Effect of liquid-phase surface tension on hydrodynamics of a three-phase airlift reactor with an enlarged degassing zone

The effect of the addition of ethanol (10 g/l) to the liquid-phase on gas and solids holdup, circulation and mixing times and interstitial liquid velocity in a threephase airlift reactor was investigated. The airlift reactor (60 l) is of the concentric draught-tube type with an enlarged degassing zone. Ca-alginate beads were used as solid-phase and airflow rate (from 1.9 to 90.2 l/min) and solids loading (0-30% (v/v)) were manipulated. Riser and downcomer gas holdup were found to increase with the addition of ethanol, leading to a decrease on the relative solids holdup. The presence of ethanol seems to have no influence on the circulation time. On the other hand, mixing time variation depends on the solids loading and airflow rate. Riser and downcomer interstitial liquid velocity are lower for ethanol solution than for water.Junta Nacional de Investigação Científica e Tecnológica (JNICT) - PRAXIS/2/2.1/ BIO/1061/95 , grant GGP XXI/BD/2937/96

Hydrodynamic studies in an airlift reactor with an enlarged degassing zone

The hydrodynamic behaviour of a 60 l threephase airlift bioreactor, of the concentric draught tube type, with an enlarged degassing zone has been studied. Ca-alginate beads were used as the solid phase. Airflow rate (from 1.9 to 90.2 l/min), solids loading (0% to 40% (v/v)) and solids density (1016 and 1038 kg/m³) were manipulated and their influence on solids and gas holdup, circulation and mixing times and in the interstitial liquid velocity was determined. Riser and downcomer solids holdup was found to decrease with the increase of airflow rate and to increase with solids loading and density. On the contrary, gas holdup in the riser and in the downcomer increased with airflow rate and decreased with solids loading and density. By increasing airflow rate, a decrease in circulation time was observed while the effects of solids loading and density were negligible. Mixing time decreased with airflow rate, increased with solids density, in the studied range, and presented a maximum for solids loading of approximately 20% (v/v).Junta Nacional de Investigação Científica e Tecnológica (JNICT) Instituto de Biotecnologia e Química Fina (IBQF) - GGP XXI/BD/2937/9

Oxygen mass transfer in a high solids loading three-phase internal-loop airlift reactor

Determinations of volumetric mass transfer coefficient were conducted in a three-phase internal-loop airlift reactor with an enlarged degassing zone. The effect of parameters such as the airflow rate (riser superficial gas velocities between 0.01 and 0.5 m/s), solids loading (up to 30%, v/v), solids density (1023 and 1048 kg/m3) and the liquid-phase properties on kLa was studied. It was observed that the increase of the airflow rate and the introduction of ethanol enhanced the volumetric mass transfer coefficient in the system. On the contrary, the progressive introduction of solids and a small increase on solids density were responsible for the diminishing of the mass transfer rate. Correlations for the volumetric mass transfer coefficient with the riser superficial gas velocity and solids loading were determined for the two solids density and the two liquid-phases. A good agreement between experimental data and the calculated values was obtained.Instituto de Biotecnologia e Química Fina. Fundação para a Ciência e a Tecnologia -PRAXIS/2/2.1/BIO/1061/95, GGPXXI/BD/2937/96. EC - INCO-COPERNICUS - no. ERB IC15-CT98-0904

Hydrodynamic model for three-phase internal- and external-loop airlift reactors

A mathematical model predicting the hydrodynamic behaviour of three-phase airlift reactors, working with low-density solids and with high solids loading, was developed. The model allows for the prediction of local gas holdup and liquid velocity in airlift bioreactors. Model was validated for an external-loop airlift reactor and an internal-loop airlift reactor with an enlarged degassing zone, being a good agreement obtained between calculated and experimental data.Fundação para a Ciência e a Tecnologia (FCT) Junta Nacional de Investigação Científica e Tecnológica (JNICT) - PRAXIS 2/2.1/BIO/1061/95 Instituto de Biotecnologia e Química Fina (IBQF) - GGP XXI/BD/2937/9

