Volume 70, Issue 7

The amount of citric acid (CA) produced by Yarrowia lipolytica is dependent on the yeast strain and growth conditions such as pH, oxygen availability and medium composition. In this work, an experimental design based on the Taguchi method was applied to evaluate the effect of parameters: pH, carbon/nitrogen (C/N) ratio in the medium, oxygen mass transfer rate (OTR) and salts concentration, on the CA production by two Y. lipolytica strains , W29 (ATCC 20460) and CBS 2073. OTR and pH showed higher influence on the CA production for both strains. The increase of OTR from air to the culture medium led to a two- and three-fold improvement of the CA production by Y. lipolytica CBS 2073 and W29, respectively. Besides the individual effects of the parameters, a significant influence of the interaction between these parameters was observed, mainly between OTR and salts. Different values of the parameters were found at the optimum conditions for each strain, but the theoretically predicted and experimentally obtained citric acid concentrations (c CA ) were approximately 10 g L -1 for both strains. The optimal conditions were also validated employing crude glycerol from biodiesel industry as a substrate, and similar behaviour of the strains was observed.

Physico–chemical models of the interactions of cells with solid surfaces, which use contact angles and zeta potentials, indicated more facile adsorption of cells of Pseudomonas putida TVA8 on the quartz surface after its treatment with 3-aminopropyltriethoxysilane (APTES). A whole-cell optical fibre sensor of toluene was prepared by the adsorption of P. putida TVA8, bacteria producing light in contact with toluene on the wider end of APTES-treated quartz tapered optical fibre. The results of the measurements of luminescence from both sides of the layer of adsorbed cells were compared. Over the 135 days trial, the fibre biosensor was repetitively induced with toluene solution (26.5 mg L −1 ) 68 times. The intensities of bioluminescence gradually decreased due to release of the adsorbed cells and they were only temporarily restored by the addition of nutrients. The intensities of bioluminescence induced with contaminated ground water were lower than in the mineral medium (MSM) with the same content of toluene.

N -hydroxyphthalimide (NHPI) combined with stable and recoverable transition metal–aluminium binary hydrotalcite-like compounds (M-Al HTLcs, M = Cu, Ni, Co) as an unprecedented catalytic system was demonstrated for the allylic carbonylation, as the model reaction, of cyclic olefins with tert-butyl hydroperoxide (TBHP), using isophorone (IP) to ketoisophorone (KIP). The results showed NHPI combined with Cu-Al HTLcs to be an efficient catalytic system and the influences of various reaction conditions of the catalytic reaction were optimised. A maximum IP conversion of 68.0 % with 81.8 % selectivity to KIP was afforded under the optimal reaction conditions. Experiments of repeatability and restorability showed Cu-Al HTLcs to be stable for at least five cycles without noticeable loss of catalytic activity. Expanding substrates could also be efficiently converted to the corresponding ketones under the optimised reaction conditions with appreciable yields. A plausible catalytic reaction mechanism was proposed.

The effect of platinum loading (0.09–1.00 mass %) on the performance of ceria–zirconia supported catalysts in the total oxidation of ethanol and toluene in air was investigated. The introduction of platinum promoted the reduction of surface cerium and decreased the acidity of the catalysts. In ethanol oxidation, the temperature of 50 % conversion decreased with increasing platinum content. This increase in catalytic performance was more pronounced for the catalysts with 0.59 mass % and 1.00 mass % Pt. On the other hand, higher amount of by-products (mainly acetaldehyde) was observed at increased platinum loadings. For all catalysts, a correlation between their H 2 -TPR profiles and catalytic performance was revealed. In toluene oxidation, only the catalysts with 0.59 mass % and 1.00 mass % Pt exhibited a lower temperature of 50 % conversion than pristine ceria–zirconia. The effect of platinum loading was less pronounced than in ethanol oxidation and a correlation between reduction behaviour and catalytic performance was not observed. The superior catalytic performance of the catalysts with 0.59 mass % and 1.00 mass % of Pt in both ethanol and toluene oxidation was ascribed to the presence of large platinum nanoparticles, which were not observed at lower Pt loadings.

4-amino-2-iminodithiole derivatives were synthesised via multi-component reactions of tetramethyl thiourea, isothiocyanates and alkyl bromides in the presence of ZnO nanorods (ZnO-NR) as the catalyst in water at ambient temperature. These reactions provide low yields without catalysts. The catalyst exhibited significant reusable activity.

