Rye, triticale, and barley were evaluated as starch feedstock to replace wheat for ethanol production. Preprocessing of grain
by abrasion on a Satake mill reduced fiber and increased starch concentrations in feedstock for fermentations. Higher concentrations
of starch in flours from preprocessed cereal grains would increase plant throughput by 8–23% since more starch is processed
in the same weight of feedstock. Increased concentrations of starch for fermentation resulted in higher concentrations of
ethanol in beer. Energy requirements to produce one L of ethanol from preprocessed grains were reduced, the natural gas by
3.5–11.4%, whereas power consumption was reduced by 5.2–15.6%. 相似文献
Very-high-gravity (VHG) rye and triticale mashes, containing about 28.5 g dissolved solids/100 mL of mash supernatant, were
prepared by adjusting water:grain ratios to 2:1. Because of high viscosity, which develops during mashing, it was necessary
to pretreat ground rye-water slurries with viscosity-reducing enzymes. There were no viscosity problems during the preparation
of triticale mashes. Fermentations were conducted at 20°C, with and without 16 mM urea as a nitrogenous supplement. All fermentations
were completed within 120–144 h. Supplementation with urea shortened the times required for completion of fermentation by
33% for triticale and by 40% for rye. The fermentation efficiencies for both grains ranged between 90 and 93%. These values
are comparable to those reported for wheat, implying competitiveness of rye and triticale as fermentation feedstocks to replace
wheat. The final ethanol yields were 409 L for rye and 417–435 L for triticale/t (dry basis). For a given size of fermentation
vessel, 33% more grain was used in the VHG fermentation process than in normal gravity fermentation. This resulted in a 35–56%
increase in ethanol concentration in the beer, when fermentors were filled to a constant volume. The corresponding reduction
in water use by about one-third would result in savings in energy consumption in mash heating, mash cooling, and ethanol distillation.
Fermentation efficiencies and final ethanol yields obtained per unit weight of grain fermented were not significantly different
from the normal gravity fermentations. 相似文献
Very high gravity (VHG) wheat mashes containing more than 300 g of dissolved solids per liter were prepared and fermented
with active dry yeast at 20, 25, 30, and 35°C with and without yeast extract as nutrient supplement. At 20°C, mashes with
38% (w/v) dissolved solids end-fermented without any nutrient supplementation and maximum ethanol yields of 23.8% (v/v) were
obtained. With increasing temperatures, the sugar consumption decreased. Addition of yeast extract stimulated the rate of
fermentation at all temperatures, but did not increase the total amount of sugar consumed. The stimulatory effect of yeast
extract on cell multiplication decreased with increasing sugar concentration, and virtually no difference in cell number was
observed between yeast extract-supplemented and unsupplemented mashes at sugar concentrations above 33% (w/v). The fermentative
capacity of the yeast (expressed as maximum specific rate of sugar consumption) remained the same at all sugar concentrations
in unsupplemented mashes, but decreased in yeast extract-supplemented mashes at sugar concentrations below 33% (w/v). When
the sugar concentration was above 33% sugar (w/v), the fermentative capacity in yeast extract-supplemented mashes was greater
than that observed in unsupplemented samples. 相似文献
Distance fingerprinting : Pulsed electron–electron double resonance spectroscopy (PELDOR) is applied to the octameric membrane protein complex Wza of E. coli. The data yielded a detailed distance fingerprint of its periplasmic region that compares favorably to the crystal structure. These results provide the foundation to study conformation changes from interaction with partner proteins.
