Browsing by Author "Bernardo, Marisa"
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- Biodegradation rate constants in different NF/UF fractions of cork processing wastewatersPublication . Bernardo, Marisa; Santos, Ana; Cantinho, Paula; Minhalma, MiguelCork processing wastewater is an aqueous complex mixture of organic compounds that have been extracted from cork planks during the boiling process. These compounds, such as polysaccharides and polyphenols, have different biodegradability rates, which depend not only on the natureof the compound but also on the size of the compound. The aim of this study is to determine the biochemical oxygen demands (BOD) and biodegradationrate constants (k) for different cork wastewater fractions with different organic matter characteristics. These wastewater fractions were obtained using membrane separation processes, namely nanofiltration (NF) and ultrafiltration (UF). The nanofiltration and ultrafiltration membranes molecular weight cut-offs (MWCO) ranged from 0.125 to 91 kDa. The results obtained showed that the biodegradation rate constant for the cork processing wastewater was around 0.3 d(-1) and the k values for the permeates varied between 0.27-0.72 d(-1), being the lower values observed for permeates generated by the membranes with higher MWCO and the higher values observed for the permeates generated by the membranes with lower MWCO. These higher k values indicate that the biodegradable organic matter that is permeated by the membranes with tighter MWCO is more readily biodegradated.
- Cork industry wastewater characterization assessment of the biodegradability, reuse and of the relationship between BOD, COD and tannins with TOCPublication . Santos, Ana; Bernardo, Marisa; Vespeira, Carla; Cantinho, Paula; Minhalma, MiguelCork processing involves a boiling step to make the cork softer, which consumes a high volume of water and generates a wastewater with a high organic content, rich in tannins. An assessment of the final wastewater characteristics and of the boiling water composition along the boiling process was performed. The parameters studied were pH, color, total organic carbon (TOC), chemical and biochemical oxygen demands (COD, BOD5, BOD20), total suspended solids (TSS), total phenols and tannins (TP, TT). It was observed that the water solutes extraction power is significantly reduced for higher quantities of cork processed. Valid relationships between parameters were established not only envisaging wastewater characterization but also to provide an important tool for wastewater monitoring and for process control/optimization. Boiling water biodegradability presented decreasing values with the increase of cork processed and for the final wastewater its value is always lower than 0.5, indicating that these wastewaters are very difficult to treat by biological processes. The biodegradability was associated with the increase of tannin content that can rise up to 0.7 g/L. These compounds can be used by other industries when concentrated and the clarified wastewater can be reused, which is a potential asset in this wastewater treatment.
- Cork industry wastewater partition by ultra/nanofiltration: A biodegradation and valorisation studyPublication . Bernardo, Marisa; Santos, Ana; Cantinho, Paula; Minhalma, MiguelWastewater from cork processing industry present high levels of organic and phenolic compounds, such as tannins, with a low biodegradability and a significant toxicity. These compounds are not readily removed by conventional municipal wastewater treatment, which is largely based on primary sedimentation followed by biological treatment. The purpose of this work is to study the biodegradability of different cork wastewater fractions, obtained through membrane separation, in order to assess its potential for biological treatment and having in view its valorisation through tannins recovery, which could be applied in other industries. Various ultrafiltration and nanofiltration membranes where used, with molecular weight cut-offs (MWCO) ranging from 0.125 to 91 kDa. The wastewater and the different permeated fractions were analyzed in terms of Total Organic Carbon (TOC), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Phenols (TP), Tannins, Color, pH and Conductivity. Results for the wastewater shown that it is characterized by a high organic content (670.5-1056.8 mg TOC/L, 2285-2604 mg COD/L, 1000-1225 mg BOD/L), a relatively low biodegradability (0.35-0.38 for BODs/COD and 0.44-0.47 for BOD20/COD) and a high content of phenols (360-410 mg tannic acid/L) and tannins (250-270 mg tannic acid/L). The results for the wastewater fractions shown a general decrease on the pollutant content of permeates, and an increase of its biodegradability, with the decrease of the membrane MWCO applied. Particularly, the permeated fraction from the membrane MWCO of 3.8 kDa, presented a favourable index of biodegradability (0.8) and a minimized phenols toxicity that enables it to undergo a biological treatment and so, to be treated in a municipal wastewater treatment plant. Also, within the perspective of valorisation, the rejected fraction obtained through this membrane MWCO may have a significant potential for tannins recovery. Permeated fractions from membranes with MWCO lower than 3.8 kDa, presented a particularly significant decline of organic matter and phenols, enabling this permeates to be reused in the cork processing and so, representing an interesting perspective of zero discharge for the cork industry, with evident environmental and economic advantages. (C) 2010 Elsevier Ltd. All rights reserved.