Valorization of agro-industrial wastes towards the production of rhamnolipids

In this work, oil mill wastewater (OMW), a residue generated during olive oil extraction, was evaluated as an inducer of rhamnolipid production. Using a medium containing as sole ingredients corn steep liquor (10%, v/v), sugarcane molasses (10%, w/v) and OMW (25%, v/v), Pseudomonas aeruginosa #112 produced 4.5 and 5.1 g of rhamnolipid per liter in flasks and reactor, respectively, with critical micelle concentrations as low as 13 mg/l. Furthermore, in the medium supplemented with OMW, a higher proportion of more hydrophobic rhamnolipid congeners was observed comparing with the same medium without OMW. OMW is a hazardous waste which disposal represents a serious environmental problem; therefore, its valorization as a substrate for the production of added-value compounds such as rhamnolipids is of great interest. This is the first report of rhamnolipid production using a mixture of these three agro-industrial by-products, which can be useful for the sustainable production of rhamnolipids.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI- 01-0145-FEDER-006684). The authors also thank the FCT for the financial support under the scope of the Project RECI/BBBEBI/ 0179/2012 (FCOMP-01-0124-FEDER-027462). E.J. Gudiña was supported by the Post-Doctoral fellowship CEB-BPD/01/2015/07 from the project UID/BIO/04469/2013, financed by FCT. A.I. Rodrigues was supported by the doctoral Grant SFRH/BD/111600/2015 provided by FCT

In-depth phenolic characterization of iron gall inks by deconstructing representative Iberian recipes

UIDB/50006/2020 PTDC / QUI-OUT / 29925/2017Iron-gall ink is one of the most important inks in the history of western civilization. The deep black colour results from Fe3+ complexes with phenolic compounds available in gall extracts. Unfortunately, it induces the degradation of both ink and support over time. Furthermore, our knowledge of these complex molecular structures is limited. This work aims to overcome this gap, revealing essential information about the complex structures of these pigments and dyes that will create a breakthrough in the next generation of conservation treatments. It presents the first in-depth phenolic identification and quantification of extracts and inks, prepared with and without gum arabic (an essential additive in medieval recipes). Five representative Iberian recipes were selected and prepared. Their phenolic profile was analysed by HPLC–DAD and HPLC–ESI–MS, which revealed that the phenolic compounds present in higher concentration, in the gall extracts, are pentagalloylglucose and hexagalloylglucose (0.15 ± 0.01–32 ± 3 mg/mL), except for one recipe, in which gallic acid is the main phenolic. The influence of the ingredients is also discussed by deconstructing the recipes: extracts of additives as pomegranate peel and solvents used in the extraction of the galls (vinegar and white wine) were characterized.publishersversionpublishe

Hybrid-Trefftz stress element for bounded and unbounded poroelastic media

SUMMARY The equations that govern the dynamic response of saturated porous media are first discretized in time to define the boundary value problem that supports the formulation of the hybrid-Trefftz stress element. The (total) stress and pore pressure fields are directly approximated under the condition of locally satisfying the domain conditions of the problem. The solid displacement and the outward normal component of the seepage displacement are approximated independently on the boundary of the element. Unbounded domains are modelled using either unbounded elements that locally satisfy the Sommerfeld condition or absorbing boundary elements that enforce that condition in weak form. As the finite element equations are derived from first-principles, the associated energy statements are recovered and the sufficient conditions for the existence and uniqueness of the solutions are stated. The performance of the element is illustrated with the time domain response of a biphasic unbounded domain to show the quality of the modelling that can be attained for the stress, pressure, displacement and seepage fields using a high-order, wavelet-based time integration procedure

Effects of ohmic heating on extraction of food-grade phytochemicals from of colored potato

The influence of ohmic heating (OH) through the application of moderate electric fields on phytochemical compounds recovery from colored potato (Solanum tuberosum L. var. Vitelotte) was studied. A BoxBehnken design was used to simultaneously assess the effects of operational parameters such as electric field strength, temperature and process time on the yields of anthocyanins and total phenolic recovery on pretreatment of potato samples. From the analysis of the model, electric field, temperature and time were shown to have independent and interactive effects on the values of extraction yields. Aqueous extraction of phytochemical compounds after pretreatments can be described by using a two-step model involving simultaneous washing and diffusion of the solutes from the samples. Results shows that electrical fields of low energy levels and thermal effects can be combined and optimized into a single step treatment on extraction of anthocyanins and phenolic compounds from vegetable tissues providing high recovery yields with a reduced treatment time, less energy consumption and with no utilization of organic solvents (green extraction).This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01- 0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145- FEDER-000004) funded by European Regional Development Fund under the scope of Norte2020 e Programa Operacional Regional do Norte. The authors Ricardo N. Pereira, H elder Oliveira and Rui M. Rodrigues also thank to FCT their financial grants with references SFRH/BPD/81887/2011, PD/BD/106062/2015 and SFRH/BD/110723/ 2015, respectively