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A Burkholderia sacchari cell factory: production of poly-3-hydroxybutyrate, xylitol and xylonic acid from xylose-rich sugar mixtures

Publication . Raposo, Rodrigo S.; Almeida, M. Catarina M. D. de; Fonseca, M. Manuela da; Cesário, M. Teresa

"Efficient production of poly-3-hydroxybutyrate (P(3HB)) based on glucose-xylose mixtures simulating different types of lignocellulosic hydrolysate (LCH) was addressed using Burkholderia sacchari, a wild strain capable of metabolizing both sugars and producing P(3HB). Carbon catabolite repression was avoided by maintaining glucose concentration below 10g/L. Xylose concentrations above 30g/L were inhibitory for growth and production. In fed-batch cultivations, pulse size and feed addition rate were controlled in order to reach high productivities and efficient sugar consumptions. High xylose uptake and P(3HB) productivity were attained with glucose-rich mixtures (glucose/xylose ratio in the feed=1.5w/w) using high feeding rates, while with xylose-richer feeds (glucose/xylose=0.8w/w), a lower feeding rate is a robust strategy to avoid xylose build-up in the medium. Xylitol production was observed with xylose concentrations in the medium above 30-40g/L. With sugar mixtures featuring even lower glucose/xylose ratios, i.e. xylose-richer feeds (glucose/xylose=0.5), xylonic acid (a second byproduct) was produced. This is the first report of the ability of Burkholderia sacchari to produce both xylitol and xylonic acid."

2017-01Journal article

Restricted access

Ocular drug delivery from contact lenses: mimetizing the hydrodynamic conditions of the eye

Publication . Pimenta, Andreia; Valente, Ana; Pereira, José M. C.; Pereira, José C. F.; Filipe, Helena; Mata, José L. G.; Colaço, Rogério; Saramago, Benilde; Serro, Ana Paula

2016-09-25Conference object

Open access

Effect of sterilization on drugs and lenses for ophthalmic applications

Publication . Topete, Ana; Oliveira, Andreia; Galante, Raquel; Bozukova, Dimitriya; Saramago, Benilde; Serro, A. P.

2016-05-17Conference object

Open access

Interaction of the Alzheimer Aβ(25–35) peptide segment with model membranes

Publication . Cuco, Andreia; Serro, Ana Paula; Farinha, José Paulo; Saramago, Benilde; Silva, Amélia Gonçalves da

Alzheimer’s disease is characterized by the presence of amyloid plaques in the brain. The main components of these plaques are the Aβ(1–40) and Aβ(1–42) peptides but the Aβ(25–35) sequence is the most frequently studied fragment because it represents a biologically active region of the longer Aβ peptides. In the present work, the interactions of Aβ(25–35) peptide with model membranes were investigated, taking into consideration the aggregation state of the peptide. Monolayers and liposomes were taken as model membranes with two lipid compositions: the equimolar ternary mixture of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), sphingomyelin (SM), and cholesterol (Chol) and the equimolar POPC/SM binary mixture. The interaction of Aβ(25–35) with the monolayers, investigated at low concentrations (0.25–4 μM), suggested a three step mechanism: adsorption—monomers or dimers adsorb at the polar region of the lipid monolayer; nucleation—adsorbed peptides act as nucleation sites for higher aggregates; and penetration—these aggregates insert in the hydrophobic region of the monolayer. Chol slightly enhances the peptide–lipid monolayer interaction. The large aggregates nucleated in the bulk solution evidenced a weak interaction with monolayers. The interaction of Aβ(25–35) with liposomes, followed by a Quartz Crystal Microbalance with Dissipation (QCM-D) in a large range of peptide concentrations (10–80 μM), was very small, independently of the peptide concentration.

2016-05Journal article

Restricted access

Chitosan/alginate based multilayers to control drug release fromophthalmic lens

Publication . Silva, Diana; Pinto, Luís F. V.; Bozukova, Dimitriya; Santos, Luís F.; Serro, Ana Paula; Saramago, Benilde

In this study we investigated the possibility of using layer-by-layer deposition, based in natural polymers (chitosan and alginate), to control the release of different ophthalmic drugs from three types of lens materials: a silicone-based hydrogel recently proposed by our group as drug releasing soft contact lens (SCL) material and two commercially available materials: CI26Y for intraocular lens (IOLs) and Definitive 50 for SCLs. The optimised coating, consisting in one double layer of (alginate – CaCl2)/(chitosan + glyoxal) topped with a final alginate-CaCl2 layer to avoid chitosan degradation by tear fluid proteins, proved to have excellent features to control the release of the anti-inflammatory, diclofenac, while keeping or improving the physical properties of the lenses. The coating leads to a controlled release of diclofenac from SCL and IOL materials for, at least, one week. Due to its high hydrophilicity (water contact angle ≈ 0) and biocompatibility, it should avoid the use of further surface treatments to enhance the useŕs comfort. However, the barrier effect of this coating is specific for diclofenac, giving evidence to the need of optimizing the chemical composition of the layers in view of the desired drug.

2016-11Journal article

Open access