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1.
Corn endosperm separated by dry fractionation could exhibit poor fermentation performance due to loss of germ components beneficial for yeast growth. Inorganic nitrogen and other nutritional supplementations are used to overcome slow fermentation rates. We investigated the use of a protease in generating free amino nitrogen (FAN) from germ as an alternative to exogenous nitrogen sources. Up to 300% more FAN can be generated from germ in 6 hr of incubation with protease than without protease. Protease incubation also resulted in higher dry solids (ds) and total glucose contents in the germ hydrolyzates. During fermentation without urea addition, ethanol yields were dependent on mash FAN concentrations. Ethanol yields increased to a maximum when FAN level was 80–90 mg of FAN/100 g ds. At half the optimal FAN level (≈40 mg of FAN/100 g ds), nitrogen limitation occurred, as indicated by high residual glucose concentrations. However, germ FAN did not increase the ethanol yields compared to urea supplementation, likely because germ FAN resulted in lower substrate consumption compared to urea supplementation. Lower substrate consumption correlated to the increase in residual maltose with increase in initial FAN. Ethanol productivity in 0–24 hr of fermentation was higher with germ FAN than with urea, thus decreasing overall fermentation time.  相似文献   

2.
To improve fractionation efficiency in modified dry grind corn processes, we evaluated the effectiveness of protease treatment in reducing residual starch in endosperm fiber. Three schemes of protease treatment were conducted in three processes: 1) enzymatic milling or E‐Mill, 2) dry fractionation with raw starch fermentation or dry RS, and 3) dry fractionation with conventional fermentation or dry conv. Kinetics of free amino nitrogen production were similar in both dry and wet fractionation (E‐Mill), indicating that proteolysis was effective in all three schemes. At the end of fermentation, endosperm fiber was recovered and its residual starch measured. Using protease treatment, residual starch in the endosperm fiber was reduced by 1.9% w/w (22% relative reduction) in dry conv and 1.7% w/w (8% relative reduction) in dry RS, while no reduction was observed in the E‐Mill process. Protease treatment increased ethanol production rates early in fermentation (≤24 hr) but final ethanol concentrations were unaffected in both dry RS and E‐Mill. In dry conv, the addition of protease resulted in a decline in final ethanol concentration by 0.3% v/v, as well as a higher variability in liquefaction product concentration (higher standard deviations in the glucose and maltose yields). Protease treatment can be used effectively to enhance modified dry grind processes.  相似文献   

3.
New corn fractionation technologies that produce higher value coproducts from dry‐grind processing have been developed. Wet fractionation technologies involve a short soaking of corn followed by milling to recover germ and pericarp fiber in an aqueous medium before fermentation of degermed defibered slurry. In dry fractionation technologies, a dry degerm defiber (3D) process (similar to conventional corn dry‐milling) is used to separate germ and pericarp fiber before fermentation of the endosperm fraction. The effect of dry and wet fractionation technologies on the fermentation rates and ethanol yields were studied and compared with the conventional dry‐grind process. The wet process had the highest fermentation rate. The endosperm fraction obtained from 3D process had lowest fermentation rate and highest residual sugars at the end of fermentation. Strategies to improve the fermentation characteristics of endosperm fraction from 3D process were evaluated using two saccharification and fermentation processes. The endosperm fraction obtained from 3D process was liquefied by enzymatic hydrolysis and fermented using either separate saccharification (SS) and fermentation or simultaneous saccharification and fermentation (SSF). Corn germ soak water and B‐vitamins were added during fermentation to study the effect of micronutrient addition. Ethanol and sugar profiles were measured using HPLC. The endosperm fraction fermented using SSF produced higher ethanol yields than SS. Addition of B‐vitamins and germ soak water during SSF improved fermentation of 3D process and resulted in 2.6 and 2.3% (v/v) higher ethanol concentrations and fermentation rates compared with 3D process treatment with no addition of micronutrients.  相似文献   

