Nutritional enhancement of cereal milling wastes using enzymes

Wheatfeed is a low value by-product of the cereal milling industry and has potential as an ingredient of pet foods. However, it has a high fibre content and this renders it unsuitable for non-ruminants unless some means can be found to convert the fibre to more digestible substances. This work considers enzyme hydrolysis as a means for improving the nutritional value of wheatfeed. Preliminary investigations focused on evaluating mixtures of enzymes in various combinations. The extent of hydrolysis was routinely assayed by measuring the release of sugars and proteins. Further experiments were performed to establish the optimal conditions under which a mixture of enzymes, comprising cellulase, hemicellulase and pectinase, hydrolysed wheatfeed. Studies were also conducted where these enzymes were added sequentially to wheatfeed and useful information was gained on the composition of the susceptible components. Steam explosion was investigated as a pretreatment of wheatfeed to make subsequent enzyme treatment more effective. However, the results were inconclusive. Trials were carried out using commercially available enzymes to compare their effectiveness on the wheatfeed. A cellulase, was selected for further investigation into the effects of particle size, extent of agitation, and enzyme concentration on sugar release. An empirical mathematical model describing the action of this enzyme was developed. Enzyme treatment of wheatfeed was also performed under conditions of reduced water content, or 'solid state'. However, enzyme action was limited, yielding lower quantities of sugars and protein. The treatment of wheatfeed with enzymes was shown to increase digestibility of the substrate. However, the high costs of enzymes would effectively rule this out as a commercial option and alternative methods such as for example a form of composting using cellulolytic fungi might prove more economic.