Analysis of Solid-Liquid Interactions in a Model Bioreactor

The aim of this work is to characterize the two-phase fluid dynamics occurring inside a model stirred bioreactor resembling at lab scale the typical design adopted industrially for the production of biogas by fermentation of agricultural scraps. As for the solid-liquid system, water and PMMA particles of average diameter equal to 180 µm, resembling the unfermented crushed scraps industrially employed are selected. The experiments are carried out by two-phase Particle Image Velocimetry, which allows to simultaneously and separately measure the velocity fields of the continuous and of the dispersed phases. The unconventional geometry of the unbaffled stirred tank makes the measurement of the flow field induced by the impellers and the evaluation of the interactions between the solids and the liquid phase particularly challenging. The single-phase mean velocity field is preliminary investigated under both transient and stationary conditions at various impeller speeds. The two phase flow measurements are carried out at average solid mass concentration of 0.5 % and at impeller speeds lower than that corresponding to the just suspended condition, therefore in all the cases a deposit of particles accumulated at the bottom of the tank, modifying its shape. The comparison of the results collected under single- and two-phase condition highlights that the un-suspended solid layer gives rise to a significant variation of the liquid mean and turbulent velocity fields, confirming the strong dependency of the flow field from the features of the tank bottom. These results are associated to the uneven distribution of particles inside the reactor and to consequent very high concentration of solids in the bottom region. Overall, the analysis of the results allows to gain insight into the fluid dynamic behaviour of the model bioreactor and to suggest possible geometrical modifications aimed at improving the performances of the industrial apparatuses

White grape pomace extracts, obtained by a sequential enzymatic plus ethanol-based extraction, exert antioxidant, anti-tyrosinase and anti-inflammatory activities

open9noThe present work aimed at optimizing a two-step enzymatic plus solvent-based process for the recovery of bioactive compounds from white grape (Vitis vinifera L., mix of Trebbiano and Verdicchio cultivars) pomace, the winemaking primary by-product. Phenolic compounds solubilised by water enzyme-assisted and ethanol-based extractions of wet (WP) and dried (DP) pomace were characterised for composition and tested for antioxidant, anti-tyrosinase and anti-inflammatory bioactivities. Ethanol treatment led to higher phenol yields than water extraction, while DP samples showed the highest capacity of releasing polyphenols, most probably as a positive consequence of the pomace drying process. Different compositions and bioactivities were observed between water and ethanol extracts and among different treatments and for the first time the anti-tyrosinase activity of V. vinifera pomace extracts, was here reported. Enzymatic treatments did not significantly improve the total amount of solubilised compounds; Celluclast in DP led to the recovery of extracts enriched in specific compounds, when compared to control. The best extracts (enzymatic plus ethanol treatment total levels) were obtained from DP showing significantly higher amounts of polyphenols, flavonoids, flavanols and tannins and exerted higher antioxidant and anti-tyrosinase activities than WP total extracts. Conversely, anti-inflammatory capacity was only detected in water (with and without enzyme) extracts, with WP samples showing on average a higher activity than DP. The present findings demonstrate that white grape pomace constitute a sustainable source for the extraction of phytochemicals that might be exploited as functional ingredients in the food, nutraceutical, pharmaceutical or cosmetic industries.embargoed_20180708Ferri, Maura; Rondini, Greta; Calabretta, Maria Maddalena; Michelini, Elisa; Vallini, Veronica; Fava, Fabio; Roda, Aldo; Minnucci, Giordano; Tassoni, AnnalisaFerri, Maura; Rondini, Greta; Calabretta, Maria Maddalena; Michelini, Elisa; Vallini, Veronica; Fava, Fabio; Roda, Aldo; Minnucci, Giordano; Tassoni, Annalis

Recovery of polyphenols from red grape pomace and assessment of their antioxidant and anti-cholesterol activities

The present work aimed at the recovery and characterization of polyphenolic compounds extracted from red grape pomace (Vitis vinifera L.), a winemaking by-product. Polyphenolic compounds of wet (WP) and dried (DP) red pomace were recovered by enzymatic digestions and ethanol-based extractions. Fungamyl and Celluclast enzymes were found to be the most effective in enhancing polyphenol release from WP. WP samples showed the highest capacity of releasing polyphenols with 2. h control 24\ub0C and 2. h 1% Celluclast resulting as the best treatments. A significantly lower amount of polyphenols was recovered from DP most probably as a consequence of the pomace drying. The best extracts contained high amounts of total polyphenols, flavonoids, tannins and anthocyanins and exerted antioxidant and cholesterol-lowering activities. The results support the possibility of exploiting the extracts coming from grape processing by-products as ingredients for functional and innovative products in the nutraceutical, pharmaceutical or cosmetic fields