Submitted to: Process Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 1999
Publication Date: N/A
Interpretive Summary: The fuel ethanol industry has become an important partner with American agriculture, but ethanol still has difficulty competing economically with imported petroleum. In order to offset the relatively high cost of ethanol production, we sought to identify new markets for value- added coproducts from fuel ethanol production. Corn fiber is an abundant byproduct of fuel ethanol production from wet-milled corn, currently used as a component of low-value animal feeds. We developed a novel fermentation process to produce the valuable sugar substitute, xylitol, from a mixture of sugars derived from corn fiber. Results should be of value to fuel ethanol producers who are looking for new coproduct markets to enhance the economic competitiveness of their industry. Enhanced production of ethanol should in turn benefit farmers by providing expanded markets for corn products.
Technical Abstract: Pichia guilliermondii strains NRRL Y-12723 fermented mixtures of xylose and arabinose to form xylitol and arabitol. However, cultures grown on a mixture of glucose, xylose, and arabinose, in ratios characteristic of corn fiber hydrolysates, preferentially utilized glucose and only slowly metabolized pentose sugars with low yields of sugar alcohols. We, consequently, developed a two-stage, sequential fermentation scheme for production of xylitol and arabitol from a mixture of sugars. Following glucose consumption, cells were removed from mixed sugar cultures and replaced with cells from cultures grown on xylose alone. In the second fermentation stage, xylose and arabinose were successfully fermented to xylitol and arabitol. Dilute acid hydrolysates of corn fiber were suitable substrates for the two-stage fermentation process but only after treatment with a mixed-bed deionization resin.