Research on Solid-State Ethanol Fermentation Using Dry Sweet Sorghum Stalk Particles with Active Dry Yeast

An effective method of sweet sorghum stalk storage in dry particles for 8 months was reported in this study. Meanwhile, the experiments of solid-state fermentation (SSF) for ethanol using dry sweet sorghum stalk particles (DSSSPs) with active dry yeast were carried out to clarify the effects of different variables, including temperature, particle size, yeast inoculation rate, and water content on yeast growth, CO2 and ethanol formation, and sugar use. The results indicated that the effects of temperature and particle size on yeast growth and ethanol yield were significant. In addition, the yeast inoculation rate and water content were greatly related to yeast growth, even though they had less significant effects on ethanol yield. The suitable ranges of temperature and particle size for yeast growth were 25-30 degrees C and 1.6-2.5 mm, respectively, in which higher values of Y-cell/sugar of 0.2681 and 0.3538 mg mg(-1) were obtained. The suitable ranges for ethanol production were 35-40 degrees C and 0.9-1.6 mm, in which higher values of Y-ethanol/sugar of 0.2404 and 0,2702 mg mg(-1) could be obtained. The adequate yeast inoculation rate should be 0.250, and higher values of Y-ethanol/susugar and Y-cell/sugar could be up to 0.2486 and 0,3017 mg mg(-1), respectively. In addition, the suitable water content for ethanol production and yeast growth was 76.47%. With this water content, the Yethanol/sugar and Y-cell/sugar could reach 0.2593 and 0.4211 mg mg(-1), respectively.