In this study, a novel flat-type synergic-supported liquid membrane was evaluated with a mixture of N -methyl- N,N,N -trioctylammonium chloride (Aliquat 336) and tributyl phosphate (TBP) as the carrier and kerosene as the diluent to remove Cr(VI) from synthetic waste water. The main parameters involved in the process were identified and optimised. The parameters were divided into two groups, those that were independent and those having an interaction. The parameters of the carrier/kerosene volumetric proportion and stirring rate were optimised individually due to their nature. The optimal values of these parameters were 0.5 and 500 min −1 , respectively, for a constant carrier/kerosene ratio and stirring rate in the designed experiments using the response surface method (RSM). The four parameters of TBP/Aliquat 336, chromium concentration in the feed phase, feed and product pH were optimised using RSM; it was observed that the TBP/Aliquat 336 ratio, feed pH, pH of the stripping phase and interaction of this parameter with feed concentration have the most important effects on the removal of Cr(VI). The optimal levels of these parameters were 0.61, 71.75 mg L −1 , 3.5 and 12.66 for the ratio of TBP/Aliquat 336, feed chromium concentration, pH of the feed and pH of the product, respectively. An experimental removal rate of 94.63 % at the optimized levels was obtained.

Experimental study on PVC-based materials (PVC = poly (vinyl chloride)) pyrolysis; in the presence of various amounts of steelmaking dust was performed. Dust from steel manufacture employing zinc plated scrap contains a considerable amount of zinc oxide (ZnO) and its utilization in metallurgy is quite complicated. However, the dust can react with hydrogen chloride (HCl) released from heated PVC in the temperature range of 200–400°C. Material balance of the pyrolysis process was studied by thermogravimetry, and the data obtained were compared with the results of larger laboratory oven experiments. In excess of PVC, the amount of captured HCl stoichiometrically corresponds to the content of ZnO; additional HCl is probably captured by FeCl 2 , while FeCl 3 is not formed at elevated temperatures. In excess of the dust, the captured amount of HCl is approximately 100 %. The suggested co-pyrolysis seems to be a promising method to prevent the formation of dangerous chlorinated organic compounds during the thermal treatment of waste PVC. Furthermore, the obtained ZnCl 2 is a valuable material and the zinc depleted dust can be reused in metallurgy instead of its disposal.

Ti-pillared bentonites (Ti-PBs) were synthesised using bentonite from the Hançılı region in Turkey. Ti(IV) chloride, Ti(IV) ethoxide and Ti(IV) propoxide were used as the titanium sources; the syntheses were carried out using different H + /Ti ratios, bentonite suspension percentages and calcination temperatures. Titanium was found in the form of titanium dioxide for all the sources. The Ti(IV) chloride source afforded a sample with a significantly higher specific BET surface area (by 323 m 2 g −1 ), TiO 2 content of 50.5 mass % and a more microporous structure with a micropore volume of 0.112 cm 3 g −1 ; the Ti(IV) propoxide source afforded a more mesoporous structure with a higher total pore volume. The micropore region showed the formation of pores of different sizes, while prominent narrow peaks were obtained in the mesopore region. Ti-PBs, which exhibited only the anatase phase of titanium dioxide, yielded high Bronsted and Lewis acidities. When the rutile phase and the anatase phase occurred together, as a result of the lower TiO 2 content, the Bronsted and Lewis acidities of the Ti-PBs decreased. The use of Ti(IV) chloride and Ti(IV) propoxide sources at H + /Ti ratios of 4.0 and a bentonite suspension percentage of 2.0 resulted in samples exhibiting strong Brønsted acidity.

There are large numbers of paper cultural relics in China, the country where paper making was invented. However, the paper relics have not been adequately protected so they are at risk of ageing, damage and disappearance. In order to better protect the paper relics, modified carboxymethyl cellulose/Si/polyacrylate protective materials were prepared with acrylicresin and modified carboxymethyl cellulose which has a good affinity with the paper and modified silica, improving the mechanical strength and ability to withstand weathering. The modified CMC/Si/polyacrylate protective material was analysed using infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry and other performance-testing devices. The surface morphology of the paper samples was analysed using scanning electron microscopy. The protective material so prepared was evaluated by subjection to accelerated ageing (dry heat treatment). The results showed the protective material films to have good hydrophobicity, acid/alkali resistance and mechanical strength. When the content of SiO 2 is 6 mass %, the protective material has an excellent comprehensive performance. The results of the ageing test reveal that the prepared material can effectively slow down the ageing rate. The prepared material is suited to the protection of paper cultural relics.

