共查询到20条相似文献，搜索用时 31 毫秒
1.
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
2.
Ganti S. Murthy Devon E. Townsend Gavin L. Meerdink Gerald L. Bargren Mike E. Tumbleson Vijay Singh 《Cereal Chemistry》2005,82(3):302-304
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
3.
Fractionating the corn kernel to separate endosperm from germ and pericarp improves corn ethanol processing by increasing fermentation throughput and generating salable coproducts. One fractionation technology, dry fractionation (DF), suffers from loss of germ‐derived nutrients and amino acids, resulting in poor fermentation performance. Such deficiencies may be addressed by increasing nitrogen and other nutritional supplementation. As an alternative to exogenous nitrogen source, we investigated the use of a fungal protease to generate free amino nitrogen (FAN) from corn endosperm. Incubation of endosperm with protease did not affect subsequent liquefaction and saccharification. FAN supplementation through proteolysis resulted in fermentation being 99% complete in 48 hr, compared to 93% maximum with urea supplementation. Viable cell growth rates were similar in FAN and urea‐supplemented fermentations. Urea and FAN addition resulted in similar fermentation characteristics and similar FAN consumption rates as with FAN alone, which was indicative that FAN was assimilated preferentially. Increased amounts of maltose remaining after fermentation were correlated with initial FAN concentrations in mash. This observed trend was implicated in ethanol yield reduction of 2 g/L at high protease loading (generating 1.6 mg of FAN/g of glucose substrate) compared to a urea control. Using a glucose and maltose solution, we confirmed higher residual maltose in fermentations supplemented with high FAN concentrations. Use of protease to generate optimal FAN concentration in mash (1.2 mg of FAN/g of glucose substrate) could improve economics of dry fractionated corn ethanol production by increasing fermentation rates and, consequently, reducing fermentation time. 相似文献
4.
Optimization of simultaneous saccharification and fermentation for the production of ethanol from lignocellulosic biomass 总被引：4，自引：0，他引：4
Simultaneous saccharification and fermentation (SSF) of alkaline hydrogen peroxide pretreated Antigonum leptopus (Linn) leaves to ethanol was optimized using cellulase from Trichoderma reesei QM-9414 (Celluclast from Novo) and Saccharomyces cerevisiae NRRL-Y-132 cells. Response surface methodology (RSM) and a three-level four-variable design were employed to evaluate the effects of SSF process variables such as cellulase concentration (20-100 FPU/g of substrate), substrate concentration (5-15% w/v), incubation time (24-72 h), and temperature (35-45 degrees C) on ethanol production efficiency. Cellulase and substrate concentrations were found to be the most significant variables. The optimum conditions arrived at are as follows: cellulase = 100 FPU/g of substrate, substrate = 15% (w/v), incubation time = 57.2 h, and temperature = 38.5 degrees C. At these conditions, the predicted ethanol yield was 3.02% (w/v) and the actual experimental value was 3.0% (w/v). 相似文献
5.
Divya Ramchandran Ping Wang Bruce Dien Wei Liu Michael A. Cotta Vijay Singh 《Cereal Chemistry》2015,92(2):218-223
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
6.
Ping Wang Vijay Singh Hua Xue David B. Johnston Kent D. Rausch M. E. Tumbleson 《Cereal Chemistry》2007,84(1):10-14
In a conventional dry‐grind corn process, starch is converted into dextrins using liquefaction enzymes at high temperatures (90–120°C) during a liquefaction step. Dextrins are hydrolyzed into sugars using saccharification enzymes during a simultaneous saccharification and fermentation (SSF) step. Recently, a raw starch hydrolyzing enzyme (RSH), Stargen 001, was developed that converts starch into dextrins at low temperatures (<48°C) and hydrolyzes dextrins into sugars during SSF. In this study, a dry‐grind corn process using RSH enzyme was compared with two combinations (DG1 and DG2) of commercial liquefaction and saccharification enzymes. Dry‐grind corn processes for all enzyme treatments were performed at the same process conditions except for the liquefaction step. For RSH and DG1 and DG2 treatments, ethanol concentrations at 72 hr of fermentation were 14.1–14.2% (v/v). All three enzyme treatments resulted in comparable ethanol conversion efficiencies, ethanol yields, and DDGS yields. Sugar profiles for the RSH treatment were different from DG1 and DG2 treatments, especially for glucose. During SSF, the highest glucose concentration for RSH treatment was 7% (w/v), whereas for DG1 and DG2 treatments, glucose concentrations had maximum of 19% (w/v). Glycerol concentrations were 0.5% (w/v) for RSH treatment and 0.8% (w/v) for DG1 and DG2 treatments. 相似文献
7.
