Hassan Gomaa

Investigation of a dual‐particle liquid–solid circulating fluidized bed bioreactor for extractive fermentation of lactic acid

A dual‐particle liquid–solid circulating fluidized bed (DP‐LSCFB) bioreactor has been constructed and investigated for the simultaneous production and extraction of lactic acid using immobilized Lactobacillus bulgaricus and ion‐exchange resins. The apparatus consisted of a downer fluidized bed, 13 cm I.D. and 4.75 m tall, and a riser fluidized bed, 3.8 cm I.D. and 5.15 m in height. The lactic acid production and removal was carried out in the downer, while the riser was used for the recovery of lactic acid. A continuously recirculating bed of ion‐exchange resin was used for adsorption of the produced acid as well as for maintaining optimum pH for bioconversion, thus eliminating the need for costly and complex chemical control approach used in conventional techniques. Studies using lactic acid aqueous solution as feed and sodium hydroxide solution as regeneration stream showed 93% lactic acid removal from the downer and 46% recovery in the riser under the conditions investigated. Such results prove the functionality of using the newly developed bioreactor design for the continuous production and recovery of products of biotechnological significance.

Sacrificial hydrogen generation from aqueous triethanolamine with Eosin Y-sensitized Pt/TiO2 photocatalyst in UV, visible and solar light irradiation.

In this paper, we have studied Eosin Y-sensitized sacrificial hydrogen generation with triethanolamine as electron donor in UV, visible, and solar light irradiation. Aeroxide TiO2 was loaded with platinum metal via solar photo-deposition method to reduce the electron hole recombination process. Photocatalytic sacrificial hydrogen generation was influenced by several factors such as platinum loading (wt%) on TiO2, solution pH, Eosin Y to Pt/TiO2 mass ratio, triethanolamine concentration, and light (UV, visible and solar) intensities. Detailed reaction mechanisms in visible and solar light irradiation were established. Oxidation of triethanolamine and formaldehyde formation was correlated with hydrogen generation in both visible and solar lights. Hydrogen generation kinetics followed a Langmuir-type isotherm with reaction rate constant and adsorption constant of 6.77×10(-6) mol min(-1) and 14.45 M(-1), respectively. Sacrificial hydrogen generation and charge recombination processes were studied as a function of light intensities. Apparent quantum yields (QYs) were compared for UV, visible, and solar light at four different light intensities. Highest QYs were attained at lower light intensity because of trivial charge recombination. At 30 mW cm(-2) we achieved QYs of 10.82%, 12.23% and 11.33% in UV, visible and solar light respectively.

Resolution of sertraline with (R)-mandelic acid: Chiral discrimination mechanism study

The chiral discrimination mechanism in the resolution of sertraline with mandelic acid was investigated by examining the weak intermolecular interactions (such as hydrogen bond, CH/π, and van der Waals interactions) and molecular packing difference in crystal structures of the resulting diastereomeric salts. A new one-dimensional chain-like hydrogen-bonding network and unique supramolecular packing mode are disclosed. The investigation demonstrated that stable hydrogen-bonding pattern, herringbone-like arrangement of aromatic rings, and planar boundary surface in the hydrophobic region are the three most important structural characteristics expected in less soluble diastereomeric salts. The existence and magnitude of hydrogen bond, CH/π interaction, and van der Waals interaction related to three characteristic structures, determine the stability of diastereomeric salt. The hydrogen bond is not necessarily the dominant factor while the synergy and optimization of all weak intermolecular interactions attribute to the chiral recognition.

Chiral discrimination in diastereomeric salts of chlorine-substituted mandelic acid and phenylethylamine

The crystal structures of diastereomeric salts of chloromandelic acid and phenylethylamine were determined and are presented herein. The structure comparison between less soluble salts and more soluble salts shows that weak interactions such as CH/pi interactions and van der Waals gain importance and contribute to chiral recognition when the hydrogen bonding patterns are very similar.

Identification and Characterization of Solid-State Nature of 2-Chloromandelic Acid

The racemate and enantiomers of 2-chloromandelic acid were characterized by SS-NMR, XRPD, and FTIR. The binary melting point phase diagram was constructed by DSC (differential scanning calorimetry). The solid-state nature of 2-chloromandelic acid was identified to be a racemic compound. The crystal structure of racemic compound was determined to be monoclinic P2(1)/c.

Bioactivity of Hybrid Polymeric Magnetic Nanoparticles and Their Applications in Drug Delivery.

