Photofermentative hydrogen production from volatile fatty acids present in dark fermentation effluents

In the present study, the growth and hydrogen production of Rhodobacter sphaeroides O.U. 001, was investigated in media containing five different volatile fatty acids (VFA) individually (malate, acetate, propionate, butyrate and lactate) and in media containing mixtures of these acids that reflect the composition of dark fermentation effluents. The highest hydrogen production rate was obtained in malate (24 ml_hydrogen/l_reactor h) and the highest biomass concentration was obtained in acetate containing media (1.65 g/l). The substrate conversion efficiencies for different volatile fatty acids were found to vary between 14 and 50%. The malate and butyrate consumption rates were first order with consumption rate constants of 0.026 h⁻¹ and 0.015 h⁻¹, respectively. In the case of substrate mixtures, it was observed that the bacteria consumed acetate first, followed by propionate and then butyrate. It was also found that the consumption rate of the main substrate significantly increased when the minor substrates were depleted.     

A computational and experimental approach to develop minocycline-imprinted hydrogels and determination of their drug delivery performances

In this study, minocycline-imprinted hydrogels are developed for controlled drug delivery in ocular disease treatments. An integrated computational and experimental study are conducted for investigating the relationship between design parameters and the drug loading/release performance of hydrogels. First, suitable functional monomers are determined for successful drug-imprinting by studying pre-polymerization conditions with full-atom molecular dynamics (MD) simulations. MD simulations suggest that acrylic acid and itaconic acid are suitable monomers for imprinting minocycline. Then, minocycline-imprinted hydrogels are synthesized with acrylic acid, commonly used in hydrogels, and three different amounts of cross-linker ethylene glycol dimethacrylate, 1, 2 and 3 mol%. All hydrogels are characterized and their drug loading and release performances are determined. Our computational and experimental calculations indicate an optimum cross-linker amount of 2 mol% for controlled minocycline release from imprinted hydrogels with an imprinting factor of almost 3. Finally, the drug release kinetics are determined by Korsmeyer-Peppas model.     

Photofermentative hydrogen production using dark fermentation effluent of sugar beet thick juice in outdoor conditions

In the present study, photofermentative hydrogen production on thermophilic dark fermentation effluent (DFE) of sugar beet thick juice was investigated in a solar fed-batch panel photobioreactor (PBR) using Rhodobacter capsulatus YO3 (hup⁻) during summer 2009 in Ankara, Turkey. The DFE was obtained by continuous dark fermentation of sugar beet thick juice by extreme thermophile Caldicellulosiruptor saccharolyticus and it contains acetate (125 mM) and NH₄⁺ (7.7 mM) as the main carbon and nitrogen sources, respectively. The photofermentation process was done in a 4 L plexiglas panel PBR which was daily fed at a rate of 10% of the PBR volume. The DFE was diluted 3 times to adjust the acetate concentration to approximately 40 mM and supplemented with potassium phosphate buffer, Fe and Mo. In order to control the temperature, cooling was provided by recirculating chilled water through a tubing inside the reactor. Hydrogen productivity of 1.12 mmol/L_c/h and molar yield of 77% of theoretical maximum over consumed substrate were attained over 15 days of operation. The results indicated that Rb. capsulatus YO3 could effectively utilize the DFE of sugar beet thick juice for growth and hydrogen production, therefore facilitating the integration of the dark and photo-fermentation processes for sustainable biohydrogen production.     

Experimental research and use of finite elements method on mechanical behaviors of honeycomb structures assembled with epoxy-based adhesives reinforced with nanoparticles

This study utilized experimental and finite element methods to investigate the mechanical behavior of aluminum honeycomb structures under compression. Aluminum honeycomb composite structures were subjected to pressing experiments according to the standard ASTM C365. Resistive forces in response to compression and maximum compressive force values were measured. Structural damage was observed. In the honeycomb structure, the cell width decreased as the compressive force increased. Results obtained with finite element models generated using ANSYS Workbench 15 were validated. Experimental results paralleled the finite element modeling results. The ANSYS results were approximately 85 % reliable.     

Effect of biopolymers containing natamycin against Aspergillus niger and Penicillium roquefortii on fresh kashar cheese

Fungal spoilage during refrigerated storage is one of the main safety and quality‐related problems for dairy products. The effect of wheat gluten (WG) and methyl cellulose (MC) biopolymers containing natamycin (NA) on the growth of Aspergillus niger and Penicillium roquefortii on the surface of fresh kashar cheese during storage at 10 °C for 30 days was investigated. Wrapping of A. niger‐inoculated cheese with MC films containing 5–20 mg NA per 10 g resulted in approximately 2‐log reductions in spore count. Two mg NA per 10 g included into WG films was sufficient to eliminate A. niger on the surface of cheese. However, MC and WG films containing NA did not cause any significant decrease in P. roquefortii count on the cheese surface. Therefore, especially use WG films in dairy applications could be an effective way of controlling A. niger growth on these products.     

