Microbial synthesis of β-carotene has gained more interest as an alternative to synthetic β-carotene due to easy extraction and high yield. The vitamin microbial production is mainly dependent on culture conditions and the medium compositions. In this study, the β-carotene production by the Rhodo- torula glutinis ASU6 (KU550702) was evaluated under different growth conditions and nutrient composition. Different agro-renewable wastes were tested as carbon source for R. glutinis to obtain maximum amount of β-carotene. Meanwhile, it is clear that R. glutinis could grow well on acid extract of onion peels and produced large amount of β-carotene. Initial statistical screening using a Plackett-Burman design showed temperature, incubation time, fermentation type, non-treated onion waste, KH2PO4 and L-asparagine as significantly, influencing β-carotene production. Response surface methodology was applied to determine the mutual interactions between these parameters and optimal levels for β-carotene production. The maximum value of β-carotene production was 204.29 mg/l (7.5-fold) of value observed as central point of the central composite design. All the experimental data are in good agreement with predicted ones, confirming the responsibility of the proposed empirical model in describing β-carotene production by R. glutinis. In the whole, the outcomes of this study support the exploitation of onion peels through microbial fermentation for β-carotene production.

The current study aimed to improve riboflavin production by native bacterial isolates and medium components. Bacterial species Bacillus subtilis ASU8 (KU559874) and Bacillus tequilensis ASU9 (KU559876) showed high potentiality for riboflavin production. The optimal growth and riboflavin production were achieved after 48 h. The impact of glycine addation to the basal medium was explored by applying different concentrations (0.1-3 g/l). The addition of glycine was effective and the influencing concentration was 1 g/l giving 144.7 and184.2 mg/l yields of riboflavin for Bacillus subtilis ASU8 and Bacillus tequilensis ASU9, respectively. Medium constitu- ents were also optimized for high riboflavin yield using central composite design (CCD) of response surface methodology (RSM) to optimize the significant values and to study the mutual interactions between these constituents. The analysis revealed that optimal medium concentrations for maximum production of riboflavin by Bacillus subtilis (273.82 mg/l) and Bacillus tequilensis (288.33 mg/l) were (g/l): glucose 60, 40; NaNO 3 3, 5; KH 2 PO 4 2.5, 1.5; K 2 HPO 4 1, 0.5 and MgSO 4 .7H 2 0.1, 0.5 for Bacillus subtilis and Bacillus tequilensis , respectively. Analysis of variance results showed that the model was significant and an R2 value of 98.06% ( Bacillus sub- tilis ), 99.34% ( Bacillus tequilensis ) demonstrated that the experimental results were fitted well with predicted values. Optimization of medium conditions using RSM experimental design is an efficient approach for the production of riboflavin through microbial fermentation by Bacillus subtilis and Bacillus tequilensis could be utilized in industrial application

The current study aimed to improve riboflavin production by native bacterial isolates and medium components. Bacterial species Bacillus subtilis ASU8 (KU559874) and Bacillus tequilensis ASU9 (KU559876) showed high potentiality for riboflavin production. The optimal growth and riboflavin production were achieved after 48 h. The impact of glycine addation to the basal medium was explored by applying different concentrations (0.1-3 g/l). The addition of glycine was effective and the influencing concentration was 1 g/l giving 144.7 and184.2 mg/l yields of riboflavin for Bacillus subtilis ASU8 and Bacillus tequilensis ASU9, respectively. Medium constitu- ents were also optimized for high riboflavin yield using central composite design (CCD) of response surface methodology (RSM) to optimize the significant values and to study the mutual interactions between these constituents. The analysis revealed that optimal medium concentrations for maximum production of riboflavin by Bacillus subtilis (273.82 mg/l) and Bacillus tequilensis (288.33 mg/l) were (g/l): glucose 60, 40; NaNO 3 3, 5; KH 2 PO 4 2.5, 1.5; K 2 HPO 4 1, 0.5 and MgSO 4 .7H 2 0.1, 0.5 for Bacillus subtilis and Bacillus tequilensis , respectively. Analysis of variance results showed that the model was significant and an R2 value of 98.06% ( Bacillus sub- tilis ), 99.34% ( Bacillus tequilensis ) demonstrated that the experimental results were fitted well with predicted values. Optimization of medium conditions using RSM experimental design is an efficient approach for the production of riboflavin through microbial fermentation by Bacillus subtilis and Bacillus tequilensis could be utilized in industrial application

