Enzymatic hydrolysis optimization of bread waste into syrup

The literature review deals with the status and the causes of bread waste all over the world. More importantly, the current managements of increasing bread waste. Enzymatic hydrolysis by α-amylase and amyloglucosidase is a potential treatment, which transforms bread waste into syrups for further revaluation with functional compounds. The aim of the experimental work was to determine the influence of enzymatic hydrolysis conditions (hydrolysis time, hydrolysis temperature, enzyme dosage of α-amylase and amyloglucosidase) on glucose content and free amino nitrogen (FAN) content of resulting hydrolysate from bread waste. Furthermore, the effect of lactic acid fermentation on glucose content was studied when bread waste was subjected to simultaneous hydrolysis and fermentation with Pediococcusclaussenii (E-032355T). Glucose content varied greatly under different hydrolysis conditions from nearly 17% to only 5%, while FAN content was barely influenced. pH value had slight changes and no Bacillus cereus bacteria was found. A well fitted model for glucose content was obtained with an excellent power of interpretation, prediction and optimization. Enzyme dosage was the principal factor having a significant effect on hydrolysis efficiency, followed by temperature and time. With optimized hydrolysis conditions (50 mg/kg α-amylase and 2500 mg/kg amyloglucosidase, 30℃, 19 hours), the glucose content 16.31% was achieved, and the result was in accordance with the value 16.39% predicted by the model. Moreover, a 2.2% increase of glucose yield was detected when waste bread was subjected to simultaneous hydrolysis and fermentation compared to the control sample (bread waste was treated only with hydrolysis under the same condition). The well growth of used lactic acid bacteria (LAB) strains Pediococcusclaussenii (E-032355T) resulted in lower pH, which further improved enzymes activities and increased glucose content of the hydrolysate.