Kombucha is a slightly alcoholic beverage produced using sugared tea via fermentation using the symbiotic culture of bacteria and yeast (SCOBY). This study aimed to optimize the production of soursop kombucha and determine the effects of different storage conditions on the quality, metabolites, and biological activity. The response surface method (RSM) results demonstrated that the optimum production parameters were 300 ml soursop juice, 700 ml black tea, and 150 g sugar and 14 days fermentation at 28°C. The storage conditions showed significant (P < 0.05) effects on the antioxidant activity including the highest antioxidant activity for the sample stored for 14 days at 25°C in light and the highest total phenolic content (TPC) for the sample stored for 7 days at 4°C in the dark. No significant effects were observed on the antimicrobial activity of soursop kombucha toward Escherichia coli and Staphylococcus aureus. The microbial population was reduced from the average of 106 CFU/ml before the storage to 104 CFU/ml after the storage at 4 and 25°C in dark and light conditions. The metabolites profiling demonstrated significant decline for the sucrose, acetic acid, gluconic acid, and ethanol, while glucose was significantly increased. The storage conditions for 21 days at 25°C in the dark reduced 98% of ethanol content. The novel findings of this study revealed that prolonged storage conditions have high potential to improve the quality, metabolites content, biological activity, and the Halal status of soursop kombucha.

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A layer of zinc oxide was synthesized on a zinc substrate using the Zn-air system in which the zinc substrate was used as the anode, air-cathode as a cathode, and a low concentration of potassium hydroxide was used to mediate the electrodes. In this study, the effects of the discharge current and ambient temperature were studied. The synthesis profile shows faster synthesis at higher drainage currents and at higher ambient temperatures. The X-ray diffraction pattern reveals that the zinc peak only appears after 20 mA and at 40°C, while the ZnO peak increases with discharge currents up to 50 mA and 80°C and decreases at higher discharge currents and temperatures. Morphology studies show that with elevated discharge currents, the ZnO arrays were downgraded and at elevated ambient temperatures, the size of the ZnO structures become larger; thus, both scenarios lead to a lower surface-to-volume ratio structures of the ZnO arrays. Transmission electron microscopy images show needle-like structures with a width of ϳ20 nm at the pointed end. Finally, photoluminescence spectroscopy readings suggest that synthesized ZnO possesses a bandgap energy ͑E g ͒ of 3.26 eV and drops in the ultraviolet region.A zinc-air ͑Zn-air͒ system consists of a zinc ͑Zn͒ foil anode, an electrolyte, normally potassium hydroxide ͑KOH͒, and an aircathode. The air-cathode absorbs and reduces oxygen from the ambient air into hydroxyl ͑OH − ͒ ions that react with released anodic Zn ions ͑Zn 2+ ͒ to form zinc oxide ͑ZnO͒. Supporting work by Mohamad 1 shows that ZnO was formed on the Zn anode and identifies the oxide formation as the cause of the Zn-air system failure. Equation 1-4 give the overall chemical equation of the ZnO formation process via the Zn-air system.At the air cathodeAt the Zn anodeZnO, a II-VI semiconductor with a direct wide bandgap of 3.37 eV and a relatively large free excitation binding energy of 60 meV at room temperature, is one of the most promising materials for the fabrication of optoelectronic devices operating in the blue and ultraviolet ͑UV͒ region and for gas sensing applications. 2 ZnO is an inexpensive n-type semiconductor that crystallizes in a hexagonal wurzite structure with a lattice spacing of c = 5.205 Å and a = 3.249 Å. It is a unique material that exhibits semiconducting, piezoelectric, and pyroelectric multiple properties. 3 It has drawn increasing attention because of its electrical conductivity, optical transparency, and piezoactivity, 4 giving it applications in electrophoto-mechanical nanodevices and photovoltaic cells. 5 Even though the ZnO wurtzite structure has already been applied in many devices, developing fabrication methods to produce better-oriented ZnO at lower costs has been a continued goal.Current ZnO synthesis technique such as the anodization technique 6 is one of the most versatile surface treatments to produce oxide films. In most anodization studies, its preparations require additional apparatus such as expensive reference electrode, deaeration, or agitation system and even the need of a ...

The effect of a gel polymer electrolyte (GPE) as the redox electrolyte used in dye-sensitized solar cells was studied. A GPE solution consisting of 0.5 M sodium iodide, 0.05 M iodine, and ethylene carbonate/propylene carbonate (1:1 w/w) binary solvents was mixed with increasing amounts of styrene-acrylonitrile (SAN). Bulk conductivity measurements show a decreasing trend from 4.54 to 0.83×10 −3 S cm −1 with increasing SAN content. The GPE exhibits Newtonian-like behavior and its viscosity increases from 0.041 to 1.093 Pa s with increasing SAN content. A balance between conductivity (1.3×10 −3 S cm −1 ) and viscosity (1.4 Pa s) is observed at 19 wt.% SAN. Fourier transform infrared spectroscopy detects elevated ring torsion at 706 cm −1 upon the addition of SAN into the liquid electrolyte. This indicates that SAN does not bond with the liquid electrolyte. Finally, the potential stability window of 19 wt.% SAN, which ranges from −1.68 to 1.38 V, proves its applicability in solar cells.