54 Food and Beverage ADVERTISING SUPPLEMENT THE APPLICATION NOTEBOOK — September 2005 Determination of Cellobiose in Corn Stover Extract

Randy Benton, Metrohm-Peak, Inc

ellobiose is a disaccharide subunit of cellulose composed of C two glucose molecules linked in a (1→ 4) bond which can only be hydrolyzed by bacteria. Typically cellobiose is poorly 9000 digested in animals, including humans, with simple stomachs. How- ever, animals with complex stomachs, ruminants, have the bacteria 7000 required for cellobiose digestion. The detection and quantification of cellobiose is important in industries such as food and beverage and 5000 alternative energy research. The determination of cellobiose is of par- Response (nA) 3000 ticular interest in the food and beverage industry. If the raw sugar 1 2 3 5 6 that is to be added to a beverage, such as a fruit juice, is altered with 4 1000 the addition of cellobiose, the total sugar or brix will increase which will lower the actual sugar in the drink. In the alternative power 0 5 10 15 20 25 industry, cellobiose is hydrolyzed to produce ethanol to be used as an Time (min) alternative fuel. The efficiency of the hydrolysis can be determined by the residual cellobiose in the sample. Current techniques for the Figure 1: Stacked chromatogram of sample of corn stover extract and a determination of cellobiose include refractive index (RI), UV–vis standard. Peaks: 1 arabinose, 2 galactose, 3 glucose, 4 mannose, and in some cases conductivity. This method uses pulsed ampero- 5 xylose, 6 cellobiose. metric detection (PAD), which is a well accepted technique for the detection of sugars.

Experimental Conditions Conclusion A Metrohm Advanced Ion Chromatography system equipped with Using this method, the presence or absence of cellobiose can be a Metrohm Binary High Pressure gradient system, Metrohm 838 determined in less than 30 min, increasing the efficiency of current Advanced Autosampler, Metrohm 817 Bioscan Pulsed Amperomet- testing methods. The instrument used is simple, rugged, and very ric Detector, and an 830 IC interface was used for the analysis. Data reliable. There is no need for hazardous chemicals or their disposal. acquisition and processing were performed with Metrohm IC-Net This method also reduces the cost to the laboratory for purchasing 2.3 software. Bioscan temperature was controlled at 320 °C. The expensive instruments such as a mass spectrometer. Direct injection column employed for analysis was the Metrosep Carb1 (250 mm of the sample also increases the efficiency of the laboratory. Pulsed 4 mm). The Eluent used was A: 20 mM sodium hydroxide/ Amperometric Detection of carbohydrates is a well recognized and 2 mM sodium acetate and B: 50 mM sodium hydroxide / 50 mM useful tool in industries such as food and food additives, animal feed, sodium acetate at a flow rate of 1 mL/min. The injection volume was pharmaceutical, and others for the detection and quantification of 10 L. carbohydrates. This method would be especially useful for the detec- tion of adulterated maple syrup samples. Results and Discussion With the increasing cost of fuel and fuel production, alternative References fuel research is experiencing a resurgence of interest. The production (1) “Metrohm Application Works AW-US6-0109-062005,” Metrohm-Peak, of ethanol from biomass is on the cutting edge of such research. As Inc. (Housten, Texas). a result of this, a simple yet rugged method is needed to determine the efficiency of the hydrolysis. If the hydrolysis is complete no cel- lobiose peak is expected and in fact none is seen in this extract. For this study, samples of corn stover were pulped. The pulp underwent the process for ethanol production and the extract injected directly Metrohm-Peak, Inc. into the instrument. Figure 1 is a stacked chromatogram of the corn 12521 Gulf Freeway, Houston, TX 77034 stover extract (red trace) and a standard chromatogram (black trace). tel. (800) 410-7118, fax (281) 484-5001 [email protected], www.metrohm-peak.com For More Information Circle 43