Carla Joana Silva - Academia.edu (original) (raw)

Papers by Carla Joana Silva

Polymer Degradation and Stability, 2021

In a pandemic context, personal protective equipment (PPE) as protective clothing is essential to... more In a pandemic context, personal protective equipment (PPE) as protective clothing is essential to ensure the safety of health professionals, caregivers and patients. Although most of the PPE is disposable, it can be effectively and safely reused once sterilized and washed, as long as they keep an adequate performance. The reuse of PPE also brings unquestionable benefits both in economic and environmental terms. This work aims to evaluate the possibility of using gamma irradiation to sterilize textile materials, with different compositions, intended to be used in the production of PPE. It was determined the number of cycles of sterilization followed by washing + drying that each material was able to withstand, while keeping adequate properties. Changes in morphology, colour, wettability, liquid permeability, and mechanical resistance of the materials were evaluated after different number of cycles and related with modifications in their chemical structure and eventual physical degradation. It was found that two materials, a Jersey knitted fabric 50% cotton/50% polyester and a Twill woven fabric 100% polyester, both coated with a 100% polyurethane membrane (samples A2 and A6, respectively) were able to withstand at least 20 cycles without suffering significant morphological or structural modifications. More, sterilization tests proved that even after that number of cycles, the materials can be efficiently sterilized by gamma irradiation. These results will allow more time to refill supply stocks, in case of an exceptional event such as a pandemic outbreak.

Diagnostics

Infectious diseases are an existential health threat, potentiated by emerging and re-emerging vir... more Infectious diseases are an existential health threat, potentiated by emerging and re-emerging viruses and increasing bacterial antibiotic resistance. Targeted treatment of infectious diseases requires precision diagnostics, especially in cases where broad-range therapeutics such as antibiotics fail. There is thus an increasing need for new approaches to develop sensitive and specific in vitro diagnostic (IVD) tests. Basic science and translational research are needed to identify key microbial molecules as diagnostic targets, to identify relevant host counterparts, and to use this knowledge in developing or improving IVD. In this regard, an overlooked feature is the capacity of pathogens to adhere specifically to host cells and tissues. The molecular entities relevant for pathogen–surface interaction are the so-called adhesins. Adhesins vary from protein compounds to (poly-)saccharides or lipid structures that interact with eukaryotic host cell matrix molecules and receptors. Such in...

U.Porto Journal of Engineering, 2020

In the last years, sustainable practices have been developed to minimize the negative effects of ... more In the last years, sustainable practices have been developed to minimize the negative effects of production and excessive consumption on the environment. The textile and clothing industry is one of the most polluting industries globally and needs to rethink its strategies. The fast-fashion caused an increase in production, and the environmental weight associated with the textile industry also increased. The problems range from the enormous expenditure of water resources to the carbon and greenhouse gas emissions to reaching the consumer. This review focuses on the eco-friendly approaches taken by the industry towards supportable apparel manufacturing, from the choice of raw materials to the last step in the textile industry.

Biosensors, 2021

Infectious agents, especially bacteria and viruses, account for a vast number of hospitalisations... more Infectious agents, especially bacteria and viruses, account for a vast number of hospitalisations and mortality worldwide. Providing effective and timely diagnostics for the multiplicity of infectious diseases is challenging. Conventional diagnostic solutions, although technologically advanced, are highly complex and often inaccessible in resource-limited settings. An alternative strategy involves convenient rapid diagnostics which can be easily administered at the point-of-care (POC) and at low cost without sacrificing reliability. Biosensors and other rapid POC diagnostic tools which require biorecognition elements to precisely identify the causative pathogen are being developed. The effectiveness of these devices is highly dependent on their biorecognition capabilities. Naturally occurring biorecognition elements include antibodies, bacteriophages and enzymes. Recently, modified molecules such as DNAzymes, peptide nucleic acids and molecules which suffer a selective screening lik...

