iBB

Xylonic acid (XA) is on the list of the 30 platform chemicals to be produced from biomass, as identified by the US Department of Energy.

The group of researchers Maryna Bondar, Teresa Cesário and Manuela Fonseca (iBB) was the first to report the capability of a bacterial species belonging to Safety Level 1, Paraburkholderia sacchari, at the time classified as Burkholderia sacchari, to produce large amounts of XA from xylose. XA is thermally stable and biocompatible, non-toxic, water soluble and non-corrosive, with properties similar to Gluconic Acid (GA). Its use in the pharmaceutical, food and chemical industries in general has been addressed with success.

While GA is produced from glucose, XA is obtained from xylose (sugar not used for human consumption). The invention relates to a biological process for XA production using xylose or lignocellulosic hydrolysates as substrate and a bacterial strain as biocatalyst. With this bioprocess, XA concentrations between 370 g/L and 390 g/L were obtained, corresponding to volumetric productivities from 4.8 g/(L.h) to 7.1 g/(L.h). The yield of XA on xylose ranged from 89% to 100%.

Paraburkholderia sacchari has the capacity to produce xylonic acid and xylitol, compounds ranked in the top 30 high-value chemicals from biomass. In a recent paper in Biochemical Engineering Journal, Maryna Bondar, Manuela Fonseca and Teresa Cesário from BERG-iBB reveal the outstanding ability of this bacterium to metabolize D-xylose to xylonic acid. D-xylonic acid is a five-carbon sugar acid that can replace gluconic acid in several applications. The biotechnological production of D-xylonic acid is advantageous over gluconic acid because it uses xylose as carbon source. Xylose is a very abundant sugar in nature and only few native bacterial strains can metabolize it. Fed-batch cultivations in a single bioreactor attained xylonic acid titers of 390 g L-1 and a productivity of 7.7 g L-1 h-1. This simplified process can significantly affect process economics, potentiating its translation to an industrial scale.

The organic fraction of municipal solid waste (OFMSW) accounts for approximately 30-40% of MSW in Europe. BERG-iBB researchers developed a process that uses this type of waste as a raw material or the production of the biodegradable biopolymer P(3HB). In a first step the complex carbohydrates in the waste are hydrolysed into simple monosaccharides. The hydrolysate is then used as a carbon source to feed and induce the bacterium Burkholderia sacchari to produce P(3HB). In order to overcome nutritional deficiencies and attain a significant polymer accumulation (58% g polymer/g CDW) the C/N ratio was adjusted and the hydrolysate was supplemented with minerals. This work demonstrates that an easily accessible waste can be transformed into valuable biodegradable bioplastics. The work was published in Bioresource Technology.

Photo details: municipal waste by OpenIDUser2, GFDL. 

Cassava (Manihot esculenta) cultivation is of great importance in many economies, particularly in Colombia. About 630,000 tons of C-rich cassava waste is produced annually and applications to high value products, applying the circular economy concept, must be developed. A recent publication in Journal of Polymers and the Environment assesses the potential use of cassava peel for the production of polyhydroxyalkanoates (PHAs) by Cupriavidus necator. A copolymer of P3HB-3HV was produced and processed into electrospun meshes of random and aligned microfibers, allowing the development of structures that can be applied in the context of tissue engineering. This work involved Manuela Fonseca, Frederico Ferreita and Teresa Cesário form BERG-IBB and has been done in collaboration with researchers from the University of Antioquia, Medellin-Colombia.

A biological process for the production of xylonic acid (XA) from xylose or from xylose-rich lignocellulosic hydrolysates has been patented by BERG-iBB researchers Teresa Cesário, Manuela Fonseca and Maryna Bondar (PT 115970). The ability of the wild strain Paraburkholderia sacchari (previously classified as Burkholderia sacchari) DSM 17165 to produce xylonic acid from renewable and sustainable feedstocks is claimed. XA is a potential substitute for gluconic acid (GA), namely in the pharma industry, as a chelating agent, as a precursor of 1,2,4-butanetriol, polyamides and polyesters, as well as in the production of solvents, paints, adhesives and dyes. Moreover, XA, like GA, can be used as a retardant of the setting time of cement paste. XA productivities in the range 4.8 g/(L.h) to 7.1 g/(L.h) and yields between 89% e 100% were achieved, with XA titres of 360 to 390 g/L, using one single, non-pressurised stirred tank reactor operating in the fed-batch mode under dissolved oxygen concentrations higher than 10%  saturation.