The current study aimed to improve riboflavin production by native bacterial isolates and medium components. Bacterial species Bacillus subtilis ASU8 (KU559874) and Bacillus tequilensis ASU9 (KU559876) showed high potentiality for riboflavin production. The optimal growth and riboflavin production were achieved after 48 h. The impact of glycine addation to the basal medium was explored by applying different concentrations (0.1-3 g/l). The addition of glycine was effective and the influencing concentration was 1 g/l giving 144.7 and184.2 mg/l yields of riboflavin for Bacillus subtilis ASU8 and Bacillus tequilensis ASU9, respectively. Medium constitu- ents were also optimized for high riboflavin yield using central composite design (CCD) of response surface methodology (RSM) to optimize the significant values and to study the mutual interactions between these constituents. The analysis revealed that optimal medium concentrations for maximum production of riboflavin by Bacillus subtilis (273.82 mg/l) and Bacillus tequilensis (288.33 mg/l) were (g/l): glucose 60, 40; NaNO 3 3, 5; KH 2 PO 4 2.5, 1.5; K 2 HPO 4 1, 0.5 and MgSO 4 .7H 2 0.1, 0.5 for Bacillus subtilis and Bacillus tequilensis , respectively. Analysis of variance results showed that the model was significant and an R2 value of 98.06% ( Bacillus sub- tilis ), 99.34% ( Bacillus tequilensis ) demonstrated that the experimental results were fitted well with predicted values. Optimization of medium conditions using RSM experimental design is an efficient approach for the production of riboflavin through microbial fermentation by Bacillus subtilis and Bacillus tequilensis could be utilized in industrial application

The current study aimed to improve riboflavin production by native bacterial isolates and medium components. Bacterial species Bacillus subtilis ASU8 (KU559874) and Bacillus tequilensis ASU9 (KU559876) showed high potentiality for riboflavin production. The optimal growth and riboflavin production were achieved after 48 h. The impact of glycine addation to the basal medium was explored by applying different concentrations (0.1-3 g/l). The addition of glycine was effective and the influencing concentration was 1 g/l giving 144.7 and184.2 mg/l yields of riboflavin for Bacillus subtilis ASU8 and Bacillus tequilensis ASU9, respectively. Medium constitu- ents were also optimized for high riboflavin yield using central composite design (CCD) of response surface methodology (RSM) to optimize the significant values and to study the mutual interactions between these constituents. The analysis revealed that optimal medium concentrations for maximum production of riboflavin by Bacillus subtilis (273.82 mg/l) and Bacillus tequilensis (288.33 mg/l) were (g/l): glucose 60, 40; NaNO 3 3, 5; KH 2 PO 4 2.5, 1.5; K 2 HPO 4 1, 0.5 and MgSO 4 .7H 2 0.1, 0.5 for Bacillus subtilis and Bacillus tequilensis , respectively. Analysis of variance results showed that the model was significant and an R2 value of 98.06% ( Bacillus sub- tilis ), 99.34% ( Bacillus tequilensis ) demonstrated that the experimental results were fitted well with predicted values. Optimization of medium conditions using RSM experimental design is an efficient approach for the production of riboflavin through microbial fermentation by Bacillus subtilis and Bacillus tequilensis could be utilized in industrial application

The northwestern part of Suez Gulf region is a strategic area in Egypt. It includes important sources of national income. To achieve the development goals, the government has established huge projects in this area (e.g. establishment and expanding of a large commercial port at Ain Sokhna, many industrial zones as well as tourism projects). The utilization of the Suez Gulf resources and their continuing development mainly depend on the creation of actual pollution control programs. The environmental quality control and pollution reduction activities are important ingredients of any economic development program. These different activities in this area depend mainly on the groundwater that is pumped intensively from different water bearing formations or aquifers. The main objective of the present work is compiling the previous studies from the 1980s up to 2015. These studies are concerned with estimating the concentrations of different pollutants in various ecosystems in the northwestern Suez Gulf region. Also, to provide an explanation for the movement of different pollutants such as organic and heavy metals from contaminated land to ground and surface (Gulf) waters. This issue has not been extensively surveyed before, and this review, gives specific directions for future monitoring and remediation strategies in this region.

The photoluminescence of Gd-doped GaN multi-quantum wells (MQWs) is presented and discussed considering the formation of a Gd3+:Nitrogen-vacancy (N-vacancy) complex. A lower energy photoluminescence peak was observed for the Gd-doped GaN MQW sample with respect to the main peak assigned to a neutral donor bound exciton (D0X) of the undoped GaN MQW sample. The X-ray absorption near edge structure spectrum observed at Gd LIII-edge indicates a nitrogen vacancy adjacent to the Gd substituting the Ga ion in Gd-doped GaN MQW sample. Local stresses around the Gd dopants in Gd-doped GaN matrix generated due to the larger diameter of the Gd3+ ion with respect to the Ga3+ ion can be relieved by the creation of vacancies. The lower formation energy of N-vacancies in GaN matrix introduce them as a preferred candidate to relieve the generated stresses. A Gd3+:N-vacancy complex consisting of a Gd3+ ion and the created nitrogen vacancy adjacent to the Gd3+ dopant is likely to form in GaN:Gd matrix. The lower photoluminescence peak energy observed in the Gd-doped GaN MQW sample is assigned to the recombination of an exciton captured at the Gd3+:N-vacancy complex forming a small polaron-like state. A model is presented considering the small exciton-polaron population in defect sites captured around the Gd3+ ions in the Gd-doped GaN.

