Submitted to: Corn Utilization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 29, 1998
Publication Date: N/A
Technical Abstract: Corn fiber is an abundant, coproduct of wet-milling, currently used as a component of the relatively low value animal feed, corn gluten feed. Corn fiber can be hydrolyzed to produce a mixture of sugars, including glucose, xylose and arabinose. Xylose can be reduced to form xylitol, valued as a natural sweetener. Although xylitol has been conventionally produced by hydrogenation of xylose from wood fiber, fermentation of xylose from corn fiber may be an attractive alternative. Certain yeasts, such as Pichia guilliermondii, efficiently convert xylose to xylitol. However, this fermentation will not proceed in the presence of glucose. Instead, cultures preferentially utilize glucose, and only slowly metabolize xylose and arabinose, with low yields of xylitol and arabitol. To circumvent this problem, we developed a two-stage fermentation for production of xylitol from mixed sugars. In the first stage, glucose was consumed by growing cells of P. guilliermondii. During the diauxic lag phase following glucose exhaustion, cells were removed from the fermentation and replaced with fresh cells produced on xylose. In the second fermentation stage, the remaining xylose and arabinose were converted to xylitol and arabitol. Mild acid hydrolysates of corn fiber proved to be suitable substrates for this process, after fermentation inhibitors were removed by deionization.