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Abstract
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The global push for renewable energy has spurred research into bioethanol, a renewable fuel source that also reduces air pollution. A significant source of potential feedstock is the substantial amount of bread waste generated annually: over 100 million tons of wheat bread are produced globally, with 7-10% becoming waste. This study explored using this waste to produce bioethanol with Zymomonas mobilis. The process was conducted in two key steps. First, enzymatic hydrolysis using α-amylase and amyloglucosidase yielded a maximum reducing sugar concentration of 141 g/l. Second, fermentation was optimized using response surface methodology (RSM) by manipulating four factors: initial sugar concentration (85 g/l), bacterial dry weight (0.0325 g), peptone weight (0.36 g), and fermentation time (27 h). These conditions resulted in a maximum ethanol production of 31.4 g/l. This represents an 80.83% sugar consumption and an ethanol yield of 0.457. This efficient bioethanol production from waste bread using Zymomonas mobilis demonstrates the potential for sustainable fuel generation and waste reduction.
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