ZnO nanopowders were successfully synthesized by the ice-bath assisted sonochemical method. The nanopowders were annealed in air for 3 h at different annealing temperatures (Ta) ranging from 300 to 700 °C. The effect of Ta on the structural and morphological properties was investigated by the x-ray diffraction (XRD) and the transmission electron microscopy (TEM). The optical properties were studied by recording the optical absorption and photoluminescence (PL) spectra. The XRD analysis showed that the thermal annealing leads to an improvement in the crystallinity associated with an increase in the crystallite size as well as an increase in both the Zn-O bond length and unit cell volume. Also, it was found that the increase of Ta results in a shift in the diffraction angle toward lower values associated with a decrease in the micro-strain. The morphological study confirms that the samples are mixtures of nanosheets and nanorods. In addition, the length and diameter of the nanorods increase as the annealing temperature increases. The optical absorption spectra show that the exciton peak of the as-prepared sample is red shifted from 370 to 378 nm by thermal annealing, and the optical band gap decreases from 3.45 to 3.36 eV. The photoluminescence spectra were reordered at an excitation wavelength of 325 nm, and the deconvolution of the spectra reveals four emission bands where the main UV band (at λ=397 nm) can be attributed to exciton recombination related to near-band-edge. Furthermore, the thermal annealing results in a reduction of the PL intensity of the annealed samples.

ZnO nanopowders were successfully synthesized by the ice-bath assisted sonochemical method. The nanopowders were annealed in air for 3 h at different annealing temperatures (Ta) ranging from 300 to 700 °C. The effect of Ta on the structural and morphological properties was investigated by the x-ray diffraction (XRD) and the transmission electron microscopy (TEM). The optical properties were studied by recording the optical absorption and photoluminescence (PL) spectra. The XRD analysis showed that the thermal annealing leads to an improvement in the crystallinity associated with an increase in the crystallite size as well as an increase in both the Zn-O bond length and unit cell volume. Also, it was found that the increase of Ta results in a shift in the diffraction angle toward lower values associated with a decrease in the micro-strain. The morphological study confirms that the samples are mixtures of nanosheets and nanorods. In addition, the length and diameter of the nanorods increase as the annealing temperature increases. The optical absorption spectra show that the exciton peak of the as-prepared sample is red shifted from 370 to 378 nm by thermal annealing, and the optical band gap decreases from 3.45 to 3.36 eV. The photoluminescence spectra were reordered at an excitation wavelength of 325 nm, and the deconvolution of the spectra reveals four emission bands where the main UV band (at λ=397 nm) can be attributed to exciton recombination related to near-band-edge. Furthermore, the thermal annealing results in a reduction of the PL intensity of the annealed samples.

ZnO nanopowders were successfully synthesized by the ice-bath assisted sonochemical method. The nanopowders were annealed in air for 3 h at different annealing temperatures (Ta) ranging from 300 to 700 °C. The effect of Ta on the structural and morphological properties was investigated by the x-ray diffraction (XRD) and the transmission electron microscopy (TEM). The optical properties were studied by recording the optical absorption and photoluminescence (PL) spectra. The XRD analysis showed that the thermal annealing leads to an improvement in the crystallinity associated with an increase in the crystallite size as well as an increase in both the Zn-O bond length and unit cell volume. Also, it was found that the increase of Ta results in a shift in the diffraction angle toward lower values associated with a decrease in the micro-strain. The morphological study confirms that the samples are mixtures of nanosheets and nanorods. In addition, the length and diameter of the nanorods increase as the annealing temperature increases. The optical absorption spectra show that the exciton peak of the as-prepared sample is red shifted from 370 to 378 nm by thermal annealing, and the optical band gap decreases from 3.45 to 3.36 eV. The photoluminescence spectra were reordered at an excitation wavelength of 325 nm, and the deconvolution of the spectra reveals four emission bands where the main UV band (at λ=397 nm) can be attributed to exciton recombination related to near-band-edge. Furthermore, the thermal annealing results in a reduction of the PL intensity of the annealed samples.