4.
Different corn types were used to compare ethanol production from the conventional dry‐grind process to wet or dry fractionation processes. High oil, dent corn with high starch extractability, dent corn with low starch extractability and waxy corn were selected. In the conventional process, corn was ground using a hammer mill; water was added to produce slurry which was fermented. In the wet fractionation process, corn was soaked in water; germ and pericarp fiber were removed before fermentation. In the dry fractionation process, corn was tempered, degerminated, and passed through a roller mill. Germ and pericarp fiber were separated from the endosperm. Due to removal of germ and pericarp fiber in the fractionation methods, more corn was used in the wet (10%) and dry (15%) fractionation processes than in the conventional process. Water was added to endosperm and the resulting slurry was fermented. Oil, protein, and residual starch in germ were analyzed. Pericarp fiber was analyzed for residual starch and neutral detergent fiber (NDF) content. Analysis of variance and Fisher's least significant difference test were used to compare means of final ethanol concentrations as well as germ and pericarp fiber yields. The wet fractionation process had the highest final ethanol concentrations (15.7% v/v) compared with dry fractionation (15.0% v/v) and conventional process (14.1% v/v). Higher ethanol concentrations were observed in fractionation processes compared to the conventional process due to higher fermentable substrate per batch available as a result of germ and pericarp fiber removal. Germ and pericarp yields were 7.47 and 6.03% for the wet fractionation process and 7.19 and 6.22% for the dry fractionation process, respectively. Germ obtained from the wet fractionation process had higher oil content (34% db) compared with the dry fractionation method (11% db). Residual starch content in the germ fraction was 16% for wet fractionation and 44% for dry fractionation. Residual starch in the pericarp fiber fraction was lower for the wet fractionation process (19.9%) compared with dry fractionation (23.7%).  相似文献   

5.
Preliminary calculations showed that recovery of fiber before fermentation in the dry grind ethanol facilities known as the Quick Fiber process increases fermenter capacity and reduces ethanol production cost by as much as 4 ¢/gal. The objective of the current research was to evaluate the effect of mash temperature, dry solids, and residual germ on fiber yield and purity when using the quick fiber process. Fiber was recovered by flotation and skimming, while maintaining a specified temperature, dry solids, and residual germ in the mash. Varying temperature and dry solids in the mash resulted in a statistically significant effect on the fiber yield, neutral detergent fiber (NDF) content, and weight of NDF/100 g of dry corn. Varying residual germ in the mash resulted in statistically significant differences for NDF through dilution and the weight of NDF/100 g of dry corn. The highest fiber yield was 10.9% at 45°C, 23% dry solids, and 15% residual germ; the highest NDF was 50.9% at 30°C, 21% dry solids, and 0% residual germ. The highest weight of NDF/100 g of dry corn was observed at 45°C, 23% dry solids, and 0% residual germ.  相似文献   

6.
Ethanol fermentation of dry‐fractionated grits (corn endosperm pieces) containing different levels of germ was studied with the dry‐grind process. Partial removal of the germ fraction allows for marketing the germ fraction and potentially more efficient fermentation. Grits obtained from a dry‐milling plant were mixed with different amounts of germ (2, 5, 7, and 10% germ of the total sample) and compared with control grits (0% germ). Fermentation rates of germ‐supplemented grits (2, 5, 7, and 10% germ) were faster than control grits (0% germ). Addition of 2% germ was sufficient to achieve a high ethanol concentration (19.06% v/v) compared with control grits (18.18% v/v). Fermentation of dry‐fractionated grits (92, 95, and 97% grits) obtained from a commercial facility was also compared with ground whole corn (control). Fermentation rates were slower and final ethanol concentrations were lower for commercial grits than the control sample. However, in a final experiment, commercial grits were subjected to raw starch hydrolyzing (RSH) enzyme, resulting in higher ethanol concentrations (20.22, 19.90, and 19.49% v/v for 92, 95, and 97% grits, respectively) compared with the whole corn control (18.64% v/v). Therefore, high ethanol concentrations can be achieved with dry‐fractionated grits provided the inclusion of a certain amount of germ and the use of RSH enzyme for controlled starch hydrolysis.  相似文献   

7.
A detailed economic analysis of a 914 tonnes/day (36,000 bu/day) “Quick Germ” ethanol process was performed. The Quick Germ ethanol process is a combination of a dry-grind and a wet-milling ethanol process. The Quick Germ ethanol process increases the coproduct value in the dry-grind ethanol process by recovering germ before fermentation. Germ is recovered using the conventional wet-milling degermination process. Economic assessment of the Quick Germ process proved profitable. The savings achieved by recovering germ as a coproduct and by increasing the fermentor capacity due to removal of nonfermentables from the corn mash will reduce the manufacturing cost of ethanol by 2.69 ¢/L (10.19 ¢/gal or $0.265/bu) when compared to the conventional dry-grind ethanol process.  相似文献   

