Air-dried sweet sorghum stalk for long-term storage and ethanol fermentation

The air-dried sweet sorghum stalk was employed for a long-term storage to prolong the raw material supply for ethanol production. The change of sugar content in the stalk was investigated in the drying and the storage process, respectively. Results indicated that the total sugar loss during the drying process was 4.58%, when the moisture of fresh stalk decreased from 80% to 18%. In the subsequent 6 months storage duration, the total sugar and reducing sugar in the dried stalk almost kept no obvious decrease when the stalk moisture was lower than 22%. The ‘safe moisture’ for dried sweet sorghum long-term storage could be thereby regarded as 22%. After 6 months storage, the dried stalk was rehydrated for fermentation to check the fermentability. Results showed fermentation could be rapidly completed in 24 h and ethanol concentration in substrate could reach 67.06 mg/g (wet basis). There were no obvious inhibitions in the fermentation process. According to the results above, it was an effective way to store sweet sorghum stalk for a long time by air-drying stalk. This work could give a potential solution to the shortage of raw material supply in the year-round ethanol production from sweet sorghum stalk.