Materials Today Communications, 2021

Modification of PET surfaces with Gum Arabic towards its bacterial anti-adhesiveness using an exp... more Modification of PET surfaces with Gum Arabic towards its bacterial anti-adhesiveness using an experimental factorial design approach, Materials Today Communications,

Carbohydrate Polymers, 2016

This work studied the physical immobilization of a commercial laccase on bacterial nanocellulose ... more This work studied the physical immobilization of a commercial laccase on bacterial nanocellulose (BNC) aiming to identify the laccase antibacterial properties suitable for wound dressings. Physico-chemical analysis demonstrates that the BNC structure is manly formed by pure crystalline I␣ cellulose. The pH optimum and activation energy of free laccase depends on the substrate employed corresponding to pH 6, 7, 3 and 57, 22, 48 kJ mol −1 for 2,6-dimethylphenol (DMP), catechol and 2,2-azino-bis-(3ethylbenzothiazoline-6-sulfonic acid) (ABTS), respectively. The Michaelis-Menten constant (Km) value for the immobilized laccase (0.77 mM) was found to be almost double of that of the free enzyme (0.42 mM). However, the specific activities of immobilized and free laccase are similar suggesting that the cage-like structure of BNC allows entrapped laccase to maintain some flexibility and favour substrate accessibility. The results clearly show the antimicrobial effect of laccase in Gram-positive (92%) and Gram-negative (26%) bacteria and cytotoxicity acceptable for wound dressing applications.

Tables 3 Statistical analysis for each of the response variables is summarized in. According to t... more Tables 3 Statistical analysis for each of the response variables is summarized in. According to the Student's test. The statistical analysis for each of the response variables is summarized in Tables 3. According to the Student's test, the factor with most significant effect (99 % confidence level in most cases) on all responses was the time of dyeing. Table 4 Attained models for the responses studied Conclusions This study was an attempt to optimize the process variables of a novel laccase assisted dyeing process of wool. The adopted statistical techniques demonstrated their usefulness in finding the optimal modifier and enzyme concentration, and duration of the process to achieve different depth of colour and hue on the fabrics. Increasing the reaction time, and minimizing the enzyme and modifiers loading could obtain darker colouration of the samples. This renders the laccase dyeing an economically attractive alternative to the conventional high water, dyes, auxiliaries and energy consuming acid dyeing of wool. Additionally the enzymatic reaction was carried out at safe to the textile material pH and temperature. The dyeing experiments with two modifiers having the same molecular weight, but with different position of the substitutes revealed the potential of the enzymatic approach for achieving large diversity of colours and hues on the fabrics, varying the starting compounds.The statistical analysis showed that resorcinol should be used in low concentration to attain deep shade dyeing. Microscopic observation of the cross-section of the enzymatically dyed wool demonstrated penetration of the colorant into the mass of the fibres.

amide and ester groups, respectively, into carboxylic acids. These reactions can be very useful f... more amide and ester groups, respectively, into carboxylic acids. These reactions can be very useful for the treatment of synthetic fibres containing these groups. The enzymatic action causes an increase of charged groups at the surface, improving water absorption (increase hydrofility) and dyeability. Due to enzymatic modification, the acrylic fibers became more hydrophilic and dye uptake was enhanced at temperatures below glass transition. Nitrilase action on PAN fibres was monitored by measuring the release of ammonia and by FTIR detection of the formed of carboxylic groups by diffuse reflectance. Cutinase were used on polyester fibres. The esterase action on polyester fibres promotes an increase of OH and COOH end groups. The OH end groups can be detected by a titration method and measuring the K/S spectrophotometrically after dyeing with a cotton reactive dye. Similarly enzyme preparations showing amidase activity towards polyamide fibres, promote an increase of NH 2 and COOH end groups. The amine groups were detected by a titration method with an increase of the molecular mass on treated samples. When samples were dyed with a wool reactive dye uptake was enhanced at temperatures below glass transition of polyamide.

Electrospinning allows the production of polymer fibres with diameters in the sub-micron size ran... more Electrospinning allows the production of polymer fibres with diameters in the sub-micron size range, through the application of an external electric field, keeping intact the bulk properties of the polymers. Electrospun membranes possess some unique structural features, such as a high surface to volume ratio and very good mechanical performance, properties that are determinant to their use in several applications such as air and liquid filtration, tissue engineering, optical and chemical sensors [1]. In this work, alkali and acid biopolysaccharides blended with polyvinyl alcohol (PVA) were electrospinned into a polyvinylidene difluoride (PVDF) basal microfiltration membrane, with the goal of developing a mid-layer nanofibrous porous support for exploitable thin-film composite (TFC) membranes for water filtration. The alkali and acid biopolysaccharides chosen were, respectively, chitosan (CS), a cationic polyelectrolyte (in this case with deacetylation degree around 85), and cyanobac...

