In this study, expired and/or returned chocolate products, mainly, couverture chocolate and chocolate sauce were used as substrates for bioethanol production. Box-Benkhen experimental design was employed for the determination of optimum conditions for bioethanol production. The use of both chocolate products as substrates with 20% (w/v) loading without any enzymatic or chemical pretreatment and any addition of nutrients revealed that highest bioethanol yield coefficient Y-PS= 0.50 was obtained based on sugar consumption with chocolate sauce under optimum conditions where 10% (v/v) of inoculum ratio was used, pH 5.50 for 3 days of incubation. On the other hand, the highest bioethanol productivity achieved was 1.13 g/L/h with couverture chocolate where inoculum ratio was 6% (v/v), pH 5.25 for one day of incubation. These results showed that chocolate products could use as effective, economic alternative substrates for bioethanol production