以菊芋粉为原料同步糖化发酵生产燃料乙醇 总被引：3，自引：1，他引：3
利用粟酒裂殖酵母（Schizosaccharomyces pombe）能发酵菊芋未水解糖液高产乙醇的特点提出了以菊芋粉为原料,同步糖化发酵生产燃料乙醇的新工艺。在摇瓶中考察了原料预处理方法、原料浓度和初始pH值对乙醇发酵的影响,进而在5 L发酵罐中考察了未调控pH值和恒定pH值与通气情况对乙醇发酵的影响。结果表明：该菌株最适pH值为4.0;100目筛分的菊芋粉发酵效果良好,115℃灭菌处理优于121℃,在此条件下,菊芋粉浓度200 g/L时,乙醇产量达到66.58 g/L,理论转化率为85.88%;发酵液pH值下降对乙醇发酵没有影响,通入适量氧气会导致乙醇产量的下降,这表明粟酒裂殖酵母进行乙醇发酵时不需要供氧;通入氮气保持厌氧环境不能显著提高乙醇产量,不通气进行乙醇发酵也达到高的转化率,因此在工业生产中,不必保持厌氧发酵环境。在此基础上,对菊芋粉补料发酵进行了试验,补料至菊芋粉终浓度为300 g/L,发酵终点乙醇浓度为94.81 g/L,理论转化率为81.54%。这些研究工作,为以菊芋为原料的燃料乙醇工业化生产提供技术依据。 相似文献
8.
Four pearl millet genotypes were tested for their potential as raw material for fuel ethanol production in this study. Ethanol fermentation was performed both in flasks on a rotary shaker and in a 5‐L bioreactor using Saccharomyces cerevisiae (ATCC 24860). For rotary‐shaker fermentation, the final ethanol yields were 8.7–16.8% (v/v) at dry mass concentrations of 20–35%, and the ethanol fermentation efficiencies were 90.0–95.6%. Ethanol fermentation efficiency at 30% dry mass on a 5‐L bioreactor reached 94.2%, which was greater than that from fermentation in the rotary shaker (92.9%). Results showed that the fermentation efficiencies of pearl millets, on a starch basis, were comparable to those of corn and grain sorghum. Because pearl millets have greater protein and lipid contents, distillers dried grains with solubles (DDGS) from pearl millets also had greater protein content and energy levels than did DDGS from corn and grain sorghum. Therefore, pearl millets could be a potential feedstock for fuel ethanol production in areas too dry to grow corn and grain sorghum. 相似文献
9.
Bernardo C. Vidal David B. Johnston Kent D. Rausch M. E. Tumbleson Vijay Singh 《Cereal Chemistry》2011,88(3):328-332
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
10.
Ganti S. Murthy Vijay Singh David B. Johnston Kent D. Rausch M. E. Tumbleson 《Cereal Chemistry》2006,83(5):455-459
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
11.