8.
Normal gravity rye and triticale mashes, containing 20–21 g of dissolved solids per 100 mL of mash liquid, were fermented with active dry yeast at 27°C. Fermentations were completed within 48 hr for rye, and within 72 hr for triticale. Supplementation of mashes with urea at a concentration of 8 mM accelerated rates of sugar consumption and fermentation, and reduced fermentation time from 48 to 36 hr for rye, and from 72 to 48 hr for triticale. Rye fermented faster than triticale, due to its higher level of free amino nitrogen. Ethanol yields were 356–363 L/tonne of 14% moisture rye grain, and 362–367 L/tonne of 14% moisture triticale. Fermentation efficiencies, which were 90–91% for triticale, and 91–93% for rye, and ethanol yields were comparable to those obtained from wheat and were not affected significantly by urea supplementation. The replacement of wheats by less expensive crops such as rye and triticale would provide good economic opportunities and alternatives for the fuel alcohol industry.  相似文献   

9.
The aim was to study the dual effect of sorghum decortication and protease treatment before liquefaction with α‐amylase on the performance of subsequent steps of saccharification and fermentation. A bifactorial experiment with a level of confidence of P < 0.05 was designed to study differences among grains (maize, whole, and decorticated sorghum) and the effectiveness of the protease before liquefaction. Sorghum was decorticated to remove most of the pericarp and part of the germ and increase starch concentration of the feedstock. The decorticated sorghum had significantly higher starch hydrolysis during liquefaction compared with the whole kernel. These hydrolyzates contained ≈50% more reducing sugars than the untreated counterparts. At the end of saccharification, the final glucose concentration in hydrolyzates treated without protease was the highest for maize (180 mg/mL), followed by decorticated sorghum (165 mg/mL), and whole sorghum (145 mg/mL). Decortication and protease treatment had a significant effect on fermentation times. In decorticated sorghum mash treated with and without protease, fermentation times were 22 and 60 hr, respectively. The decorticated sorghum treated with protease yielded similar amounts of ethanol compared with maize and 44% more ethanol compared with the untreated whole sorghum. Both sorghum decortication and protease treatments before hydrolysis with α‐amylase are recommended to increase ethanol yields, lower yields of distilled grains, and save liquefaction, saccharification, and fermentation times.  相似文献   

10.
A modified dry‐grind corn process has been developed that allows recovery of both pericarp and endosperm fibers as coproducts at the front end of the process before fermentation. The modified process is called enzymatic milling (E‐Mill) dry‐grind process. In a conventional dry‐grind corn process, only the starch component of the corn kernel is converted into ethanol. Additional ethanol can be produced from corn if the fiber component can also be converted into ethanol. In this study, pericarp and endosperm fibers recovered in the E‐Mill dry‐grind process were evaluated as a potential ethanol feedstock. Both fractions were tested for fermentability and potential ethanol yield. Total ethanol yield recovered from corn by fermenting starch, pericarp, and endosperm fibers was also determined. Results show that endosperm fiber produced 20.5% more ethanol than pericarp fiber on a g/100 g of fiber basis. Total ethanol yield obtained by fermenting starch and both fiber fractions was 0.370 L/kg compared with ethanol yield of 0.334 L/kg obtained by fermenting starch alone.  相似文献   

11.
A high‐tannin sorghum cultivar with 3.96% tannin content was used to study the effects of germination on its ethanol fermentation performance in a laboratory dry‐grind process. High‐tannin sorghum sample was germinated for 3 and 4 days. Original and germinated samples were analyzed for tannin, starch, protein, free amino nitrogen (FAN), and glucose content. Endosperm structures and flour pasting properties of germinated and nongerminated sorghum samples were examined using a scanning electron microscope (SEM) and rapid visco analyzer (RVA). Germination reduced tannin content from 3.96% to negligible levels. The free fermentable sugars (glucose, maltose, and maltotriose) in the germinated samples were significantly higher than those in the nongerminated control. Judged by the starch (starch plus dextrin) and free amino nitrogen contents in the mashed samples, germination improved degree of hydrolysis for starch by 13–20% and for protein by 5‐ to 10‐fold during mashing. Germination significantly shortened the required fermentation time for ethanol production by 24–36 hr, increased ethanol fermentation efficiency by 2.6–4.0%, and reduced the residual starch content in the distillers dried grain with solubles (DDGS) compared to the nongerminated control. Ethanol yield for the 3‐day germinated samples was 2.75 gallons/bushel, which was 3.1% higher than the 2.67 gallons for the nongerminated control. Ethanol yield for the 4‐day germinated sorghum was 2.63 gallons/bushel due to excessive loss of starch during germination.  相似文献   

