Efficient Extraction of Fermentation Inhibitors by Means of Green Hydrophobic Deep Eutectic Solvents

The methods for hydrogen yield efficiency improvements, the gaseous stream purification in gaseous biofuels generation, and the biomass pretreatment are considered as the main trends in research devoted to gaseous biofuel production. The environmental aspect related to the liquid stream purification arises. Moreover, the management of post-fermentation broth with the application of various biorefining techniques gains importance. Chemical compounds occurring in the exhausted liquid phase after biomass pretreatment and subsequent dark and photo fermentation processes are considered as value-added by products. The most valuable are furfural (FF), 5-hydroxymethylfurfural (HMF), and levulinic acid (LA). Enriching their solutions can be carried with the application of liquid–liquid extraction with the use of a suitable solvent. In these studies, hydrophobic deep eutectic solvents (DESs) were tested as extractants. The screening of 56 DESs was carried out using the Conductor-like Screening Model for Real Solvents (COSMO-RS). DESs which exposed the highest inhibitory effect on fermentation and negligible water solubility were prepared. The LA, FF, and HMF were analyzed using FT-IR and NMR spectroscopy. In addition, the basic physicochemical properties of DES were carefully studied. In the second part of the paper, deep eutectic solvents were used for the extraction of FF, LA, and HMF from post-fermentation broth (PFB). The main extraction parameters, i.e., temperature, pH, and DES: PFB volume ratio (V_DES:V_PFB), were optimized by means of a Box–Behnken design model. Two approaches have been proposed for extraction process. In the first approach, DES was used as a solvent. In the second, one of the DES components was added to the sample, and DES was generated in situ. To enhance the post-fermentation broth management, optimization of the parameters promoting HMF, FF, and LA extraction was carried under real conditions. Moreover, the antimicrobial effect of the extraction of FF, HMF, and LA was investigated to define the possibility of simultaneous separation of microbial parts and denatured peptides via precipitation.     

Physicochemical Characteristics of Biochar from Waste Cricket Chitin (Acheta domesticus)

The properties of biochar (BC) from crustacean chitin are relatively well understood, while there are few studies on BC from insect chitin. This study presents the characterization and phytotoxic assessment of BC produced from crickets and cricket chitin. Cricket powder (BCCR) and cricket chitin (BCCH) were pyrolyzed at 500 °C and 700 °C. Physicochemical characteristics, N ad-/desorption, FTIR, were examined. SEM images were also performed. Regardless of the pyrolysis temperature, biochars were characterized by a densely “packed” solid surface/monolithic type with a non-porous structure (0.05–0.22 m²/g) and high content of N (9.4–11.8%). BCCHs showed a higher pH (12.2–12.4) compared to BCCR (8.7–10.8). Based on the XRD analysis, BCs were characterized by an amorphous carbon turbostratic structure and a randomly oriented graphitic-like micro-crystallite structure. FTIR spectra of BCs confirmed the presence of various O₂ and N-functional groups on the BC surface. BCCHs added to soil at rates from 0.5 to 1.5% significantly reduced the germination of Lepidium sativum. Stimulation of root elongation was also observed in the case of BCCR500 1.0% and BCCR700 1.5%. Thermal degradation of cricket powder and cricket chitin promotes the formation of organic N-containing heterocyclic rings, which lead to the production of N-doped carbons with potential uses in energy storage and the contaminations sorption.     

Gramicidin A channel in a matrix from a semifluorinated surfactant monolayer

Gramicidin A, a polypeptide antibiotic forming transmembrane ion channels, has been incorporated into a Langmuir monolayer formed by a semifluorinated alkane (SFA). In this work, partially fluorinated tetracosane, perfluorohexyloctadecane (F6H18), has been applied, aiming at finding a suitable matrix for gramicidin A to be transferred onto solid support for a biosensor design. For this purpose, the physiological conditions were of special interest (mixed monolayers containing low gramicidin proportion and the surface pressure of 30 mN/m). Mixed monolayers of gramicidin and SFA were found to be miscible within the whole range of mole fractions. A very significant increase of the stability of SFA monolayer has been found in the presence of gramicidin, even at such a low proportion as X(gramicidin) = 0.1, which is reflected in a 3.5-fold increase of the collapse pressure value of mixed monolayer as compared to the film from pure SFA. This interesting phenomenon has been interpreted as being due to the existence of a strong dipole-dipole interaction between both film-forming molecules. Opposite sign of the measured electric surface potential for gramicidin and SFA, resulting from different directions of the dipole moment vectors in both film molecules, implies that the ordered, antiparallel orientation of the dipole moments in the mixed gramicidin/SFA system can be responsible for its extremely high stability.     

