Simple and robust monitoring of ethanol fermentations by capillary electrophoresis

Abstract

Free-solution capillary electrophoresis (CE), or capillary zone electrophoresis, with direct UV detection was used for the first time for the determination of mono- and disaccharides, sugar alcohols, and ethanol in fermentation broths. Sample preparation proved to be minimal: no derivatization or specific sample purification was needed. The CE conditions can be adapted to the type of fermentation by simply altering the background electrolyte (BGE). KOH (130 mM) or NaOH (130 mM) as the BGE led to the fastest analysis time when monitoring simple fermentations. A mixture of 65 mM NaOH and 65 mM LiOH led to a 19% improvement in resolution for a complex mixture of carbohydrates. Quantification of a simple carbohydrate fermentation by CE showed values in close agreement with that of high-performance anion exchange chromatography and high-performance liquid chromatography (HPLC) on a cation exchange resin. For complex fermentations, quantification of carbohydrates by HPLC and CE led to similar results, whereas CE requires an injection volume of only 10-20 nL. Analysis of an ethanol fermentation of hydrolyzed plant fiber demonstrated the robustness of the separation and detection of carbohydrates, as well as ethanol. Ethanol determination is achieved by coupling the CE method to pressure mobilization, using the same instrument and the same sample.

Recent advances in the application of capillary electromigration methods for food analysis and Foodomics

“…Thus, 130 mM NaOH resulted in the best resolution among single‐salt BGEs, whereas a mixture of 65 mM LiOH and 65 mM NaOH not only increased the resolution but also increased the analysis time. The interest of this method lies in its ability to monitor ethanol and carbohydrates on the same instrument to provide a complete picture of the fermentation sample . A similar method like the one previously described was used for the quantification of carbohydrates in breakfast cereals in order to monitor sugar levels because their influence on the high prevalence rates of obesity and other diet‐related diseases.…”

Investigation of photochemical reaction products of glucose formed during direct UV detection in CE

“…By now, the phenomenon is ascribed to a fast base catalyzed photochemical reaction in the detection window of the separation capillary resulting in the formation of substances that exhibit UV absorption in the mentioned region . The applicability of this novel method of saccharide detection in CE has been demonstrated in various matrices . Other investigations dealt with the underlying photochemical reaction itself .…”

Separation and Characterization of Synthetic Polyelectrolytes and Polysaccharides with Capillary Electrophoresis

“…The detection of the CE was found to have a limit of detection 10-100x better than HPLC and a better selectivity of detection. Direct detection in CE is not as sensitive as more convoluted methods based on derivatization or pulsed-amperometric detection in ionchromatography [36]. The method will thus need further improvement to be used for trace detection.…”

“…In the equation, ep is electrophoretic mobility, is voltage, is the length to the detector, is the total length of the capillary, is the time of migration, and is the migration of a neutral species. Using electrophoretic mobility (thus correcting for EOF variations) allows easy visual comparison of results, for example, to allow identification of trace sugars in ethanol fermentation [36].…”