Monday, April 30, 2007
5B-08

Enzymatic hydrolysis of wheat flour and soybean flour within a biorefinery concept

Ruohang Wang, Mehmet Melikoglu, Yu Ji, Apostolis Koutinas, and Colin Webb. School of Chemical Engineering and Analytical Science, The University of Manchester, Sackville Street, PO Box 88, Manchester, United Kingdom

This submission summarises the integrative application of the enzyme complexes from Aspergillus awamori and Aspergillus oryzae in wheat flour hydrolysis.  Temperature and pH optima of the glucoamylase from A. awamori and of the protease from A. oryzae were identified as 60°C, 4.5, and 55°C, 3.5, respectively.  In addition to hydrolysing gelatinised starch A. awamori glucoamylase also demonstrated the capability of hydrolysing raw starch.  Throughout a seven-day storage at 30°C the glucoamylase maintained 86.6% of its original activity.  When stored at 70°C, however, over 98% of the glucoamylase lost their activity in 55 mins.  An exponential decay model satisfactorily predicted the deactivation of A. awamori enzymes within a storage temperature range from 30°C to 70°C.  The parameters generated by this model indicated that this deactivation was largely a consequence of thermal rather than proteolytic effects.  When applied to hydrolyse a large volume of highly concentrated wheat flour suspension, heating to over 70°C for starch gelatinisation was most problematic because of the development into extremely high viscosity.  Improvement to heat transfer significantly shortened the heating process, reduced enzyme deactivation, and hence facilitated simultaneous starch gelatinisation and hydrolysis.  Near completion of starch hydrolysis was achievable at any temperature between 55°C to 70°C with proper addition of the A. awamori enzyme complex.  Protein hydrolysis, however, was much lower ranging from 13.9% at 55°C to barely detectable at 70°C.  Proportional addition of the enzyme complexes from both fungi into the same process raised protein hydrolysis up to 30% while maintaining starch hydrolysis above 95%.