BIOCONVERSION OF WASTE BREAD TO GLUCOSE FRUCTOSE SYRUP AS A VALUE-ADDED PRODUCT

Bread is one of the most wasted products of all food in many countries around the world. Bread waste is a resource of carbohydrates, proteins and lipids which can be reused in order to get value-added products. In this study, bread residues were converted into a glucose syrup via two stage enzymatic hydrolysis. The optimization process and response surface methodology were used to find the optimal substrate, water and enzyme ratio to produce the highest yields of fermentable sugars. The effects of bread (11.34-28.66 g 100 g(-1)), a-amylase (0.013-0.047 KNU g(-1) bread) and glucoamylase (0.23-0.57 AGU g(-1) bread) loadings were investigated at liquefaction and saccharification stages. Results indicated that the amount of both enzymes was significant and determines the final glucose yield. Isomerization was performed for glucose conversion to fructose using optimal amounts of materials determined in hydrolysis experiments. Another optimization process was performed to determine the most effective amount of glucose isomerase enzyme (2.59-5.41 IGIU g(-1) syrup) and pH (6.79-8.21). The increase in enzyme loading and pH up to 8 accelerated isomerization reaction. With the optimal process parameters, the highest fructose yield was achieved (40.32%). Hydrolysis and isomerization processes show bread waste potential of being a resource for the bioproduction of higher value products.