Enzymatic production, physicochemical characterization, and prebiotic potential of pectin oligosaccharides from pisco grape pomace.

The prebiotic capacity of Pectin Oligosaccharides (POS) is influenced by structural factors such as molecular size, composition, and degree of esterification, which affect their interaction with the gut microbiota. While existing literature has predominantly examined POS derived from apple and citrus pectins, the extrapolation of these findings to other pectin sources remains complex due to variations in their composition. This study focused on obtaining POS with prebiotic potential from pisco grape pomace through controlled enzymatic hydrolysis, resulting in three molecular size fractions: <3 kDa, 3-10 kDa, and > 10 kDa. The POS fractions were analyzed using FTIR, HPSEC, HPLC, and MALDI-TOF-MS techniques to characterize their physical-chemical properties. Each fraction presented distinct compositions, with the <3 kDa fraction showing a higher concentration of galacturonic acid and glucose, while the >10 kDa fraction was also composed of rhamnose and arabinose. Notably, the <3 kDa fraction supported greater biomass growth of the probiotic strain Lactobacillus casei ATCC 393 compared to the other fractions. In contrast, the non-probiotic strain Escherichia coli ATCC 25922 achieved the lowest biomass with this fraction. Consequently, the <3 kDa POS fraction exhibited the highest prebiotic index. This fraction, composed of oligomers from the rhamnogalacturonan region and arabino-oligosaccharides with a degree of polymerization between two and five, highlights its potential for further research and applications. Therefore, investigating other sources and optimizing extraction conditions could lead to developing novel prebiotic formulations that supply specific probiotic strains for a symbiotic product.

Synthesis of Glycerol Carbonate from Ethylene Carbonate Using Zinc Stearate as a Catalyst: Operating Conditions and Kinetic Modeling.

With the advent of biodiesel as a substitute/additive for diesel, the production of glycerol has experienced an increase, as it is an unavoidable byproduct of the biodiesel process; therefore, novel products and processes based on this triol are being very actively researched. Glycerol carbonate emerges as an advanced humectant from glycerol and a monomer for diverse polycarbonates. Its production in high yields and amounts can be achieved through the solventless transcarbonation of glycerol with other organic carbonates driven by alkaline catalysts, standing out amongst the cyclic carbonates due to its reactivity. Here, we have studied the main operational variables that affect the transcarbonation reaction of glycerol and ethylene carbonate catalyzed by zinc stearate: catalyst concentration, reagent molar ratio, and temperature. Subsequently, an appropriate kinetic model was fitted to all data obtained at 80 °C and several catalyst concentrations as well as reagent molar ratios. Finally, the selected kinetic model was extended and validated by fitting it to data obtained at several temperatures, finding that the activation energy of this reaction with this catalyst is around 69.2 kJ·mol-1. The kinetic model suggests that the reaction is bimolecular and elemental and that the process is interfacial in essence, with the catalyst dispersed in a narrow space between polar (glycerol) and nonpolar (ethylene carbonate) phases.