Adsorption of water vapour from humid air in carbon molecular sieves: carbosieve S-III and carboxens 569, 1000 and 1001

The adsorption of water vapour in carbon molecular sieves (CMS) used to determine volatile organic compounds (VOCs) in air was investigated. The CMS mass in the trap was found not to affect the mass of retained water under conditions of incomplete saturation of the adsorbent bed with water. Thus, the restrictions commonly imposed on the CMS mass are not necessary. The usefulness of four different CMSs to sample large volumes of humid air was estimated. Carboxen 1000 exhibited the best performance. To assess the magnitude of CMS mass in the trap in dependence on the volume, the relative humidity and the temperature of the sample, the use of a novel parameter, called the water vapour interference factor, was suggested.     

Synthesis of Some Quaternary N-(1,4-anhydro-5-deoxy-D,L-ribitol-5-yl)ammonium Salts

The successful removal of the isopropylidene-protecting group from 1,4-anhydro-2,3-O-isopropylidene-5-O-tosyl-D,L-ribitol and from quaternary N-(1,4-anhydro-5-deoxy-2,3-O-isopropylidene-D,L-ribitol-5-yl)ammonium salts is reported. The structures of all isolates were determined by spectral analysis, including extensive 2-D NMR analyses. Single-crystal x-ray diffractions of 1,4-anhydro-5-O-tosyl-D,L-ribitol and its 2,3-O-isopropylidene derivatives are reported.     

Swelling effects in cross-linked polymers by thermogravimetry

A Brazilian coal power plant generates a waste composed by the fly and bottom ashes produced from coal combustion and by a spent sulfated lime generated after SO₂ capture from combustion gases. This work presents a study of the early stages of the hydration of composites formed by this waste and a type II Portland cement, which will be used for CO₂ capture. The cement substitution degrees in the evaluated composites were 10, 20, 30 and 40%, and the effect of the coal power unit waste on the hydration reaction was analyzed on real time by NCDTA, during the first 40 h of hydration. The results show that the higher is the substitution degree, the higher is the retarding effect on the cement hydration process. Actually, by respective thermogravimetric (TG) and derivative thermogravimetric (DTG) analysis on initial cement mass basis, this effect is caused by double exchange reactions among Ca and Mg components of the waste, during the first 4 h of hydration, which promote a much higher exothermic effect in the NCDTA curve, simultaneously to respective induction periods. The pozzolanic reactions, due to the presence of the waste silica and alumina containing amorphous phases, consume part of the original Ca(OH)₂ content existent in the waste in the case of 30 and 40% substituted pastes, and also from part of the Ca(OH)₂ produced in cement hydration reactions, in the case of the 10 and 20% substituted pastes.     

Principal component and cluster analyses as supporting tools for co-crystals detection

The effects of super absorbent polymer (SAP) on the early hydration evolution of Portland cement within 72 h were investigated by isothermal calorimetry, thermal analysis and X-ray diffraction analysis. The results show that the SAP definitely affects the early hydration process of Portland cement, increases the hydration heat evolution rate during the acceleration period and during the main exothermic peak, promotes the earlier appearance of the main exothermic peak, but does not affect the lengths of the initial reaction period and the induction period and the onset of the acceleration period. The SAP can accelerate cement hydration to increase the hydration degree within 72 h. But the dosage variation of SAP has minor influence on the hydration heat evolution and hydration degree. The SAP enhances the formation of Ca(OH)₂ after 12 h to keep higher content than that in the reference paste. The SAP does not affect the maximum content of ettringite, but delays the conversion of ettringite to monosulphate to remain ettringite content higher at later hydration time. Besides, no new phases are found to have formed in cement paste with SAP.     

Effect of the degree of substitution on the rheology of sodium carboxymethylcellulose solutions in propylene glycol/water mixtures

The linear dynamic viscoelastic properties and non-linear transient rheology of sodium carboxymethylcellulose solutions (Na-CMC) in propylene glycol/water mixtures were investigated. Measurements were carried out for the solutions of Na-CMC with three different degrees of substitution (DS), namely 0.62, 0.79, 1.04, and the similar average molecular weight (M_w ≈ 250,000 g/mol). The strong synergism between the molecules of Na-CMC with DS of 0.62 and 0.79, and propylene glycol has been observed. The occurrence of the overshoot shear stress and the low loss tangent values indicate the physical cross-linking of the polymer chains. The increase of propylene glycol concentration over 80 wt% and sodium carboxymethylcellulose (DS = 0.7) over 1.6 wt% leads to the formation of a physical cross-link network. The absence of overshoot shear stress and terminal behaviour in SAOS flow of the Na-CMC_1.04 solutions in the PG/water mixture shows that no intermolecular cross-linking of polymer chains occurred in them.     

Classification of amino acids and oligopeptides with the use of multi-mode chemical images obtained with ion selective electrode array

The analysis of amino acids and oligopeptides as important bioanalytes is a significant task in medical diagnostics and proteomic research and currently it is based on chromatographic and electrophoretic methods. In this paper, an approach based on sensor array coupled with titration is proposed for effective recognition of 5 amino acids and 4 oligopeptides. It is shown, that the increase of information gained during measurements of sensors’ signals in various pH allows for capturing more data on interaction of amino acids and oligopeptides with various polymeric membranes of potentiometric electrodes used in the array, and that leads to the lowering of classification errors in partial least squares analysis.