Determination of total sugars in lignocellulose hydrolysate by a mediated Gluconobacter oxydans biosensor Original Research Article

A microbial biosensor for sugar determination was prepared by surface modification of a graphite electrode using Gluconobacter oxydans cells. The sensitivity of amperometric detection was enhanced by using hexacyanoferrate(III) as a mediator. The G. oxydans cells contain membrane-bound aldose dehydrogenase, which catalyses the oxidation of wide range of sugars including all sugars present in lignocellulose hydrolysate. The substrate specificity of the biosensor, effect of pH, temperature, working potential, hexacyanoferrate(III) concentration as well as the physiological state of the cells for detection were carefully optimised. The upper value of the linear range of the optimised biosensor was in the range 1.1–2.2 g l−1 for determination of d-glucose, d-galactose, d-xylose, d-mannose and l-arabinose. The biosensor was used for total sugars determination during lignocellulose hydrolysate fermentation. A good correlation between total sugars determined in samples by the biosensor and by quantitative paper chromatography was obtained.