THE EXTRACTION OF A GLUCOMANNAN POLYSACCHARIDE FROM KONJAC CORMS (ELEPHANT YAM, AMORPHOPHALLUS-RIVIERII)

A process for the micropropagation of Amorphophallus rivierii (elephan t yam or konjac) and for the extraction and purification of the glucom annan polysaccharide from fresh konjac plant corms has been developed. This process involves extraction with 2-propanol. which has the addit ional benefit of extracting carotenoids as a potentially valuable side -product. Starch granules with an unusually high and homogeneous gelat inisation temperature range are normally present in the corms, particu larly immature ones, and this greatly reduces the strength of gels for med using the glucomannan. Therefore, the extraction process also invo lves the selective hydrolysis of the starch, by alpha- and beta-amylas es that have been specially selected for an absence of contaminating b eta-mannanase or beta-glucanase activity that would depolymerise the g lucomannan and render it nonfunctional. Bacillus lichenformis alpha-am ylase was preferred. Using this process pure glucomannan could be extr acted which, when mixed with kappa-carrageenan, forms a gel almost twi ce as strong as locust bean gum-kappa-carrageenan gels of the same con centration.