A spectrophotometric method for quantitative determination of xylose in fermentation medium

Monitoring the consumption of sugars during fermentation is a key to optimizing product formation and maintaining a healthy environment for microorganisms. Difficulty arises in the availability of a rapid, inexpensive and sensitive method for the detection of sugars because fermentation media are a complex mix of nutrients, cell debris, waste and target products. A method involving reaction-based UV-Vis spectrophotometry for the quantitative determination of xylose as the target sugar was developed. Factors affecting xylose concentration measurements such as hydrochloric acid concentration, heating time and the amount of Fe³⁺ catalyst were investigated. A continuous scan revealed the working wavelength to be 671 nm. The effect of other components in the fermentation broth was found to be negligible. Absorbance shows a linear relationship with xylose concentration within a range of 0.1-0.5 g/L. Xylose concentrations from fermentation samples obtained at specific time intervals (0-168 h) were determined with the method and compared with YSI 2700, an enzyme electrode, HPLC-ELSD method, currently a common technique for measuring xylose and GC aldononitrile sugar derivatization method. Dilution is necessary for comparable xylose concentrations with YSI 2700 and HPLC-ELSD. Xylose concentration measurements obtained with the UV-Vis spectrophotometric method although quantitatively comparable to HPLC-ELSD xylose measurements were easily and conveniently obtained compared to YSI 2700, HPLC-ELSD and GC derivatization methods.