Effects of aliphatic acids, furfural, and phenolic compounds on Debaryomyces hansenii CCMI 941

Debaryomyces hansenii is a polyol overproducing yeast that can have a potential use for upgrading lignocellulosic hydrolysates. Therefore, the establishment of its tolerance to metabolic inhibitors found in hydrolysates is of major interest. We studied the effects of selected aliphatic acids, phenolic compounds, and furfural. Acetic acid favored biomass production for concentrations <6.0 g/L. Formic acid was more toxic than acetic acid and induced xylitol accumulation (maximum yield of 0.21 g/g of xylose). All tested phenolics strongly decreased the specific growth rate. Increased toxicity was found for hydroquinone, syringaldehyde, and 4-methylcatechol and was correlated to the compound’s hydrophobicity. Increasing the amount of furfural led to longer lag phases and had a detrimental effect on specific growth rate and biomass productivity.     

The combined effects of acetic acid, formic acid, and hydroquinone on Debaryomyces hansenii physiology

The combined effects of inhibitors present in lignocellulosic hydrolysates was studied using a multivariate statistical approach. Acetic acid (0–6 g/L), formic acid (0–4.6 g/L) and hydroquinone (0–3 g/L) were tested as model inhibitors in synthetic media containing a mixture of glucose, xylose, and arabinose simulating concentrated hemicellulosic hydrolysates. Inhibitors were consumed sequentially (acetic acid, formic acid, and hydroquinone), alongside to the monosaccharides (glucose, xylose, and arabinose). Xylitol was always the main metabolic product. Additionally, glycerol, ethanol, and arabitol were also obtained. The inhibitory action of acetic acid on growth, on glucose consumption and on all product formation rates was found to be significant (p≤0.05), as well as formic acid inhibition on xylose consumption and biomass production. Hydroquinone negatively affected biomass productivity and yield, but it significantly increased xylose consumption and xylitol productivity. Hydroquinone interactions, either with acetic or formic acid or with both, are also statistically signficant. Hydroquinone seems to partially lessen the acetic acid and amplify formic acid effects. The results clearly indicate that the interaction effects play an important role on the xylitol bioprocess.     

Novel Antiretroviral Therapeutic Strategies for HIV

When the first cases of HIV infection appeared in the 1980s, AIDS was a deadly disease without any therapeutic alternatives. Currently, there is still no cure for most cases mainly due to the multiple tissues that act as a reservoir for this virus besides the high viral mutagenesis that leads to an antiretroviral drug resistance. Throughout the years, multiple drugs with specific mechanisms of action on distinct targets have been approved. In this review, the most recent phase III clinical studies and other research therapies as advanced antiretroviral nanodelivery systems will be here discussed. Although the combined antiretroviral therapy is effective in reducing viral loading to undetectable levels, it also presents some disadvantages, such as usual side effects, high frequency of administration, and the possibility of drug resistance. Therefore, several new drugs, delivery systems, and vaccines have been tested in pre-clinical and clinical trials. Regarding drug delivery, an attempt to change the route of administration of some conventional antiretrovirals has proven to be successful and surpassed some issues related to patient compliance. Nanotechnology has brought a new approach to overcoming certain obstacles of formulation design including drug solubility and biodistribution. Overall, the encapsulation of antiretroviral drugs into nanosystems has shown improved drug release and pharmacokinetic profile.     

Interactions of Omeprazole and Precursors with beta-Cyclodextrin Host Molecules

β-Cyclodextrin (β-CD) was mixed with omeprazoleand some of its precursors in aqueous or water/ethanol solutions, and theresulting crystalline products have been characterized by elemental analysis,thermogravimetry, powder X-ray diffraction (XRD), FTIR and ¹³C CP MAS NMRspectroscopy. In the case of2-chloromethyl-4-methoxy-3,5-dimethylpyridine...HCl, itwas found that the solid product always consisted of pure β-CD hydrate. On the other hand, a 2 : 1(host-to-guest) inclusion complex was obtained between β-CD and2-methoxy-2-mercaptobenzimidazole. The thioether intermediate5-methoxy-2-[(3,5-dimethyl-4-methoxy-2-pyridine)methylthio]-1H-benzimidazoleand its sulfoxide derivative (omeprazole) both formed 1 : 1 inclusion complexes with β-CD. Powder XRD indicates that the crystal packing of β-CDhost molecules is herringbone-type for the 2 : 1 complex, and channel-typefor the 1 : 1 complexes. Ab initio calculations were carried out toinvestigate thehost–guest interactions. It was found that the interactionwith the pyridine fragment is wholly repulsive, due to the presence of severalring substituents. On the other hand, the inclusion of the benzimidazole fragmentis energetically favored, but highly dependent on the orientation of thesubstituent methoxy group.     

Optimization of Brewery's spent grain dilute-acid hydrolysis for the production of pentose-rich culture media

Dilute-acid hydrolysis of brewery's spent grain to obtain a pentose-rich fermentable hydrolysate was investigated. The influence of operational conditions on polysaccharide hydrolysis was assessed by the combined severity parameter (CS) in the range of 1.39–3.06. When the CS increased, the pentose sugars concentration increased to a maximum at a CS of 1.94, whereas the maximum glucose concentration was obtained for a CS of 2.65. The concentrations of furfural, hydroxymethylfurfural (HMF), as well as formic and levulinic acids and total phenolic compounds increased with severity. Optimum hydrolysis conditions were found at a CS of 1.94 with >95% of feedstock pentose sugars recovered in the monomeric form, together with a low content of furfural, HMF, acetic and formic acids, and total phenolic compounds. This hydrolysate containing glucose, xylose, and arabinose (ratio 10∶67∶32) was further supplemented with inorganic salts and vitamins and readily fermented by the yeast Debaryomyces hansenii CCMI 941 without any previous detoxification stage. The yeast was able to consume all sugars furfural, HMF, and acetic acid with high biomass yield, 0.68C-mol/C-mol, and productivity, 0.92 g/(L·h). Detoxification with activated charcoal resulted in a similar biomass yield and a slight increase in the volumetric productivity (11%).     

