Simultaneous dark fermentative hydrogen and ethanol production from waste bread in a mixed packed tank reactor (MPTR) was investigated. Waste bread was first hydrolyzed by the produced enzymes to generate the waste bread hydrolysate which was subsequently introduced to the MPTR for dark fermentative hydrogen and ethanol production. The optimal hydrogen and ethanol production rates were 15.01 mmol/(h•L) and 23.25 mmol/(h•L) when the organic loading rate reached 32 g/(L•d). The unit hydrogen and ethanol production were 4.87 mmol hydrogen/g waste bread and 7.54 mmol ethanol/g waste bread, respectively. This study provided a new direction for economic and efficient hydrogen and ethanol production from waste bread.

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Waste pastry (6%, w/v) was hydrolyzed by the produced glucoamylase and protease to obtain the glucose (19.8g/L) and free amino nitrogen (179mg/L) solution. Then, the effect of organic loading rate (OLR) (8-40kgCOD/(md)) on dark fermentative hydrogen production in the continuous stirred tank reactor (CSTR) and continuous mixed immobilized sludge reactor (CMISR) from waste pastry hydrolysate was investigated and compared. The maximum hydrogen production rate of CSTR (277.76mL/(hL)) and CMISR (320.2mL/(hL)) were achieved at OLR of 24kgCOD/(md) and 32kgCOD/(md), respectively. Carbon recovery ranged from 75.2-84.1% in the CSTR and CMISR with the balance assumed to be converted to biomass. One gram waste pastry could produce 0.33g (1.83mmol) glucose which could be further converted to 79.24mL (3.54mmol) hydrogen in the CMISR or 91.66mL (4.09mmol) hydrogen in the CSTR. This is the first study which reports dark fermentative hydrogen production from waste pastry.