12.
We studied the effect of sorghum decortication and protease treatment on starch hydrolysis before liquefaction with thermoresistant α-amylase and the generation of free amino nitrogen (FAN) in preparation for subsequent steps of ethanol production. A bifactorial experiment with a level of confidence of P < 0.05 was designed to study differences among maize, whole sorghum, and decorticated sorghum and the effectiveness of the protease treatment before starch liquefaction. Sorghum was decorticated 9.7% to remove most of the pericarp and part of the germ and increase starch concentration. Starch concentration increased in decorticated kernels, whereas total phenols, fiber, and fat decreased. The decorticated sorghum had significantly higher starch and protein hydrolysis compared with the whole kernel. Protease treatment before liquefaction improved the rate of starch hydrolysis, especially in mashes from whole and decorticated sorghums. Whole and decorticated sorghum hydrolyzates treated with protease contained ≈50% more reducing sugars than the untreated counterparts. Maize yielded hydrolyzates with the the highest amount of FAN, followed by decorticated and whole sorghums. The maize and both sorghum hydrolyzates treated with protease contained ≈60 and 30% more FAN compared with the untreated counterparts. Both sorghum decortication and protease treatments before hydrolysis with α-amylase are recommended to increase ethanol yields, save processing time (and therefore energy), and to produce mashes with higher FAN content, which is considered as an important yeast substrate.  相似文献   

13.
A new low temperature liquefaction and saccharification enzyme STARGEN 001 (Genencor International, Palo Alto, CA) with high granular starch hydrolyzing activity was used in enzymatic dry‐grind corn process to improve recovery of germ and pericarp fiber before fermentation. Enzymatic dry‐grind corn process was compared with conventional dry‐grind corn process using STARGEN 001 with same process parameters of dry solid content, pH, temperature, enzyme and yeast usage, and time. Sugar, ethanol, glycerol and organic acid profiles, fermentation rate, ethanol and coproducts yields were investigated. Final ethanol concentration of enzymatic dry‐grind corn process was 15.5 ± 0.2% (v/v), which was 9.2% higher than conventional process. Fermentation rate was also higher for enzymatic dry‐grind corn process. Ethanol yields of enzymatic and conventional dry‐grind corn processes were 0.395 ± 0.006 and 0.417 ± 0.002 L/kg (2.65 ± 0.04 and 2.80 ± 0.01 gal/bu), respectively. Three additional coproducts, germ 8.0 ± 0.4% (db), pericarp fiber 7.7 ± 0.4% (db), and endosperm fiber 5.2 ± 0.6% (db) were produced in addition to DDGS with enzymatic dry‐grind corn process. DDGS generated from enzymatic dry‐grind corn process was 66% less than conventional process.  相似文献   

14.
Fermentation performance of eight waxy, seven nonwaxy soft, and 15 nonwaxy hard wheat cultivars was compared in a laboratory dry‐grind procedure. With nitrogen supplements in the mash, the range of ethanol yields was 368–447 L/ton. Nonwaxy soft wheat had an average ethanol yield of 433 L/ton, higher than nonwaxy hard and waxy wheat. Conversion efficiencies were 91.3–96.2%. Despite having higher levels of free sugars in grain, waxy wheat had higher conversion efficiency than nonwaxy wheat. Although there was huge variation in the protein content between nonwaxy hard and soft wheat, no difference in conversion efficiency was observed. Waxy cultivars had extremely low peak viscosity during liquefaction. Novel mashing properties of waxy cultivars were related to unique pasting properties of starch granules. With nitrogen supplementation, waxy wheat had a faster fermentation rate than nonwaxy wheat. Fermentation rates for waxy cultivars without nitrogen supplementation and nonwaxy cultivars with nitrogen supplementation were comparable. Ethanol yield was highly related to both total starch and protein content, but total starch was a better predictor of ethanol yield. There were strong negative relationships between total starch content of grain and both yield and protein content of distillers dried grains with solubles (DDGS).  相似文献   

15.
The efficiency of fractionating cereal grains (e.g., dry corn milling) can be evaluated and monitored by quantifying the proportions of seed tissues in each of the recovered fractions. The quantities of individual tissues are typically estimated using indirect methods such as quantifying fiber or ash to indicate pericarp and tip cap contents, and oil to indicate germ content. More direct and reliable methods are possible with tissue‐specific markers. We used two transgenic maize lines, one containing the fluorescent protein green fluorescent protein (GFP) variant S65T expressed in endosperm, and the other containing GFP expressed in germ to determine the fate of each tissue in the dry‐milling fractionation process. The two lines were dry‐milled to produce three fractions (bran‐, endosperm‐, and germ‐rich fractions) and GFP fluorescence was quantified in each fraction to estimate the tissue composition. Using a simplified laboratory dry‐milling procedure and our GFP‐containing grain, we determined that the endosperm‐rich fraction contained 4% germ tissue, the germ‐rich fraction contained 28% germ, 20% endosperm, and 52% nonendosperm and nonembryo tissues, and the bran‐rich fraction contained 44% endosperm, 13% germ, and 43% nonendosperm and nonembryo tissues. GFP‐containing grain can be used to optimize existing fractionation methods and to develop improved processing strategies.  相似文献   