BACKGROUND Engineered magnetic nanoparticles (MNPs) possess unique properties and hold great potential in biomedicine and clinical applications. With their magnetic properties and their ability to work at cellular and molecular level, MNP have been applied both in-vitro and in-vivo in targeted drug delivery and imaging. Focusing on Iron Oxide Superparamagnetic nanoparticles (SPIONs), this paper elaborates on the recent advances in development of hybrid polymeric-magnetic nanoparticles. Their main applications in drug delivery include Chemotherapeutics, Hyperthermia treatment, Radio-therapeutics, Gene delivary, and Biotheraputics. Physiochemical properties such as size, shape, surface and magnetic properties are key factors in determining their behavior. Additionally tailoring SPIONs surface is often vital for desired cell targetting and improved efficiency. Polymer coating is specifically reviewed with brief discussion of SPIONs administration routes. Commonly used drug release models for describing release mechanisms and the nanotoxicity aspects are also discussed. METHODS This review focus on superparamagnetic nanoparticles coated with different types of polymers starting with the key physiochemical features that dominate their behavior. The importance of surface modification is addressed. Subsequently, the major classes of polymer modified iron oxide nanoparticles is demonstrated according to their clinical use and application. Clinically approved nanoparticles are then addressed and the different routes of administration are mentioned. Lastly, mathematical models of drug release profile of the common used nanoparticles are addressed. RESULTS MNPs emerging in recent medicine are remarkable for both imaging and therapeutics, particularly, as drug carriers for their great potential in targeted delivery and cancer treatment. Targeting ability and biocompatibility can be improved though surface coating which provides a mean to alter the surface features including physical characteristics and chemical functionality. The use of biocompatible polymers can prevent aggregation, increase colloidal stability, evades nanoparticles uptake by RES, and can provide a surface for conjugation of targeting ligands such as peptide and biomolecules with high affinity to target cells. CONCLUSION Great efforts to bring MNPs from lab testing stage to clinic are needed to understand their physicochemical properties and how they behave in vivo, which resulted in few of them to exist in the market today. Although magnetic nanoparticles have not yet fully reached their optimal safety and efficiency due to the challenges they face in vivo, their shortcomings can be overcome through improvement of magnetictargeted carrier by pre-clinical trials and continuous studies.

Flux Characteristics of Oil Separation from O/W Emulsions using Highly Hydrophilic UF Membrane in Narrow Channel

Flux characteristics of oil separation from O/W emulsions using highly hydrophilic polymeric UF membrane has been investigated. The effect of using sub-millimeter filtration channel on both unsteady and steady state permeate flux is evaluated. The time-dependent flux characteristics indicated that membrane fouling has proceeded mainly according to the intermediate pore blocking mechanism modified for crossflow filtration. The steady state flux increased initially with the transmembrane pressure (TMP), then reached a plateau at a relatively low TMP of ∼15 kPa, beyond which a steady operation was achieved, and there were practically no advantages of increasing the TMP. The pressure independent limiting flux increased with increasing the crossflow velocity and was found to scale with the membrane surface shear rate to the power of 0.35. The data were modeled satisfactorily using a dimensionally consistent semi-empirical model with R2 value of 0.96.

(R)-1-Phenyl­ethanaminium (S)-4-chloro­mandelate

The absolute configuration of the title complex, C(8)H(12)N(+)·C(8)H(6)ClO(3) (-) or [R-C(6)H(5)C(H)CH(3)NH(3)][S-4-ClC(6)H(4)C(H)(OH)CO(2)], has been confirmed by the structure determination. In the crystal structure, inter-molecular O-H⋯O and N-H⋯O hydrogen bonds form a two-dimensional network perpendicular to the c axis.

ANALYSIS OF AXIAL MIXING IN A GAS-LIQUID RECIPROCATING PLATE COLUMN

Axial mixing in the continuous phase in a Landau reciprocating-plate column (LRPC) has been investigated for both single-phase and two-phase gas-liquid flow conditions. A hydrodynamic model is proposed in which axial mixing is described as a process consisting of a backflow through the plate plus longitudinal mixing within the stage. The region in the proximity of the plates is almost perfectly mixed, beyond which there is a low-intensity mixing zone that varies in height and degree of mixing depending on phase velocities as well as the plates design and oscillation velocity. The presence of the dispersed phase affects axial mixing in both the well- and poorly mixed regions of each stage in two opposite ways: it decreases the backflow between the stages due to the hindrance effect caused by the presence of gas bubbles, and it increases the axial dispersion coefficient in the second stage by increasing the turbulence and phase entrainment caused by circulation and bubbles rising. The model adjustable parameters were determined from an experimentally measured dispersion coefficient over a wide range of operating conditions using the transient tracer injection method. The predictions of the model compare favorably with experimental data and can be applied for describing axial mixing in the continuous phase in an LRPC with±14% accuracy.

Emulsification Characteristics Using a Dynamic Woven Metal Microscreen Membrane

An oscillatory emulsification system for the production of oil in water emulsions using a commercially available low-cost woven metal microscreen (WMMS) is investigated. The system allows for independent control of both the oscillation frequencies and amplitudes such that it provides two degrees of freedom for controlling the emulsion properties. The investigations included the production of both surfactant and particle-stabilized emulsions. The average droplet size was found to decrease when both the oscillation frequency and amplitude was increased. For surfactant-stabilized emulsions, using bi-surfactants in both the continuous and dispersed phases resulted in a smaller droplet size due to lower interfacial tension. For particle-stabilized emulsions, both the hydrodynamics of the system and the hydrophobic and hydrophilic nature of the stabilizing particles influenced the interfacial properties at the oil–water interface, which in turn affected the final droplet size and distribution with potential droplet breakage. In absence of the latter, a simple torque balance model can be used to reasonably predict the average emulsion droplet size.