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During ethanol production, the ratio of various sources of starch-hydrolyzing enzymes significantly influences hydrolysis efficiency in a very high gravity (VHG) system. In this study, the enzyme matching approach was proposed to optimize liquefaction and saccharification yield of cassava root and cassava starch. For fresh cassava root, the synergistic effect of using Techzyme Q-Add enzyme (93 °C pH 5.6) for liquefaction and GC 147 enzyme (61.5 °C pH 4.2) for saccharification achieved the highest yield among all enzyme-matching designs. At 25% solid, highest total reducing sugar (TRS) yields from sequential liquefaction and saccharification of cassava starch, fresh cassava, and dry cassava were 87.9%, 85.1%, and 70.0% corresponding to 286.8, 249.4, and 241.1 g/L, respectively. For VHG ethanol fermentation by Saccharomyces cerevisiae TISTR 5606, separate liquefaction and simultaneous saccharification and fermentation (SLSSF) gave a significantly higher ethanol concentration compared with separate liquefaction and saccharification and fermentation (SLSF). From a 35% solid SLSSF system, the highest ethanol produced at 30 °C was 27.3 g/L from 72 h, respectively. The results suggested that SLSSF could effectively shorten the time course of the whole process for liquefaction, saccharification, and fermentation from 74 h to only 26 h for similar ethanol production yields. [ABSTRACT FROM AUTHOR]

Methane and ethanol were co-produced from different feedstock, including a mixture of dairy manure and soybean straw (DMS), a mixture of pig manure and soybean straw (PMS), and soybean straw alone (SS), after anaerobic digestion times of 30 and 60 days in mesophilic conditions. Digesting DMS for 60 days led to the highest methane yield of 115.3 g/kg dry raw feed; however, the lowest ethanol yield of 88 g/kg dry raw feed was observed. After 30 days, SS yielded the lowest methane levels (45.2 g/kg dry raw feed) but the highest ethanol levels (113.5 g/kg dry raw feed). Analysis of the net energy balance showed that the highest net energy balance, 6549 kJ/kg of dry raw feedstock, was achieved from the digestion of DMS for 60 days. Overall, both the type of feedstock and length of digestion time played important roles in the integrated processing of methane and ethanol from livestock manure and straw. [ABSTRACT FROM AUTHOR]

Methane and ethanol were co-produced from different feedstock, including a mixture of dairy manure and soybean straw (DMS), a mixture of pig manure and soybean straw (PMS), and soybean straw alone (SS), after anaerobic digestion times of 30 and 60 days in mesophilic conditions. Digesting DMS for 60 days led to the highest methane yield of 115.3 g/kg dry raw feed; however, the lowest ethanol yield of 88 g/kg dry raw feed was observed. After 30 days, SS yielded the lowest methane levels (45.2 g/kg dry raw feed) but the highest ethanol levels (113.5 g/kg dry raw feed). Analysis of the net energy balance showed that the highest net energy balance, 6549 kJ/kg of dry raw feedstock, was achieved from the digestion of DMS for 60 days. Overall, both the type of feedstock and length of digestion time played important roles in the integrated processing of methane and ethanol from livestock manure and straw. [ABSTRACT FROM AUTHOR]