Solid-state fermentation as a tool for methylxanthine reduction and simultaneous xylanase production in cocoa meal

Abstract

Cocoa meal, the residue from cocoa processing, when used in animal feed can negatively affect health and performance because of the high concentrations of methylxanthines (theobromine and caffeine) and high fiber content. Solid-state fermentation (SSF) is one method to increase the use and value of the residue and to remove undesirable compounds. The fungus Aspergillus awamori IOC-3914 used in SSF was able to grow in cocoa meal, reduce methylxanthines and produce xylanase. Enzyme production reached about 66.5 U/g in 48 h before and 72 U/g after optimization. The xylanase showed good thermal stability, with residual activity between 97% and 90% after 4 h of incubation between 30 and 40 °C. The highest residual activity was obtained at pHs between 5.0 and 6.0. Aspergillus awamori reduced the theobromine and caffeine contents by about 69% and 63%, respectively, after the optimization process. Addition of feather meal significantly increased the reduction of methylxanthines. SSF in cocoa meal using A. awamori can expand the options for waste use, by producing enzymes and reducing the contents of undesirable caffeine and theobromine.