Starch Depolymerization with Diluted Phosphoric Acid and Application of the Hydrolysate in Astaxanthin Fermentation

• Main Authors: David Alexander Mitchell, Oscar E. Molina, Anabella Gaitan, Tânia M.B. Bonfim, Juliana Adelmann, Adelia Grzybowski, Maurício Passos, José Domingos Fontana
• Format: Article
• Language: English
• Published: University of Zagreb 2008-01-01
• Series: Food Technology and Biotechnology
• Subjects: cassava starch; phosphorolysis; acid hydrolysis; depolymerization; phosphoric acid; astaxanthin
• Online Access: http://hrcak.srce.hr/file/41733

An innovative alternative for cassava starch hydrolysis has been developed using diluted (about 0.1 %) phosphoric acid at 160 °C. This technology is advantageous for developing countries where enzyme costs are prohibitive and hydrochloric acid is currently the only catalyst used for starch depolymerization. Lower concentrations of the byproduct hydroxymethyl furfural (HMF) were generated during starch hydrolysis when using phosphoric acid as compared to hydrochloric acid at any given acidic pH. Glucose was the major product from phosphorolysed starch under most reaction conditions, although maltosaccharides with degrees of polymerization from 2 to 7 were also produced, with their relative amounts depending on hydrolysis conditions. Neutralization of the acid with aqueous ammonia produced a hydrolysate with sources of C (free sugars), P (phosphate), and N (ammonium) that could find several applications. We demonstrated one of these, namely the potential for the use of the hydrolysate as a fermentation feedstock, by cultivating the astaxanthin-producing red yeast Xanthophyllomyces dendrorhous on it. Cassava wastewater, a polluting byproduct of starch processing, was found to be a convenient source of nitrogen for this fermentation process.