Scientists look for prebiotics from corn cobs

Using a technique called autohydrolysis, non-digestible oligosaccharides were released from the corn cob with prebiotic activity, which might be of relevance for the design of future symbiotic preparations.

"With the present work it was shown that autohydrolysis constitutes a promising approach for the production of oligosaccharides from corn cobs capable of supporting the growth of Bifidobacterium adolescentis in comparison to commercial xylo-oligosaccharides," wrote lead author Patricia Moura in the journal LWT - Food Science and Technology .

Prebiotic ingredients, or those that boost the growth of beneficial probiotic bacteria in the gut, are worth about €90 million in the European marketplace but are forecast to reach €179.7 million by 2010, according to Frost & Sullivan.

The market has been largely created by three inulin producers, all based in Europe, but other ingredient manufacturers are increasingly looking to promote the prebiotic effect of their products as evidence suggests that prebiotics could be even more useful than the probiotic bacteria that they feed.

Prebiotics, which are derived from insoluble fibres and oligosaccharides, can be incorporated into a wider variety of end products than probiotic bacteria.

They have also benefited from the promotional efforts of probiotic suppliers, who have significantly raised public awareness of gut health in recent years.

The researchers, from Lisbon's National Institute of Engineering and the Higher Institute of Agriculture, degraded hemicellulose in the corn to selective release soluble oligomeric structures xylo-oligosaccharides (XOS).

The prebiotic activity of two fractions with average degrees of polymerization (DP) of 3-4 and 5-6 were compared with commercial XOS (Xylo-Oligo95P, Suntory, Japan).

Moura and co-workers then tested the ability of these oligosaccharides (mainly xylotriose and xylotetraose) to promote the growth of selected gut bacteria, including Bifidobacterium adolescentis , B. longum , Lactobacillus brevis and L. fermentum .

It was found that B. adolescentis and L. brevis displayed the highest growth and XOS consumption, while growth of B. longum and L. fermentum was low.

"As prebiotic candidates, further in vitro and in vivo fermentation studies of corn cob xylo-oligosaccharides by intestinal microbiota would be required to investigate about their capability to exert a selective stimulation over the growth of beneficial bacterial groups in the intestinal ecosystem," wrote the authors.

"One example of an interesting approach for future work would consist on the calculation of the prebiotic index (PI) of the xylo-oligosaccharides from autohydrolysis.

It would permit a quantitative description of the prebiotic effect of corn cob xylo-oligosaccharides considering other common intestinal bacterial groups besides bifidobacteria and lactobacilli, and simultaneously provide for a comparative score between different oligosaccharides," they added.

"The different XOS utilization patterns observed among the tested strains might be of relevance for the design of future species-specific prebiotic non-digestible oligosaccharides NDOs and symbiotic preparations," concluded the researchers.

Source: LWT - Food Science and Technology (Elsevier) Volume 40, Issue 6, August 2007, Pages 963-972 "In vitro fermentation of xylo-oligosaccharides from corn cobs autohydrolysis by Bifidobacterium and Lactobacillus strains" Authors: P. Moura, R. Barata, F. Carvalheiro, F. Girio, M.C. Loureiro-Dias and M.P. Esteves