Biotechnology Techniques - BIOTECHNOL TECHNIQUE, 1999

Fourteen assays were conducted to study the influence of different variables, namely xylose conce... more Fourteen assays were conducted to study the influence of different variables, namely xylose concentration, inoculum level, agitation speed and nutrient supplementation, on xylitol biosynthesis by Candida guilliermondii FTI 20037. The maximum predicted values for xylitol yield (0.65 g g-1) and xylitol productivity (0.66 g l-1 h-1) can be attained with rice straw hydrolysate containing 60 g xylose l-1 without supplementation of ammonium sulfate, calcium chloride and rice bran extract, using 5 g inoculum l-1, at 250 rpm. Xylose concentration and inoculum level were selected for further optimization studies.

Process Biochemistry, 2001

ABSTRACT The combined effects of initial xylose concentration and inoculum level on xylitol produ... more ABSTRACT The combined effects of initial xylose concentration and inoculum level on xylitol production by Candida guilliermondii from rice straw hydrolysate were studied using response surface methodology. A 22 full-factorial central composite design was employed for experimental design and analysis of the results. The optimum xylose concentration and inoculum level were found to be 82 and 3 g/l, respectively. In these conditions, xylitol concentration of 52 g/l with a production rate of 0.54 g/l and a yield factor of 0.65 g/g was attained. These results are in close agreement with the model predictions.

Letters in Applied Microbiology, 2001

To evaluate a simple and economical technique to improve xylitol production using concentrated xy... more To evaluate a simple and economical technique to improve xylitol production using concentrated xylose solutions prepared from rice straw hemicellulosic hydrolysate. Experiments were carried out with rice straw hemicellulosic hydrolysate containing 90 g l-1 xylose, with and without the addition of nutrients, using the yeast Candida guilliermondii previously grown on the hydrolysate (adapted cells) or on semi-defined medium (unadapted cells). By this method, the yield of xylitol increased from 17 g l-1 to 50 g l-1, and xylose consumption increased from 52% to 83%, after 120 h of fermentation. The xylitol production rates were very close to that (0.42 g l-1 h-1) attained in a medium simulating hydrolysate sugars. Yeast strain adaptation to the hydrolysate showed to be a suitable method to alleviate the inhibitory effects of the toxic compounds. Adapted cells of Candida guilliermondii can efficiently produce xylitol from hydrolysate with high xylose concentrations. Yeast adaptation helps the bioconversion process in hydrolysate made from lignocellulosic materials. This low-cost technique provides an alternative to the detoxification methods used for removal of inhibitory compounds. In addition, the use of adapted inocula makes it possible to schedule a series of batch cultures so that the whole plant can be operated almost continuously with a concomitant reduction in the overall operation time.

Journal of Food Engineering, 2006

The kinetic behaviour of the yeast Candida guilliermondii FTI 20037 was evaluated on a bench bior... more The kinetic behaviour of the yeast Candida guilliermondii FTI 20037 was evaluated on a bench bioreactor using rice straw hydrolysate as a substrate. The maximum xylitol concentration (45.4 g l À1) was attained after 45 h of fermentation, which corresponded to a xylitol volumetric productivity of 1.01 g l À1 h À1. This value was improved in about 90% when compared to the results attained with aerated flasks (0.54 g l À1 h À1). The kinetic results obtained in the present work reinforce the idea that rice straw hydrolysate constitutes an effective xylose source for xylitol production.

Journal of Chemical Technology & Biotechnology, 2005

A full factorial design was used to study the influence of four different variables, namely polym... more A full factorial design was used to study the influence of four different variables, namely polymer concentration, carbodiimide concentration, time of reaction and blocking agent concentration, on the coupling of a serine protease into a soluble-insoluble polymer (Eudragit S-100). All of the four factors studied have played a critical role in the protease coupling. Response surface methodology was used as an optimisation strategy to attain a conjugate with high activity yield and operational stability at 60 • C. Under optimised conditions (Eudragit, 2.5% w/v, carbodiimide, 0.2% w/v, coupling time, 1 h and blocking agent concentration, 0.05%), the conjugate activity yield was about 45% and its operational stability at 60 • C was increased by 1.7 times. After reusing the conjugate for five cycles, the remaining activity was still 72% of the initial value when compared with the native enzyme. Several tests confirmed that the enzyme was covalently crosslinked to Eudragit, which represents an improvement in the carbodiimide coupling of proteases into soluble-insoluble polymers.