A Single-Step Process for Direct Reduction of Iron Oxide to Sponge Iron by Undiluted Methane

A single-step pyrometallurgical process for the synthesis of sponge iron is presented in this study. It aimed to investigate the reduction behavior of Fe₂O₃ in undiluted CH₄ flow to establish the process parameters for sponge Fe formation. Thermodynamic analysis predicted the reduction of Fe₂O₃ to Fe by CH₄ at 1000–1200 K. The experiments were carried out at 800–1200 K for 60 min and at 1200 K for 0–60 min. Mass measurement and x-ray diffraction (XRD), and scanning electron microscope techniques were used to characterize the products. The extent of the oxide reduction was found to increase with the temperature and time. XRD showed that single phase Fe was obtained at 1100 K for 60 min and at 1200 K within 10 min. The products synthesized at 1200 K within 15 min had spongy morphology. C deposition on the pre-reduced Fe particles resulted in the disappearance of spongy character.     

Applications of natural zeolites on agriculture and food production

Zeolites are crystalline hydrated aluminosilicates with remarkable physical and chemical properties, which include losing and receiving water in a reverse way, adsorbing molecules that act as molecular sieves, and replacing their constituent cations without structural change. The commercial production of natural zeolites has accelerated during the last 50 years. The Structure Commission of the International Zeolite Association recorded more than 200 zeolites, which currently include more than 40 naturally occurring zeolites. Recent findings have supported their role in stored‐pest management as inert dust applications, pesticide and fertilizer carriers, soil amendments, animal feed additives, mycotoxin binders and food packaging materials. There are many advantages of inert dust application, including low cost, non‐neurotoxic action, low mammalian toxicity and safety for human consumption. The latest consumer trends and government protocols have shifted toward organic origin materials to replace synthetic chemical products. In the present review, we summarize most of the main uses of zeolites in food and agruculture, along with the with specific paradigms that illustrate their important role. © 2017 Society of Chemical Industry     

Significance of carbon to nitrogen ratio on the long-term stability of continuous photofermentative hydrogen production

The stable and optimized operation of photobioreactors (PBRs) is the most challenging task in photofermentative biological hydrogen production. The carbon to nitrogen ratio (C/N) in the feed is a critical parameter that significantly influences microbial growth and hydrogen production. In this study, the effects of changing the C/N ratio to achieve stable biomass and continuous hydrogen production using fed-batch cultures of Rhodobacter capsulatus YO3 (uptake hydrogenase deleted, hup-) were investigated. The experiments were carried out in 8 L panel PBRs operated in indoor conditions under continuous illumination and controlled temperature. Culture media containing different acetate (40-80 mM) and glutamate (2-4 mM) concentrations were used to study the effects of changing the C/N ratio on biomass growth and hydrogen production. Stable biomass concentration of 0.40 g dry cell weight per liter culture (gDCW/L_c) and maximum hydrogen productivity of 0.66 mmol hydrogen per liter culture per hour (mmol/L_c/h) were achieved during fed-batch operation with media containing 40 mM acetate and 4 mM glutamate, C/N = 25, for a period of over 20 days. A study on the effect of biomass recycling on biomass growth and hydrogen production showed that the feedback of cells into the photobioreactor improved biomass stability during the fed-batch operation but decreased hydrogen productivity.     

Nanomaterial processing strategies in functional hybrid materials for wastewater treatment using algal biomass

Algal cultivation has tremendous potential in wastewater treatment, and its simultaneous biomass production has advantages for the production of value added products such as biodiesel, fertilizers and pharmaceuticals. Some obstacles to obtaining a productive biological water treatment and bioenergy system are the harvesting and processing of biomass. Such issues can be addressed using nano‐bio hybridization approaches by simplifying the microbial harvesting step along with increasing the efficiency of wastewater treatment. This review highlights studies within our research group that are based on the fabrication of functional hybrid materials using algal biomass, including: (i) electrospun nanofibers; (ii) laminar nanomaterials; and (iii) magnetic nanoparticles impregnated in a polymer. All of these techniques have been used for the removal of waste pollutants such as nitrate and phosphate ions. The multidisciplinary techniques have potential to provide effective algal culture systems for industrial applications, while having a significant impact on wastewater treatment. © 2017 Society of Chemical Industry