Production of fatty acid methyl esters and bioactive compounds from citrus wax.

Citrus wax is a waste generated during the purification process of the citrus essential oil. A lot of citrus wax wastes are globally produced, despite this, its composition and properties are not well known. Here we present comprehensive results proving the chemical composition and the physical properties of citrus wax. Additionally, our study provides the basis for obtaining value-added products from citrus wax wastes. The qualitative/quantitative analysis revealed the presence of different compounds, which range from flavonoids, saponins, carbohydrates, unsaturated compounds, phenolic hydroxyls, and long-chain fatty acid esters. Given that citrus wax is a source of many bioactive compounds, they were preferably extracted with ethanol. The ethanolic extracts demonstrated the presence in citrus wax of different bioactives, such as 5-5'-dehydrodiferulic acid, 3,7-dimethylquercetin, 5,6-dihydroxy-7,8,3',4'-tetramethoxyflavone, tangeretin, and limonene. After the extraction of bioactives from citrus wax, a washed waxy material with high content of long-chain fatty acid esters was obtained. It was shown that this washed wax can be used for the production of biodiesel. The transesterification reactions in acid media was the preferred process because higher content of fatty acid methyl esters (such as hexadecanoic acid methyl ester and 9,12-octadecadienoic acid (Z,Z)-, methyl ester) were obtained. Currently, citrus wax does not have any industrial application, here we shown that under the concept of waste biorefinery, the citrus wax wastes are useful sources for producing value-added products such as bioactive compounds and biodiesel.

Polyethylene glycol-based low generation dendrimers functionalized with ß-cyclodextrin as cryo- and dehydro-protectant of catalase formulations.

Polyethylene glycol (PEG)-based low generation dendrimers are analyzed as single excipient or combined with trehalose in relation to their structure and efficiency as enzyme stabilizers during freeze-thawing, freeze-drying, and thermal treatment. A novel functional dendrimer (DGo -CD) based on the known PEG's ability as cryo-protector and ß-CD as supramolecular stabilizing agent is presented. During freeze-thawing, PEG and ß-CD failed to prevent catalase denaturation, while dendrimers, and especially DGo -CD, offered the better protection to the enzyme. During freeze-drying, trehalose was the best protective additive but DGo -CD provided also an adequate catalase stability showing a synergistic behavior in comparison to the activities recovered employing PEG or ß-CD as unique additives. Although all the studied dendrimers improved the enzyme remaining activity during thermal treatment of freeze-dried formulations, the presence of amorphous trehalose was critical to enhance enzyme stability. The crystallinity of the protective matrix, either of PEG derivatives or of trehalose, negatively affected catalase stability in the freeze-dried systems. When humidified at 52% of relative humidity, the dendrimers delayed trehalose crystallization in the combined matrices, allowing extending the protection at those conditions in which normally trehalose fails. The results show how a relatively simple covalent combination of a polymer such as PEG with ß-CD could significantly affect the properties of the individual components. Also, the results provide further insights about the role played by polymer-enzyme supramolecular interactions (host-guest crosslink, hydrogen bonding, and hydrophobic interactions) on enzyme stability in dehydrated models, being the effect on the stabilization also influenced by the physical state of the matrix.