Submitted to: Biosensors and Bioelectronics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 16, 1996
Publication Date: N/A
Interpretive Summary: Valuable sugars are chemically "locked up" inside low-value agricultural residues such as corn fiber (an abundant byproduct of wet-milling). Although processes are becoming available to recover these sugars, practical new technologies are needed to detect and monitor sugars in real-time under field and factory conditions. Currently available methods particularly suffer from slow response times, high maintenance and high cost. We found that biosensors (electronic instruments utilizing bacterial cells) were rugged and inexpensive to construct. Biosensors were reliable and simple to operate. Amperometric sensors (using a particular type of electronic interface) were superior to previously described potentiometric sensors, in that they were not affected by changes in pH. This work will be of interest to those developing new uses and value-added products from agricultural commodities and byproducts and will, in turn, benefit farmers by fostering new and expanded markets for their products.
Whole cells of Gluconobacter oxydans were employed in a microbial sensory for xylose determinations, using Clark-type electrodes. Bacterial cells were immobilized on chromatographic paper by simple physical adsorption and attached to the surface of the electrodes. The lower limit of xylose detection was approximately of 0.5 mM, and measurements were useful up to at least 20 mM xylose. Physiological buffers showed no effect on biosensor function. Responses were highly reproducible, showing a standard deviation of 6.7% over ten consecutive measurements. Whole-cell biosensors were relatively stable, retaining 60% of initial activity after 35 days of storage at 4 C. Xylose detection was not significantly affected by the presence of xylitol, suggesting that biosensors might be useful in monitoring conversions of these compounds. However, glucose or ethanol elicited a 10-fold higher response than xylose at equal concentrations (1 mM). Such interfering materials would need to be controlled or concurrently monitored in specific sensor applications.