16.
Nitrogen deficiencies in grape musts are one of the main causes of stuck or sluggish wine fermentations. In the present study, we have supplemented nitrogen-deficient fermentations with a mixture of ammonium and amino acids at various stages throughout the alcoholic fermentation. The timing of the nitrogen additions influenced the biomass yield, the fermentation performance, the patterns of ammonium and amino acid consumption, and the production of secondary metabolites. These nitrogen additions induced a nitrogen-repressed situation in the cells, and this situation determined which nitrogen sources were selected. Glutamine and tryptophan were the main amino acids consumed in all the fermentations. Ammonium is the preferred nitrogen source for biomass production but was hardly consumed when it was added in the final stages of the fermentation. The higher ammonium consumption in some fermentations correlated with a greater synthesis of glycerol, acetate, and acetaldehyde but with a lower synthesis of higher alcohols.  相似文献   

17.
The objective of this research was to investigate the fermentation performance of waxy grain sorghum for ethanol production. Twenty‐five waxy grain sorghum varieties were evaluated with a laboratory dry‐grind procedure. Total starch and amylose contents were measured following colorimetric procedures. Total starch and amylose contents ranged from 65.4 to 76.3% and from 5.5 to 7.3%, respectively. Fermentation efficiencies were in the range of 86.0–92.2%, corresponding to ethanol yields of 2.61–3.03 gallons/bushel. The advantages of using waxy sorghums for ethanol production include easier gelatinization and low viscosity during liquefaction, higher starch and protein digestibility, higher free amino nitrogen (FAN) content, and shorter fermentation times. The results showed a strong linear relationship between FAN content and fermentation rate. Fermentation rate increased as FAN content increased, especially during the first 30 hr of fermentation (R2 = 0.90). Total starch content in distillers dried grains with solubles (DDGS) was less than 1% for all waxy varieties.  相似文献   

18.
为了优化玉米固态发酵生产红曲红色素的主要补加营养物,采用析因试验设计确定了紫红曲霉M144固态发酵红曲红色素的主要影响因子为葡萄糖、硫酸镁和酵母膏添加量,采用Box-Behnken试验设计和响应面优化分析确定了补加营养物的最佳添加量分别为葡萄糖0.26%(w/w),硫酸镁0.43%(w/w),酵母膏0.25%(w/w),在此条件下红曲红色素红色价为2335.17U/g,色调为1.69,比未补加营养物时分别提高了55.67%和64.08%。通过对玉米固态发酵过程中补加营养物质的系统研究,提高了红曲红色素的产量和质量,可为玉米固态发酵红曲红色素的生产提供技术支持。  相似文献   

19.
Aflatoxins, like all mycotoxins, are toxic fungal metabolites that can have adverse health effects on animals and human beings. Aflatoxins are a major concern for the dry‐grind corn processing industry as it is believed that aflatoxins affect yeast and reduce its efficacy in producing ethanol. In the present study, aflatoxin B1 (100, 200, 350, or 775 ppb) was added to mycotoxin‐free corn and laboratory‐scale fermentations were conducted. No effect of aflatoxin B1 was observed on the fermentation rates or final ethanol concentrations. Mean ethanol concentration in the fermenter was 14.01–14.51% (v/v) at 60 hr for all the treatments. In the dry‐grind ethanol process, 55% of aflatoxin B1 was detected in wet grains and 45% in thin stillage.  相似文献   

20.
蒸汽爆破预处理和微生物发酵对玉米秸秆降解率的影响   总被引：7，自引：2，他引：5  
为了提高玉米秸秆的利用效率,首先对玉米秸秆进行蒸汽爆破预处理（压力2.5 Mpa,维压200 s）,然后再进行米曲霉发酵,研究物理和生物学处理对秸秆成分及相关酶活变化的影响。结果表明,蒸汽爆破使秸秆中纤维素、半纤维素和木质素的降解率分别达到8.47%、50.45% 和36.65% （p＜0.05）。爆破预处理的秸秆再经米曲霉发酵6 d后,秸秆中纤维素和半纤维素的降解率分别为27.89%和64.80% （p＜0.05）,发酵秸秆中的滤纸酶、羧甲基纤维素酶、淀粉酶和蛋白酶活力分别达到335.10、1138.92、1954.20和201.99 U/g。爆破预处理后进行米曲霉发酵,对于提高玉米秸秆的降解率具有非常重要的意义。  相似文献   

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