Concept for the valorization of cereal processing waste: Recovery of phenolic acids by using waste-derived tetrahydrofurfuryl alcohol and biochar.

Valorization of agro-food waste by converting it into a renewable resource plays a crucial role in a bio-based circular economy. Therefore, this study was designed to evaluate the suitability of distillery stillage (DS), which comes from alcohol production from cereals, for producing value-added products that can be used synergistically. The main objective was to investigate the usefulness of two substances for the recovery of phenolic acids, which have antioxidant activity, from the liquid fraction of DS: namely, tetrahydrofurfuryl alcohol (THFA) as a solvent and biochar as an adsorbent, both produced from the solid fraction of cereal processing waste. The effect of THFA concentration (80 and 100%) on phenolic acid yield in ultrasound-assisted extraction was studied. The solubilization predictions of phenolic compounds by the Hansen solubility parameters were in accordance with the experimental results: the yield of phenolic acids in the extracts was highest (3.76 µg g-1 dry mass) with 80% THFA. Among the extracted phenolic acids, hydroxycinnamic acids predominated over hydroxybenzoic acids, which may affect the bioactive properties of the extracts and their future applications for industrial purposes. Phenolic acids from the extracts were adsorbed on 17-170 g biochar L-1 and desorbed into water at 40-60 °C. The phenolic acid recovery was highest (∼92%) when the biochar dose was 85 g L-1 and when desorption was performed at 50 °C. After adsorption/desorption, ∼95% of the antioxidant activity of the phenolic acids in the extracts was maintained. As biochar has a smaller specific surface area than commercial powdered activated carbon (PAC), the biochar dose should be about 5 times higher than an equivalent PAC dose for adsorption efficiency above 90%.

Valorization of distillery stillage by polyphenol recovery using microwave-assisted, ultrasound-assisted and conventional extractions.

An increasing understanding of the negative environmental effects of waste discharges has made valorization of distillery by-products to recover added-value compounds a sound option for distillery stillage management. In this study, the recovery of bioactive compounds, i.e. polyphenols, from distillery stillage was performed by microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and conventional solid-liquid extraction (CSLE) to investigate the effects of extraction time, the concentration of ethyl acetate (EA) in a solvent mixture with ethanol and water, and solid-to-solvent ratio on the recovery yield and antioxidant activity of the extracts. The highest yields of total polyphenol content (TPC) (3.73 mg gallic acid equivalent/g) and phenolic acid content (2.51 µg/g) were obtained with 8-min MAE with 70% EA. MAE provided 1.2- and 1.4-times higher yield of phenolic acids and 1.2- and 1.6-times higher antioxidant activity than UAE and CSLE, respectively. Due to the approximately 3-times higher rate of extraction, the ratio between energy consumption and extraction yield was better in MAE than in UAE. Principal component analysis (PCA) showed that the antioxidant activity of the extracts was positively correlated with TPC and phenolic acid content. Six phenolic acids that were identified were present mainly in their free forms (up to 95% of the total), with a predominance of ferulic (up to 0.80 µg/g) and p-coumaric (up to 0.72 µg/g) acids.

Poly(N-vinylimidazole/ethylene glycol dimethacrylate) for the purification and isolation of phenolic acids.

In this study we report the novel polymeric resin poly(N-vinyl imidazole/ethylene glycol dimethacrylate) for the purification and isolation of phenolic acids. The monomer to crosslinker ratio and the porogen composition were optimized for isolating phenolic acids diluted in acetonitrile at normal phase chromatography conditions, first. Acetonitrile serves as polar, aprotic solvent, dissolving phenolic acids but not interrupting interactions with the stationary phase due to the approved Hansen solubility parameters. The optimized resin demonstrated high loading capacities and adsorption abilities particularly for phenolic acids in both, acetonitrile and aqueous solutions. The adsorption behavior of aqueous standards can be attributed to ion exchange effects due to electrostatic interactions between protonated imidazole residues and deprotonated phenolic acids. Furthermore, adsorption experiments and subsequent curve fittings provide information of maximum loading capacities of single standards according to the Langmuir adsorption model. Recovery studies of the optimized polymer in the normal-phase and ion-exchange mode illustrate the powerful isolation properties for phenolic acids and are comparable or even better than typical, commercially available solid phase extraction materials. In order to prove the applicability, a highly complex extract of rosemary leaves was purified by poly(N-vinyl imidazole/ethylene glycol dimethacrylate) and the isolated compounds were identified using UHPLC-qTOF-MS.

Expanded solubility parameter approach. II: p-Hydroxybenzoic acid and methyl p-hydroxybenzoate in individual solvents.

The recently introduced four-parameter extended Hansen approach was used to study the solubility of p-hydroxybenzoic acid and methyl p-hydroxybenzoate in 32 and 35 individual solvents, respectively. The results are compared with those for benzoic acid in 40 solvents. Seventeen of the thirty-two or 53% of the calculated solubilities of p-hydroxybenzoic acid were within the established solubility criterion (i.e., less than 30% error from the experimental value). Twenty-two of thirty-six or 61% of the calculated solubility values for methyl p-hydroxybenzoate met the solubility criterion. Experimental excess free energies of solution for p-hydroxybenzoic acid and methyl p-hydroxybenzoate were plotted against theoretical values using the expanded four-parameter solubility regression equations. From such results, adjustments may be made in the partial solubility parameters to bring the calculated solubilities in line with experimental results. Multiple regression analyses were used to estimate the total solubility parameter and the four partial solubility parameters of the two benzoic acid derivatives. Satisfactory results were obtained for methyl p-hydroxybenzoate, but poor agreement was found for p-hydroxybenzoic acid for the total parameter when compared with the Fedors group contribution method. Both the multiple regression and group contribution methods may yield inaccurate solubility parameters for relatively polar solid solutes. Factor analysis was used to test the adequacy of three- and four-parameter approaches in the evaluation of drug solubility. A principal factor method without iteration and orthogonal factor rotation were used to compare the two expanded solubility parameter approaches.(ABSTRACT TRUNCATED AT 250 WORDS)

[Adaptation of yeasts of the genus Debaryomyces to protocatechuic acid]. / Adaptatsiia drozhzhei roda Debaryomyces k protokatekhovoi kislote.

Among five yeast strains belonging to the genus Debaryomyces that were unable of utilizing aromatic compounds (phenols and hydroxybenzoic acids), three strains, viz. D. kloeckeri BKM-Y-1044, D. marama BKM-Y-100 and D. marama BKM-Y-2045, were adapted to protocatechuic acid. The adapted yeasts utilized protocatechuic acid if its concentration in the medium was 0.1%, but did not utilize it, or did at a very low rate, if the concentration of protocatechuic acid was decreased to 0.05%. The mechanism of adaptation is rare mutations occurring in succession, and the process takes therefore several months. The adaptation seems to be based on reversion of inactivated genes for enzymes involved in the preparative metabolism of protocatechuic acid. Three typical yeast species of the Debaryomyces genus are proposed (D. hansenii, D. kloeckeri and D. konokotinae) which include all of the Debaryomyces species and strains available at the Institute of Microbiology of the USSR Academy of Sciences.