Ashraf F. El-Baz

Technological advances in CO2 conversion electro-biorefinery: A step toward commercialization.

The global atmospheric warming due to increased emissions of carbon dioxide (CO2) has attracted great attention in the last two decades. Although different CO2 capture and storage platforms have been proposed, the utilization of captured CO2 from industrial plants is progressively prevalent strategy due to concerns about the safety of terrestrial and aquatic CO2 storage. Two utilization forms were proposed, direct utilization of CO2 and conversion of CO2 to chemicals and energy products. The latter strategy includes the bioelectrochemical techniques in which electricity can be used as an energy source for the microbial catalytic production of fuels and other organic products from CO2. This approach is a potential technique in which CO2 emissions are not only reduced, but it also produce more value-added products. This review article highlights the different methodologies for the bioelectrochemical utilization of CO2, with distinctive focus on the potential opportunities for the commercialization of these techniques.

Production of β-Glucosidase by Aspergillus niger on Wheat Bran and Glycerol in Submerged Culture: Factorial Experimental Design and Process Optimization

The goal of this study was to develop a fermentation process for the production of β-glucosidase, an important enzyme in the hydrolysis of lignocellulose and has many applications in food and flavor industries, using low-cost agricultural residues as substrates. Based on statistical experimental design, high-titer production of β-glucosidase on wheat bran and glycerol by Aspergillus niger in a submerged culture was achieved. A 2-level Plackett-Burman design was first used to screen the bioprocess parameters affecting β-glucosidase production. Among the tested parameters, the concentrations of wheat bran, glycerol, corn steep liquor and KCl showed significant effects on β-glucosidase production. These four medium components were further optimized using a 3-level Box-Behnken design, and their optimal levels were found to be: wheat bran, 3.5 g/L; glycerol, 5 g/L; KCl, 0.1 g/L and corn steep liquor, 7.5 g/L, giving a high βglucosidase titer of 9.37 IU/ml, 1.6-fold of the maximum level obtained in the screening experiment. With the optimized medium, 5.41 IU/ml of β-glucosidase was produced in a stirred-tank bioreactor inoculated with a spore suspension. When the reactor was inoculated with precultured cell pellets and operated at optimized agitation (450 rpm) and aeration rates (2 vvm), β-glucosidase production increased to 9.33 IU/ml, which was comparable to the level obtained in shake-flasks. This study demonstrated a scalable fermentation process for the production of β-glucosidase on low-cost wheat bran and glycerol, which should have important industrial applications.

Trichosporon jirovecii-mediated synthesis of cadmium sulfide nanoparticles.

Cadmium sulphide is one of the most promising materials for solar cells and of great interest due to its useful applications in photonics and electronics, thus the development of bio‐mediated synthesis of cadmium sulphide nanoparticles (CdS NPs) is one of the essential areas in nanoparticles. The present study demonstrates for the first time the eco‐friendly biosynthesis of CdS NPs using the yeast Trichosporon jirovecii. The biosynthesis of CdS NPs were confirmed by UV‐Vis spectrum and characterized by X‐ray diffraction assay and electron microscopy. Scanning and transmission electron microscope analyses shows the formation of spherical CdS NPs with a size range of about 6–15 nm with a mean Cd:S molar ratio of 1.0:0.98. T. jirovecii produced hydrogen sulfide on cysteine containing medium confirmed by positive cysteine‐desulfhydrase activity and the colony color turned yellow on 0.1 mM cadmium containing medium. T. jirovecii tolerance to cadmium was increased by the UV treatment and three 0.6 mM cadmium tolerant mutants were generated upon the UV radiation treatment. The overall results indicated that T. jirovecii could tolerate cadmium toxicity by its conversion into CdS NPs on cysteine containing medium using cysteine‐desulfhydrase as a defense response mechanism.

Kinetic Properties and Role of Bacterial Chitin Deacetylase in the Bioconversion of Chitin to Chitosan

Chitin is an extremely insoluble material with very limited industrial use; however it can be deacetylated to soluble chitosan which has a wide range of applications. The enzymatic deacetylation of various chitin samples was investigated using the bacterial chitin deacetylase (CDA), which was partially purified from Alcaligenes sp. ATCC 55938 growth medium and the kinetic parameters of the enzyme were determined. Also, the efficiency of biocatalyst recycling by immobilization technique was examined. CDA activity reached its maximum (0.419 U/ml) after 18 h of bacterial cultivation. When glycol chitin was used as a substrate, the optimum pH of the enzyme was estimated to be 6 after checking a pH range between 3 and 9, while the optimum temperature was found to be 35°C. Addition of acetate (100 mM) in the assay mixture resulted in 50% loss of enzyme activity. The Km value of the enzyme is 1.6 × 10(-4) µM and Vmax is 24.7 µM/min. The average activity of CDA was 0.38 U/ml for both of immobilized and freely suspended cells after 18 h of bacterial growth. Some related patents are also discussed here.

