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Marine algal carbohydrates as carbon sources for the production of biochemicals and biomaterials

Publication . Cesário, M. Teresa; Fonseca, M. Manuela R. da; Marques, Mafalda M.; Almeida, M. Catarina. M. D. de

The 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.

2018-05Journal article

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Feeding strategies for tuning poly (3-hydroxybutyrate-co-4-hydroxybutyrate) monomeric composition and productivity using Burkholderia sacchari

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

Poly(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.

2017-12Journal article

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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

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