The use of corn cob as an excellent starting material for obtaining XOS and fungal enzymes involved in their production

Abstract

Corn is widely used in the diet all over the world which generate corn cob as one of the most common agrowaste material. Corn cob mainly consists of lignocellulose with a high quantity of xylan; therefore, it can be considered the main source for xylooligosaccharides (XOS) production. XOS are prebiotic, functional food ingredients, which stand out on the market of oligosaccharide prebiotics because of their properties (antitumor effect, immunomodulatory effect, antioxidant power, and high pH and thermal stability). The European Commission has approved XOS produced from corn cob as safe for human consumption. For XOS production highly efficient xylanase obtained by Aspergillus tubingensis FAT35 under SSF on corn cob medium was used. Three methods of XOS production were evaluated: by hydrolysis of xylan alkali isolated from corn cob, by direct hydrolysis of xylan in corn cob and simultaneously production during fungal growth on corn cob (in situ). XOS were separated by ethanol precipitation from corn cob hydrolysate and from fermentation extract. In this way, the enzyme is concentrated in the precipitate, and XOS (remaining in the supernatant) are partially purified (separated from unhydrolyzed xylan and long chain oligomers). All prepared XOS were characterized by TLC and HPLC and antioxidant potential. Thanks to the high antioxidant potential (proven by DPPH, ABTS, FRAP, and ORAC tests) obtained XOS are good candidates for a functional food additive. Although the highest yield of XOS was obtained by the standard method (enzymatic hydrolysis of isolated xylan), additional methods represent the direct use of agro-waste material in an environmentally and economically suitable way. Special attention attracts in situ production because after isolation of XOS by ethanol precipitation the enzyme remains functional active and available for further use in next process.