- Ensino e aprendizagem da geometriaPublication . Rodrigues, Margarida; Bernardo, MarisaEste simpósio tem como objectivo apresentar e discutir estudos incidentes no ensino e na aprendizagem da Geometria Começamos por clarificar alguns dos conceitos essenciais a propósito das orientações curriculares actuais e, em seguida, enquadramos as comunicações deste simpósio nas questões de investigação que presentemente se colocam neste domínio
- Optimized Production of Hydroxamic Acid Derivatives with Antioxidant and Anticholinergic Potential by Immobilized Pseudomonas aeruginosa CellsPublication . Bernardo, Marisa; Reis, Telma; Minhalma, Miguel; Karmali, Amin; Serralheiro, Maria Luísa; Pacheco, RitaIn this study were investigated, the synthesis, acetylcholinesterase inhibition and antioxidant activity of a series of hydroxamic acid derivatives (HAD), with different chemical group characteristics, such as aliphatic (acetohydroxamic acid and butyryl hydroxamic acid), aromatic (benzohydroxamic acid and phenylalanine hydroxamic acid) and amino acid (glycine hydroxamic acid and alanine hydroxamic acid). It was observed that these HAD compounds present very promising activity as acetylcholinesterase (AChE) inhibitors and as antioxidants. The aliphatic HAD demonstrated to have a higher inhibitory activity of AChE than amino acid or aromatic HAD. As for the antioxidant activity, a high antioxidant potential was found for all the compounds with EC50 values ranging from 0.19 µM to 1.65 µM. Aiming these applications, a biocatalysis approach was used to obtain these HADs with optimal reactional conditions. In this study, reverse micelles with immobilized Pseudomonas aeruginosa intact cells containing amidase were used as a biocatalyst to catalyze the acyltransferase reaction of the corresponding substrate amide and hydroxylamine to obtain various HAD and this was achieved for the first time with yields of approximately 100 %.
- Production of hydroxamic acids by immobilized Pseudomonas aeruginosa cells Kinetic analysis in reverse micellesPublication . Bernardo, Marisa; Pacheco, Rita; Serralheiro, Maria Luísa M.; Karmali, AminIntact cells from Pseudomonas aeruginosa strain L10 containing amidase were used as biocatalysts both free and immobilized in a reverse micellar system. The apparent kinetic constants for the transamidation reaction in hydroxamic acids synthesis, were determined using substrates such as aliphatic, amino acid and aromatic amides and esters, in both media. In reverse micelles, K-m values decreased 2-7 fold relatively to the free biocatalyst using as substrates acetamide, acrylamide, propionamide and glycinamide ethyl ester. We have concluded that overall the affinity of the biocatalyst to each substrate increases when reactions are performed in the reversed micellar system as opposed to the buffer system. The immobilized biocatalyst in general, exhibits higher stability and faster rates of reactions at lower substrates concentration relatively to the free form, which is advantageous. Additionally, the immobilization revealed to be suitable for obtaining the highest yields of hydroxamic acids derivatives, in some cases higher than 80%. (C) 2013 Elsevier B.V. All rights reserved.