to Enhance Microbial Denitrogenation by Tween 80 and Yeast Extract

In this study the effect of yeast extract as a conitrogen source and Tween 80 as a commercial and available nonionic surfactant on microbial denitrogenation MDN of carbazole by Bacillus clausii BS1 was investigated. The central composite design matrix and response surface methodology were applied in designing the batch experiments to evaluate the interactive effects of these two parameters on MDN. Quadratic model equations have been predicted finding out how significant the effects of these variables (factors) and their interactions are in practice. The validity of the predicted models was confirmed. The MDN efficiency increased from ≈88% without yeast extract or Tween 80 to ≈95% in presence of optimum concentration of 0.868 g/L yeast extract and 0.861% (v:v) Tween 80, which would represent a major economic improvement in low-margin, high-volume refining processes.

Enhancement of Carbazole Denitrogenation Rate Using Magnetically Decorated Bacillus clausii BS1

Bacillus clausii BS1 was coated by magnetic MFe3O4 nanoparticles (MNPs), and transmission electron microscope analysis of the cells showed that the MNPs were efficiently assembled and adsorbed on the surface of the microbial cell. The coated cells showed higher biodenitrogenation (BDN) rate toward CAR than that of the free cells, recording complete removal and 94.25% removal of 1000 ppm CAR within seven days, with t1/2 values of 31.36 and 64.78 h, respectively. Coated BS1 cells are characterized by higher BDN rate, storage and operational stabilities, and low sensitivity toward toxic by-products, and can be reused for four successive cycles without losing its biodenitrogenation efficiency and have the advantage of magnetic separation, which would resolve many operational problems in petroleum refinery.

Response Surface Optimization of Bioethanol Production from Sugarcane Molasses by Pichia veronae Strain HSC-22

Pichia veronae strain HSC-22 (accession number KP012558) showed a good tolerance to relatively high temperature, ethanol and sugar concentrations. Response surface optimization based on central composite design of experiments predicted the optimal values of the influencing parameters that affect the production of bioethanol from sugarcane molasses to be as follows: initial pH 5, 25% (w : v) initial molasses concentration, 35°C, 116 rpm, and 60 h. Under these optimum operating conditions the maximum bioethanol production on a batch fermenter scale was recorded as 32.32 g/L with 44% bioethanol yield.