Browsing by Author "Almeida, M. Catarina M. D. de"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- A Burkholderia sacchari cell factory: production of poly-3-hydroxybutyrate, xylitol and xylonic acid from xylose-rich sugar mixturesPublication . 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."
- 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."
- Feeding strategies for tuning poly (3-hydroxybutyrate-co-4-hydroxybutyrate) monomeric composition and productivity using Burkholderia sacchariPublication . Raposo, Rodrigo S.; Almeida, M. Catarina M. D. de; Fonseca, M. M. R. da; Cesário, M. TeresaPoly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-4HB)) co-polymers were produced at bench-scale in fed-batch cultivations by Burkholderia sacchari from glucose (main carbon-source) and gamma-butyrolactone (GBL) as co-substrate. As P(3HB-4HB) properties highly depend on the 4-hydroxybutyrate (4HB) molar fraction, it is advantageous to have a thorough knowledge of the process in order to promote the production of the targeted final product. In this work, polymers with a 4HB molar percentage ranging from 1.5 to 8.4% (mol/mol) were obtained as consequence of a fine tuning of the fed-batch operation conditions, namely regarding the co-substrate feeding rate and its addition time, as GBL is toxic to B. sacchari cells. The best results regarding both the 4HB incorporation (molar%) and the co-polymer productivity (7.1% and 1.1g/(L.h) respectively) were reached when a pulse of GBL (<10g/L) was added early in the accumulation phase followed by a constant GBL addition at a rate similar to that of consumption so that a steady co-substrate concentration in the medium was maintained.
- 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."