Intermediate-Scale, Semicontinuous Solid-Phase Fermentation Process for Production of Fuel Ethanol from Sweet Sorghum

Abstract

A novel, semicontinuous solid-phase fermentation system was used to produce fuel ethanol from sweet sorghum. The process was at an intermediate scale. In the process, dried and shredded sweet sorghum was rehydrated to 70% moisture, acidified to pH 2.0 to 3.0, and either pasteurized (12 h at 70 to 80°C) or not pasteurized before spray inoculation with a broth culture of Saccharomyces cerevisiae. Fermented pulp exited the semicontinuous fermentor after a retention time of 72 h and contained approximately 6% (vol/vol) ethanol. Ethanol yields from dry sweet sorghum were 176 to 179 liters/10 3 kg (85% of theoretical). Production costs for a greatly scaled-up (×1,400) conceptual version of this system were projected by calculation to average $0.47/liter for 95% ethanol. The calculated energy balance (energy output/energy input ratio) was estimated to be 1.05 when pasteurization was included and 1.31 when pasteurization was omitted. In calculating the energy balances, the output energy of the protein feed byproduct and the input energy for growing the sweet sorghum were not considered. A design for the scaled-up plant (farm scale) is provided.

Fundamental Study of Kitchen Refuse Utilization for Ethanol Fermentation by <I>Saccharomyces cerevisiae</I>

“…Identical results were obtained when ethanol fermentation from beet molasses [18] and soy bean pulp hemi cellulose was conducted [19]. Extensive research on non-sterilized ethanol fermentation from renewable resources such as sweet sorghum [21], beet molasses [22] and cane molasses [23] has been intensively pursued in view of reducing the ethanol production cost. About 30-40% of the processing energy consumption can be saved by employing non-sterilized fermentation [24] .…”

Simultaneous Solid Phase Fermentation and Saccharification of Cassava Fibrous Residue for Production of Ethanol

“…These problems could be successfully overcome by employing appropriate strategies. Other workers have used an auger type bioreactors [9,11], rotary drum fermentor [12] and static fermentors with periodic agitation of fermenting mass [13,14], as well as inert gas circulation [19] to overcome these problems in fermentation of pulpy substrates.…”

Increasing Ethanol Titer and Reducing Enzyme Dosage via Fed-Batch, Simultaneous Saccharification and Fermentation in a High Solids Bioreactor

“…There are many advantages of using a solid state fermentation system: lower production cost, less energy needed, and greater fermentation productivity [9]. Gibbons et al [10,11] used solid state fermentation to convert sweet sorghum and fodder beet pulp to ethanol achieving ethanol yields of 85% and 78-85% of theoretical, respectively. Moukamnerd et al [9] used a solid state fermentation system to convert raw corn starch to ethanol.…”