Abstract
In this study, waste breads have been utilized as the only nutrient source for the production of glucose using Aspergillus niger and subsequently ethanol production from glucose by Saccharomyces cerevisiae. Solid-state fermentation of waste bread by Aspergillus niger resulted in the production of a multienzyme solution containing amylolytic and proteolytic enzymes. The glucoamylase and protease enzymes are then extracted, and enzyme activities were quantified. This crude enzyme extract was used for the hydrolysis of waste bread at 55 °C at 300 rpm. After hydrolysis, the amount of glucose was determined using anthrone colorimetric method, and the free amino nitrogen (FAN) was determined by ninhydrin colorimetric method. The resulting solution contains approximately 145 g/l of glucose. The bread hydrolysate was then further used to produce ethanol having concentration of 54 ± 2 g/l. The result depicts yield of ethanol from glucose, YP/S, as 0.37, i.e., a conversion efficiency of 72%. This process is important in the sustainable chemical industry because it converts the waste food into a value-added product like ethanol.