Mixed matrix materials, containing poly(dimethylsiloxane), phosphine oxide-based polyimide, and zeolite Y were prepared by means of blending hybridisation. The thermal stability of the materials and the hydrophobic properties were enhanced. The decrease in the glass transition temperature of the materials with the increase in poly(dimethylsiloxane) content supported the polymer-chain flexibility. The pristine polyimide and the zeolite-filled polyimide exhibited the highest transparency. Fourier transform infrared (FTIR) spectroscopy confirmed that the increase in the amount of the lowest molecular mass poly(dimethylsiloxane) ingredient indicated strong alkyl and Si—O—Si stretching modes, whilst the alkyl and Si—O—Si stretching intensity decreased in the presence of the highest amount of and the highest molecular mass poly(dimethylsiloxane). The hydrophobic poly(dimethylsiloxane) moiety created an inverse relationship between the porosity of the materials (surface roughness) and the hydrophilicity. The nanocrystallite domain, identified by X-ray diffraction analysis (XRD) and possessing an exotherm crystallisation peak, occurred in the lowest amount of poly(dimethylsiloxane) with the highest molecular mass-based hybrid material. The nanocrystallite enhanced the storage modulus as determined by the dynamic mechanical analyser (DMA). The nanocrystalline formation resulted in a slight increase in the alkyl stretching and the Si—O—Si stretching of the lowest amount of and the highest molecular mass poly(dimethylsiloxane)-containing material over those of the lowest molecular mass poly(dimethylsiloxane) in the same amounts of material involved.

Syntheses of new N -demethyl- N -substituted analogues (propyl, allyl) of 1-fluorocodeine and their 7,8-dihydro derivatives were described starting from codeine. 1-Fluoronorcodeine and 1-fluorodihydronorcodeine were prepared by N -demethylation with α -chloroethyl chloroformate from the corresponding 6- O -acetyl protected derivatives. 3- O -Demethylation of 1-fluorocodeine and 1-fluorodihydrocodeine with boron tribromide resulted in 1-fluoromorphine and 1-fluorodihydromorphine respectively. 1-Fluorodihydromorphine was acetylated to 3,6-di- O -acetyl-1-fluorodihydromorphine. 8-Fluoroapocodeine and N -propyl-8-fluoroapocodeine were synthesized from the appropriate 1-fluorocodeine derivatives by acid-catalyzed rearrangement.

A series of novel quinazolinone derivatives containing a 1,2,4-triazolylthioether moiety were synthesised and their antimicrobial activities were evaluated. All the target compounds were characterised by 1 H NMR, 13 C NMR, ESI-MS, IR and elemental analyses. The single crystal structure of 3-((5-((2-fluorobenzyl)thio)-4-phenyl-4 H -1,2,4-triazol-3-yl)methyl)quinazolin-4(3 H )-one ( VIIi ) was also determined. The preliminary bioassays indicated that some of the target compounds possessed good antimicrobial activities. For example, 3-((4-phenyl-5-((4-(trifluoromethyl)benzyl)thio)-4H-1,2,4-triazol-3-yl)methyl)quinazolin-4(3 H )-one ( VIIs ) exhibited the best inhibitory effect against Xanthomonas oryzae pv. oryzae and Xanthomonas axonopodis pv. citri with the half-effective concentration (EC 50 ) values of 47.6 μg mL −1 and 22.1 μg mL −1 , respectively, which were superior to the commercial bactericide, bismerthiazol. Meanwhile, 3-((5-((4-chlorobenzyl)thio)-4-phenyl-4H-1,2,4-triazol-3-yl)methyl)quinazolin-4(3 H )-one ( VIIh ) exhibited better fungicidal activities against Pellicularia sasakii and Colletotrichum capsici at the concentration of 50 μg mL −1 , in comparison with the commercial fungicide, hymexazol.

In the present study, the role of inter-residue interactions in ligand binding and the ligand-receptor interactions were examined. Computational chemistry methods of ligand docking and molecular dynamics simulations were used to study the binding of β -funaltrexamine ( β -FNA) and N-methyl- β -funaltrexamine (N-methyl- β -FNA) to μ- and κ -opioid receptors and to the μ-receptor with Lys303 6.58 Glu mutation. It was found that inter-residue interactions Lys233 5.39 -Glu303 6.58 in the mutant receptor and Lys227 5.39 -Asp223 5.35 in the κ-receptor are more likely to prevent covalent bond formation between β -FNA and the receptor than the ligand-receptor interactions. This emphasizes the importance of inter-residue interactions in ligand binding as well as the effects of point-mutations.