A modified dry‐grind process that combined the use of conventional amylases (glucoamylase [GA]), phytase, and granular starch hydrolyzing enzymes (GSHE) to achieve low liquefaction viscosities and low glucose concentrations during simultaneous saccharification and fermentation (SSF) with a high slurry solids content (>33% w/w) was developed. Doses of GSHE and GA were optimized for the modified process. At 35% solids content, the modified process had 80% lower slurry viscosity, 24% lower peak glucose concentration, 7.5% higher final ethanol concentration, and 51% higher fermentation rate compared with the conventional dry‐grind process. At 40% solids content, the modified process had lower viscosities, lower peak and residual glucose concentrations, and higher ethanol concentrations than the conventional process; however, the results were in contrast to those for 35% solids content. At 40% solids content, SSF did not run to completion for conventional or modified processes, and more than 2.5% w/v of residual glucose was left in the fermentation broth. Final ethanol concentration achieved with the modified process at 40% solids content was 19.5% v/v, similar to the ethanol concentration achieved with the modified process at 35% solids content. At 35% slurry solids content, a GSHE level of 1.25 μL/g db of corn and a GA level of 0.25 μL/g db of corn were selected as optimum enzyme doses for the modified process. 相似文献
12.
Esther Prez‐Carrillo Sergio O. Serna‐Saldívar Mario M. Alvarez M. Luisa Cortes‐Callejas 《Cereal Chemistry》2008,85(6):792-798
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
13.
温度对固定化酵母酒精分批发酵的影响及动力学模型 总被引：1，自引：0，他引：1
该文以甜高粱茎秆汁液为原料,探讨了温度（25～37 ℃）对甜高粱汁固定化酵母酒精分批发酵的影响,并对不同温度下固定化酵母乙醇发酵的动力学模型进行了研究。结果表明：温度的升高可以提高细胞生长速率,但过高的温度却阻碍了细胞的生长,从而影响了酒精的产量。应用Hinshelwood模型,分别对酒精发酵过程中细胞生长动力学和酒精合成动力学进行了模拟,得到25～34℃范围内不同温度下各种动力学参数。在此基础上,进一步研究了温度同细胞生长动力学参数之间的内在联系,得到酒精分批发酵过程中酵母细胞质量浓度的变化同温度以及底物质量浓度之间的一般关系式,验证试验结果表明,该模型具有很好的适用性。 相似文献
14.
Shuping Yan Xiaorong Wu Scott R. Bean Jeffery F. Pedersen Tesfaye Tesso Yuanhong R. Chen Donghai Wang 《Cereal Chemistry》2011,88(6):589-595
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
15.
Logistic模型模拟乙醇发酵产物动力学 总被引：1，自引：0，他引：1
乙醇发酵产物动力学的研究有助于更好的认识发酵过程,为其工业放大及生产操作条件的优化提供理论基础。基于Logistic方程的菌体生长动力学模型可较好的描述细胞生长期及细胞自身抑制作用,但由于该模型方程中的比例参数与积分常数没有明显的生物学意义,使其应用受到了限制。该文从生物学与化学工程学结合角度对Logistic模型方程重新参数化,将发酵产物乙醇生成动力学与酵母生长动力学方程类比,给出了乙醇浓度的显式函数模型,模型中不再出现酵母菌浓度变量,大大简化了模型,并且赋予参数其物理意义;在研究了以葡萄糖和玉米淀粉为原料乙醇质量浓度、总糖质量浓度在不同底物质量浓度和料液比条件下随发酵时间的变化规律的基础上运用该模型拟合了以葡萄糖和玉米淀粉为原料进行乙醇发酵的试验数据,结果表明:模型值与试验数据具有较好一致性,拟合度均大于0.97,可见该重新参数化的Logistic模型可以描述发酵生产乙醇过程中产物乙醇的动力学行为,具有预测工业上实际发酵过程中乙醇浓度的潜力。 相似文献
16.
