2-Phenylethanol biooxidation by Gluconobacter oxydans: influence of cultivation conditions on biomass production and biocatalytic activity of cells

Gluconobacter oxydans can be used as a whole-cell biocatalyst in many industrial processes focused on production of carbonyl and carboxylic compounds by oxidation of respective alcohols. However, high biocatalyst production costs limit its widespread industrial application. Therefore, the influence of Gluconobacter oxydans cultivation conditions on cell growth and the activity in biooxidation of 2-phenylethanol to phenylacetaldehyde and phenylacetic acid was investigated using batch and fed-batch cultivation cultures. The maximum total activity (given by the product of specific activity of cells and biomass concentration) was obtained by batch cultivation in a medium containing 25 g/L glycerol, at pH 4.5 and 20% oxygen saturation. In a fed-batch culture the best biomass growth was obtained with the feeding medium containing 125 g/L glycerol at a flow rate of 0.02 L/h per 0.5 L of starting culture volume. Although the final biomass concentration was around two times higher, the specific biotransformation activity of cells was only around 20% compared to the biocatalyst prepared by batch culture.