Fabrication and Characterization of Fungal Chitosan-SAP Membranes for Hemostatic Application

Novel membranes were fabricated from fungal chitosan (Cs) and starch based super absorbent polymer (SAP) for hemostatic application. The commercial production of Cs through alkaline deacetylation of crustacean chitin includes many drawbacks. Fungal Cs production, by a more eco-compatible technique, has become an alternative source for the traditional one. In this study, the production of fungal Cs was executed in a bioreactor from the mycelia of Absidia coerulea. The maximum obtained fungal Cs was 0.55 g/L after 48 h. The fabrication of Cs-SAP membranes was approached subsequently using two methods, physical blend of two polymers, and Cs-SAP sub-layer. To evaluate the homeostatic effect of Cs SAP membranes on blood, erythrocyte sedimentation test was conducted in vitro. Since increasing the Cs concentration from 0.5 to 2 % w/v in the fabricated Cs SAP membranes, reduces the erythrocyte sedimentation time from 69.8 to 62.3 min, respectively, while increasing the concentration of SAP (0.12-0.5 % w/v) has less or no significant effect on erythrocyte sedimentation time. Sub-layered 2L8 membrane significantly reduced ESR (P< 0.05) by 22%, while physically blended 11B8 membrane diminished ESR by only 12% compared to the control. Furthermore, these membranes were investigated by FT-IR, SEM, tensile, antimicrobial activity and cytotoxicity. Chitosan-SAP membranes can be described as bio-membranes with a homogeneous matrix, stable structure and interesting mechanical properties, with great possibilities of utilization in hemostasis.

Nanometals appraisal in food preservation and food-related activities

Nanomaterial synthesis, formulation, application, and evaluation were very motivating and promising areas for scientific research in the past years. Nanometals, because of their exciting biochemical activities, are powerful antimicrobial agents, especially against foodborne and phytopathogenic microorganisms. This suggested their recruitment as potential food preservatives and additives in food-related sectors, in individual forms, or in combination with other preservatives. The range of food-related activities, to exploit nanometals, include agrochemicals saving and improvements, enhancement of nutrients absorption, quality preservation, shelf-life extension, food security, traceability enhancement, food hygiene insurance, water desalination, and decontamination. Different antimicrobial modes of action are supposed to specify nanometals action toward microbial species. The biosafety issues and consumers potential risks, regarding nanometals supplementation, are addressed, including the consumers’ exposure, toxicity, toxicokinetics, and environmental contamination. This chapter attempts to cover the aforementioned topics, considering the potential advantages and drawbacks from the application of nanometals in food preservation.

Toward Enhancing the Enzymatic Activity of a Novel Fungal Polygalacturonase for Food Industry: Optimization and Biochemical Analyses

BACKGROUND The review of literature and patents shows that enhancing the polygalacturonase (PG) production and activity are still required to fulfill the increasing demands. METHODS A dual optimization process, which involved Plackett-Burman design (PBD), with seven factors, and response surface methodology, was applied to optimize the production of extracellular PG enzyme produced by a novel strain of Aspergillus flavus isolated from rotten orange fruit. The fungal PG was purified and biochemically characterized. RESULTS Three variables (harvesting time, pH and orange pomace concentration), that were verified to be significant by the PBD analysis, were comprehensively optimized via Box-Behnken design. According to this optimization, the highest PG activity (4073 U/mL) was obtained under pH 7 after 48 h using 40 g/L orange pomace as a substrate, with enhancement in PG activity by 51% compared to the first PBD optimization step. The specific activity of the purified PG was 1608 U/mg with polygalacturonic acid and its molecular weight was 55 kDa. The optimum pH was 5 with relative thermal stability (80%) at 50˚C after 30 min. The PG activity improved in the presence of Cu2+ and Ca2+, while Ba2+, Fe2+ and Zn2+ greatly inhibited the enzyme activity. The obvious Km and Vmax values were 0.8 mg/mL and 2000 μmol/min, respectively. CONCLUSION This study is a starting point for initial research in the field of optimization and characterization of A. flavus PG. The statistical optimization of A. flavus PG and its biochemical characterization clearly revealed that this fungal strain can be a potential producer of PG which has a wide range of industrial applications.

Biochemical and biotechnological studies on a novel purified bacillus cholesterol oxidase tolerant to solvent and thermal stress

Abstract A novel bacterial strain was isolated and identified as Bacillus pumilus, with the capability to produce cholesterol oxidase enzyme (55 kDa). The production of the enzyme was optimized via two-step statistical approach. Out of eight factors screened in Plackett–Burman, only four had significant effects on enzyme activity. The optimization process of these four variables by Box–Behnken revealed that the maximum enzyme activity (90 U/mL) was significantly obtained after 6 days of fermentation with 0.3%, 1% and 0.2% of NH4NO3, yeast extract and Tween 80, respectively. The purified enzyme showed optimum activity at pH 7.5 and temperature of 40 °C. The enzyme retained 100% of its activity after storage at 40 °C for 60 min. The enzyme also exhibited enhanced stability in the presence of Tween 80, methanol and isopropanol. This solvent and thermal stress tolerant enzyme, produced by B. pumilus, may provide a practical option for industrial and analytical applications.