甜高粱茎汁及茎渣同步糖化发酵工艺优化 总被引：1，自引：2，他引：1
为了提高甜高粱秸秆乙醇生产中茎汁和茎渣的利用,以甜高粱茎汁及其渣为发酵原料,对茎汁茎渣混合原料同步糖化乙醇发酵的工艺条件进行优化研究。采用Plackett-Burman(PB)筛选设计试验筛选出影响甜高粱茎秆渣汁同步糖化乙醇发酵的显著因素。采用响应面法建立了同步糖化发酵乙醇生产的乙醇产量数学模型。根据该模型进行了工艺参数的优化,以乙醇产量为指标,试验所得甜高粱茎秆渣汁同步糖化化乙醇发酵的优化工艺条件为:发酵温度36.58℃,混合纤维素酶添加量=23.5(FBU/m L)/35.25(CBU/m L),甜高粱渣汁质量体积比为8.2%,理论预测乙醇产量为89.2%,在此条件下进行验证试验,乙醇产量为88.98%,平均质量浓度,验证了数学模型的有效性,为提高甜高粱茎汁及茎渣混合原料同步糖化发酵产乙醇和提高发酵效率提供参考。 相似文献
17.
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
18.
Field peas (Pisum sativum) were evaluated as a potential feedstock for ethanol production. Ground peas were dry‐milled and separated into starch, protein, and fibrous fractions by air classification. Starch‐enriched fractions prepared from whole peas and dehulled peas contained 73.7% wt and 77.8% wt starch, respectively, a nearly two‐fold enrichment compared with whole peas. The fractions were liquefied and saccharified using industrial α‐amylase and glucoamylase at recommended enzyme loadings. A final ethanol concentration of 11.0% (w/v) was obtained in 48–52 hr, with yields of 0.43–0.48 g of ethanol/g of glucose. Starch present in whole ground peas was also saccharified and fermented, with 97% of the starch fermented when an autoclaving step was included in the liquefaction stage. 相似文献
19.
合成气/CO发酵制备燃料乙醇是一项具有吸引力的新技术,为促进C.autoethanogenum在该技术中的应用,对C.autoethanogenum的乙醇发酵工艺及过程参数进行了研究。结果表明,C.autoethanogenum代谢木糖的产物以乙酸为主,只产生少量乙醇;与无机氮源相比较,C.autoethanogenum在含有机氮源的培养基中生长迅速,菌体浓度高。在3 L发酵罐中进行C.autoethanogenum的批式发酵试验,采用木糖生长-CO发酵两步法,乙醇主要在CO发酵阶段产生,最高乙醇质量浓度为1.71 g/L;发酵罐经改进之后,采用CO一步法发酵,虽然得到的菌体浓度降低了,但是发酵时间延长,最高乙醇质量浓度达到7.36 g/L,而乙酸质量浓度在整个发酵过程中均低于1.1 g/L。此外,研究发现发酵液的pH值和氧化还原电位ORP与乙酸/乙醇产物分布密切相关,尤其是pH值。上述研究结果可为C.autoethanogenum发酵CO生产乙醇的中试放大提供参考。 相似文献
20.
X. Wu R. Zhao S. R. Bean P. A. Seib J. S. McLaren R. L. Madl M. Tuinstra M. C. Lenz D. Wang 《Cereal Chemistry》2007,84(2):130-136
The goal of this research is to understand the key factors affecting ethanol production from grain sorghum. Seventy genotypes and elite hybrids with a range of chemical compositions and physical properties selected from ≈1,200 sorghum lines were evaluated for ethanol production and were used to study the relationships of composition, grain structure, and physical features that affect ethanol yield and fermentation efficiency. Variations of 22% in ethanol yield and 9% in fermentation efficiency were observed among the 70 sorghum samples. Genotypes with high and low conversion efficiencies were associated with attributes that may be manipulated to improve fermentation efficiency. Major characteristics of the elite sorghum genotypes for ethanol production by the dry-grind method include high starch content, rapid liquefaction, low viscosity during liquefaction, high fermentation speed, and high fermentation efficiency. Major factors adversely affecting the bioconversion process are tannin content, low protein digestibility, high mash viscosity, and an elevated concentration of amylose-lipid complex in the mash. 相似文献