Biocatalysis and Biotransformation, 2008

ABSTRACT The protease Esperase® was modified by covalent bonding with two grades of a reversible ... more ABSTRACT The protease Esperase® was modified by covalent bonding with two grades of a reversible soluble-insoluble co-polymer of methacrylic acid and methyl-methacrylate, namely Eudragit® L 100 and Eudragit® S 100. The optimum reaction conditions and washing protocol were investigated and it was found that Esperase® modified with Eudragit® L 100 showed greater activity than if modified with Eudragit® S 100. This should be expected as there is a greater quantity of active sites, namely carboxyl groups, per mass of Eudragit® L 100 in comparison with Eudragit® S 100 to interact with the enzyme. Gel filtration confirmed that Eudragit® L 100 covalently bonded to Esperase®. Treatment of the modified Esperase® on wool showed that the enzyme modified with Eudragit® L 100 had greater activity towards the wool and appeared more effective in shrink resistant finishing.

Applied Microbiology and Biotechnology, 2006

Semidefined media fermentation simulating the sugar composition of hemicellulosic hydrolysates (a... more Semidefined media fermentation simulating the sugar composition of hemicellulosic hydrolysates (around 85 g l-1 xylose, 17 g l-1 glucose, and 9 g l-1 arabinose) was investigated to evaluate the glucose and arabinose influence on xylose-to-xylitol bioconversion by Candida guilliermondii. The results revealed that glucose reduced the xylose consumption rate by 30%. Arabinose did not affect the xylose consumption but its utilization by the yeast was fully repressed by both glucose and xylose sugars. Arabinose was only consumed when it was used as a single carbon source. Xylitol production was best when glucose was not present in the fermentation medium. On the other hand, the arabinose favored the xylitol yield (which attained 0.74 g g-1 xylose consumed) and it did not interfere with xylitol volumetric productivity (Q P = 0.85 g g-1), the value of which was similar to that obtained with xylose alone.

Food Technology and …, 2004

Summary In this work the effect of crosslinking the enzyme esperase (EC 3.4.21.62) and the protei... more Summary In this work the effect of crosslinking the enzyme esperase (EC 3.4.21.62) and the proteins bovine serum albumin and casein with the bifunctional compound glutaraldehyde on molecular mass increase was studied. Two common techniques for measuring molecular ...

Enzyme and Microbial Technology, 2007

The possibility to use cotton as a matrix for controlled release systems was studied by covalentl... more The possibility to use cotton as a matrix for controlled release systems was studied by covalently attaching a model compound, specifically the reactive dye Remazol Brilliant Blue R to its surface. Afterwards the fabric was coated with a commercial cellulase. The release of the dye, obtained by the hydrolysis of cotton fibres in sweat buffer, was monitored. The reducing sugars concentration increased for both fabrics (with and without the dye covalently fixed) while the increase in the absorbance was only attained for the dyed cotton, as expected. These results confirm the viability of using cotton as a natural matrix for controlled released systems while presenting a promising approach to immobilize covalently other substances in cotton garments, like fragrances, which could be released by the action of human sweat.

Enzyme and Microbial Technology, 2006

A commercial protease, Esperase, was covalently linked to Eudragit S-100, a reversible soluble-in... more A commercial protease, Esperase, was covalently linked to Eudragit S-100, a reversible soluble-insoluble polymer by carbodiimide coupling. When compared to the native enzyme, the immobilized form presented a lower specific activity towards high molecular weight substrates but a higher thermal stability at all temperatures tested. The optimum pH of the immobilized protease was shifted towards the alkaline side by about one pH unit while there was no change in optimum temperature between the free and immobilized protease. The immobilized protease exhibited a good storage stability and re-usability. Enzymatic treatment of wool using proteases has been investigated for wool shrink-resist finishing. It was found that using the immobilized protease in the enzymatic treatment of wool there was a reduction of weight and fibre tensile strength loss because the proteolytic attack is only limited to the cuticle surfaces of wool fibres. This novel approach is a promising alternative for wool shrink-resist finishing to replace the conventional chlorine treatments. This environmentally friendly bioprocess needs to be further characterized to a complete understanding and optimization.