Ultrasound Speeds and Molar Isentropic Compressions of Aqueous Binary Mixtures of Diethylamine from 278.15 to 308.15 K

Ultrasound speeds in aqueous binary mixtures of diethylamine (DEA) were measured across the entire composition range at five temperatures between 278.15 and 308.15 K. Isentropic compressibilities, κ _S , were calculated from the ultrasound speed and density data. The excess molar isentropic compressions, K _S,m ^E, were estimated and their variation with the mole fraction of the amine were fitted by the Redlich–Kister equation. Excess partial molar isentropic compressions, K _S,i ^E, were then obtained, allowing separation of the role of each component in the mixing process. Interesting insights are gained from the analysis of the temperature and composition dependence of K _S,i ^E, principally in the water-rich region. A comparison of the limiting values of this property with those of the limiting excess partial molar isobaric expansion, E _P,i ^E,∞, previously published, clearly shows the different sensitivity of these two differential thermodynamic properties to the mixing process. The different behavior of the temperature dependence of K _S,i ^E,∞ in the systems, water + DEA, and water + 2-diethylaminoethanol (DEEA), are also analyzed and interpreted in terms of changes in the solute configuration, the degree of hydrolysis and solute-solvent interactions.     

Can the HVL help the mechanical X‐ray tube characterization?

High‐intensity X‐ray beams are usually characterized by their kVp (kilovoltage peak) value and half‐value layer (HVL). While the first parameter is reasonably well known (apart from accelerating potential fluctuations), on the second, there is a greater deal of uncertainty. The HVL depends on the used filtration, the effective kVp value and on some of the X‐ray tube mechanical features, such as the anode angle. This last parameter is not always provided by the tube manufacturer, so we may question if the HVL dependence on the anode angle can be used to extract information on this angle. We tried to give an answer to this question using two different numerical models and a full Monte Carlo (MC) program to simulate the photon field produced by the X‐ray tube for several anode angles. One of the numerical models was developed by the Institute of Physics and Engineering in Medicine and gives X‐ray spectra and HVL values for a wide range of kVp values and anode angles. The other model, named SpekCalc, is based on a theoretical work developed by Gavin Poludniowski and Phil Evans. The MC simulation was done using the PENELOPE code for coupled electron‐photon transport. Using the computed photon spectra, HVLs were obtained and compared with experimental HVL values obtained with a Philips PW 2184/00 X‐ray tube with a 26° tungsten anode and accelerating potentials in the range of 40–90 kVp. We are now able to show the PENELOPE simulation can deliver the correct anode angle value. Copyright © 2011 John Wiley & Sons, Ltd.     

Dilute Acid Hydrolysis of Wheat Straw Oligosaccharides

The dilute acid posthydrolysis of wheat straw hemicellulosic oligosaccharides obtained by autohydrolysis was evaluated. An empirical model was used to describe the effect of catalyst concentration (sulfuric acid, 0.1–4% w/w) and reaction time (0–60 min) based on data from a Doehlert experimental design. Catalyst concentration is the main variable influencing posthydrolysis performance, as both its linear and quadratic coefficients are statistically significant for the majority of the studied variables, namely, the ones related to sugar and byproducts production. Reaction time influences xylose and furan derivatives concentrations but not phenolics or acetic acid content. Catalyst concentration and reaction time interact synergistically, minimizing sugar recovery and promoting furan derivatives production. Based on the proposed models, it was possible to delimit an operational range that enables to obtain high monosaccharides recovery together with a slight decrease in inhibitors content as compared to the standard acid hydrolysis treatment. Furthermore, this is achieved with up to 70% less acid spending or considerable savings on reaction time.     

Comparison of two posthydrolysis processes of Brewery's spent grain autohydrolysis liquor to produce a pentose-containing culture medium

A readily fermentable pentose-containing hydrolysate was obtained from Brewery's spent grain by a two-step process consisting of an auto-hydrolysis (converting the hemicelluloses into oligosaccharides) followed by an enzymatic or sulfuric acid-catalyzed posthydrolysis (converting the oligosaccharides into monosaccharides). Enzymatic hydrolyses were performed with several commercial enzymes with xylanolytic and cellulolytic activities. Acid-catalyzed hydrolyses were carried out at 121°C under various sulfuric acid concentrations and reaction times, and the effects of treatments were interpreted by means of a corrected combined severity factor (CS ¹), which varied in the range of 0.80–2.01. Under the tested conditions, chemicalhydrolysis allowed higher pentose yields than enzymatic hydrolysis. Optimized conditions (defined by CS ¹=1.10) allowed both complete monosaccharide recovery and low content of inhibitors. Liquors subjected to posthydrolysis under optimal conditions were easily fermented by Debaryomyces hansenii CCMI 941 in semiaerobic shake-flask experiments, leading to xylitol and arabitol as major fermentation products. The bioconversion process was improved by hydrolysate concentration and supplementation of fermentation media with casamino acids. The authors wish it to be known that the first two authors should be regarded as joint First Authors.