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%.

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.

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.