Browsing by Author "Fonseca, M. Manuela R. da"
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- Biodegradable polyesters from agro&industrial by-productsPublication . Almeida, Catarina Dias de; Cavalheiro, João; Raposo, Rodrigo; Cesário, Teresa; Ferreira, Frederico; Ferreira, Bruno; van Keulen, Frederik; Pollet, Eric; Fonseca, M. Manuela R. da
- Efficient P(3HB) extraction from Burkholderia sacchari cells using non-chlorinated solventsPublication . Rosengart, Alessandro; Cesário, M.Teresa; Almeida, M. Catarina M.D. de; Raposo, Rodrigo S.; Espert, Ana; Díaz de Apodaca, Elena; Fonseca, M. Manuela R. da"A technique using safer, non-chlorinated organic solvents for the extraction of poly-3-hydroxybutyrate (P(3HB)) from bacterial cells was developed, aiming to attain high recovery yields and purities. Some solvents were selected from the GlaxoSmithKline guide as sustainable industrial solvents and the solubility of P(3HB) calculated using predictive equations from literature. Based on the calculated solubility values, anisole, cyclohexanone and phenetole were tested as extraction solvents and the relevant process variables (extraction temperature, extraction time and mass of cells/solvent volume ratio) were addressed. Polymer recovery yields of 97% and 93% were obtained with anisole and cyclohexanone, respectively, at 120–130 °C using a cell/solvent ratio of 1.5% (w/v). Maximum polymer purities using these experimental conditions were 98% for both solvents. The recovery yield and the polymer purity attained with chloroform (reference solvent) were 96 and 98%, respectively. Higher cell/solvent ratios of 6.0% (w/v) showed slightly lower recovery yields and purities. The average molecular weight and the thermal properties of the polymers extracted with the alternative solvents were fully comparable to those of the polymers obtained by chloroform extraction, demonstrating that the applied conditions did not significantly alter the properties of the extracted P(3HB)."
- Enhanced bioproduction of poly-3-hydroxybutyrate from wheat straw lignocellulosic hydrolysatesPublication . Cesário, M. Teresa; Raposo, Rodrigo S.; Almeida, M. Catarina M. D. de; Keulen, Frederik van; Ferreira, Bruno S.; Fonseca, M. Manuela R. da"Polyhydroxyalkanoates (PHAs) are bioplastics that can replace conventional petroleum derived products in various applications. One of the major barriers for their widespread introduction in the market is the higher production costs when compared with their petrochemical counterparts. In this work, a process was successfully implemented with high productivity based on wheat straw, a cheap and readily available agricultural residue, as raw material. The strain Burkholderia sacchari DSM 17165 which is able to metabolize glucose, xylose and arabinose, the main sugars present in wheat straw hydrolysates (WSH), was used. Results in shake flask showed that B. sacchari cells accumulated ca 70 % g P(3HB)/g cell-dry-weight with a yield of polymer on sugars (YP/S) of 0.18 g/g when grown on a mixture of commercial C6 and C5 sugars (control), while these values reached ca 60 % g P(3HB)/g cell-dry-weight and 0.19 g/g, respectively, when WSHs were used as carbon source. In fed-batch cultures carried out in 2L stirred tank reactors on WSH, a maximum polymer concentration of 105 g/L was reached after 61 h of cultivation corresponding to an accumulation of 72% of CDW. Polymer yield and productivity were 0.22 g P(3HB)/g total sugar consumed and 1.6 g/L. h, respectively. The selected feeding strategy successfully overcame the carbon catabolite repression phenomenon observed in sugar mixtures containing hexoses and pentoses. This is the first work describing fed-batch cultivations aiming at PHA production using real lignocellulosic hydrolysates. Additionally, the P(3HB) volumetric productivities attained are, by far, the highest achieved ever on agricultural wastes hydrolysates."
- Marine algal carbohydrates as carbon sources for the production of biochemicals and biomaterialsPublication . Cesário, M. Teresa; Fonseca, M. Manuela R. da; Marques, Mafalda M.; Almeida, M. Catarina. M. D. deThe high content of lipids in microalgae (>60% w/w in some species) and of carbohydrates in seaweed (up to 75%) have promoted intensive research towards valorisation of algal components for the production of biofuels. However, the exploitation of the carbohydrate fraction to produce a range of chemicals and chemical intermediates with established markets is still limited. These include organic acids (e.g. succinic and lactic acid), alcohols other than bioethanol (e.g. butanol), and biomaterials (e.g. polyhydroxyalkanoates). This review highlights current and potential applications of the marine algal carbohydrate fractions as major C-source for microbial production of biomaterials and building blocks.
- Production of poly (3-hydroxybutyrate-co-4-hydroxybutyrate) by Burkholderia sacchari using wheat straw hydrolysates and gamma-butyrolactonePublication . Cesário, M. Teresa; Raposo, Rodrigo S.; Almeida, M. Catarina M. D. de; Van Keulen, Frederik; Ferreira, Bruno S.; Telo, João P.; Fonseca, M. Manuela R. da"Burkholderia sacchari DSM 17165 is able to grow and produce poly(3-hydroxybutyrate) both on hexoses and pentoses. In a previous study, wheat straw lignocellulosic hydrolysates (WSH) containing high C6 and C5 sugar concentrations were shown to be excellent carbon sources for P(3HB) production. Using a similar feeding strategy developed for P(3HB) production based on WSH, fedbatch cultures were developed aiming at the production of the copolymer P(3HB-co- 4HB) (poly(3-hydroxybutyrate-co-4-hydroxybutyrate)) by B. sacchari. The ability of this strain to synthesize P(3HB-co-4HB) was first shown in shake flasks using gammabutyrolactone (GBL) as precursor of the 4HB units. Fed-batch cultures using glucose as carbon source (control) and GBL were developed to achieve high copolymer productivities and 4HB incorporations. The attained P(3HBco- 4HB) productivity and 4HB molar % were 0.7 g/(L·h) and 4.7 molar %, respectively. The 4HB incorporation was improved to 6.3 and 11.8 molar % by addition of 2 g/L propionic and acetic acid, respectively. When WSH were used as carbon source under the same feeding conditions, the values achieved were 0.5 g/(L·h) and 5.0 molar %, respectively. Burkholderia sacchari, a strain able to produce biopolymers based on xylose-rich lignocellulosic hydrolysates, is for the first time reported to produce P(3HB-co-4HB) using gamma butyrolactone as precursor."