Enzyme production by wood-rot and soft-rot fungi cultivated on corn fiber followed by simultaneous saccharification and fermentation

This research aims at developing a biorefinery platform to convert lignocellulosic corn fiber into fermentable sugars at a moderate temperature (37 °C) with minimal use of chemicals. White-rot (Phanerochaete chrysosporium), brown-rot (Gloeophyllum trabeum), and soft-rot (Trichoderma reesei) fungi were used for in situ enzyme production to hydrolyze cellulosic and hemicellulosic components of corn fiber into fermentable sugars. Solid-substrate fermentation of corn fiber by either white- or brown-rot fungi followed by simultaneous saccharification and fermentation (SSF) with coculture of Saccharomyces cerevisiae has shown a possibility of enhancing wood rot saccharification of corn fiber for ethanol fermentation. The laboratory-scale fungal saccharification and fermentation process incorporated in situ cellulolytic enzyme induction, which enhanced overall enzymatic hydrolysis of hemi/cellulose components of corn fiber into simple sugars (mono-, di-, and trisaccharides). The yeast fermentation of the hydrolyzate yielded 7.8, 8.6, and 4.9 g ethanol per 100 g corn fiber when saccharified with the white-, brown-, and soft-rot fungi, respectively. The highest ethanol yield (8.6 g ethanol per 100 g initial corn fiber) is equivalent to 35% of the theoretical ethanol yield from starch and cellulose in corn fiber. This research has significant commercial potential to increase net ethanol production per bushel of corn through the utilization of corn fiber. There is also a great research opportunity to evaluate the remaining biomass residue (enriched with fungal protein) as animal feed.     

Optimization of simultaneous saccharification and fermentation for the production of ethanol from lignocellulosic biomass

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).     

Production of L-lactic acid and oligomeric compounds from apple pomace by simultaneous saccharification and fermentation: a response surface methodology assessment

The potential of apple pomace for lactic acid production by simultaneous saccharification and fermentation (SSF) was evaluated. The effects of the cellulase to solid ratio (CSR), the liquor to solid ratio (LSR), and the beta-glucosidase to cellulase ratio (BCR) on the kinetics of lactic acid generation were assessed, and a set of mathematical models was developed to reproduce and predict the lactic acid concentration of fermentation broths. Operating at low cellulase and cellobiase charges (1 FPU/g and 0.25 IU/FPU, respectively) and short reaction times (10 h), SSF media containing 27.8 g of lactic acid/L were obtained with a volumetric productivity of 2.78 g/Lh. Material balances showed that the SSF processing of 100 kg of dry apple pomace results in the production of 36.6 kg of lactic acid, 18.3 kg of oligomeric carbohydrates (which can be used as ingredients for functional foods), 8.4 kg of microbial biomass, and 8 kg uronic acids.     

秸秆纤维素降解真菌QSH3-3的筛选及其特性研究

为了获得高效降解秸秆纤维素的微生物菌株,采用滤纸降解法和刚果红染色法从含纤维素类物质的土壤中筛选到一株产纤维素酶菌株QSH3-3,通过形态观察和ITS序列分析,鉴定为草酸青霉Penicillium oxalicum QSH3-3。摇瓶产酶试验结果表明,该菌株的最佳产酶条件为:碳源为0.5%的碱处理过的玉米秸秆粉,氮源为0.2% 硫酸铵,起始pH为7,接种量为5%,产酶温度为30℃,培养时间为4 d。最佳产酶条件下,滤纸酶（FPase）、内切酶（CMCase）和木聚糖酶（Xylanase）分别为12 U、33 U、605 U（U为酶活性单位）;在15℃,其残余酶活力可达70%～80%;在pH 4～9 范围内,其残余酶活力可达70%以上。酶学稳定性研究表明,FPase、CMCase和Xylanase在pH 4～9范围残余酶活力达85%以上,具有较强的酸碱适应能力;FPase、CMCase和Xylanase在45℃以上酶活力迅速下降,耐热性较差。该菌株具有较高的木聚糖酶活力以及较强的低温、pH的耐受力,因而该菌株在田间温差大、土壤偏碱性等复杂条件下对秸秆纤维素类物质的降解具有较高的应用潜力。     

Corncob-induced endo-1,4-beta-d-xylanase of Aspergillus oryzae MTCC 5154: production and characterization of xylobiose from glucuronoxylan

Eight different fungi were cultivated in a peptone-yeast extract medium containing 1% oat spelt xylan (OSX) to evaluate endo-1,4-beta-xylanase secretion for xylooligosaccharide (XOS) production. Aspergillus oryzae MTCC 5154, Aspergillus flavus , Aspergillus niger , and Aspergillus ochraceus showed significant titers of endoxylanases, which were further used for the production of XOS from birch wood xylan (BWX). A. oryzae produced 89.5 +/- 1.13% XOS in the hydrolysate at 24 h of reaction. The effect of OSX, BWX, and raw corncob on the induction of endoxylanase in A. oryzae was studied, and the xylanase activity was maximum at 96 h of cultivation in 3% corncob containing medium. XOS produced at 36 h of reaction was 5.87 +/- 0.53 mg/mL (12 +/- 2% xylose, 48 +/- 2.43% xylobiose, and 40 +/- 3.6% higher oligomers) from 1% BWX . HPLC/refractive index detection and ESI/MS analysis of fractions obtained by GPC corresponded to neutral and 4- O-methyl-alpha- d-glucuronic acid substituted acidic oligosaccharides. The major fraction, beta- d-xylopyranosyl-(1-->4)- d-xylanopyranose was characterized using (13)C NMR.     

黑曲霉固体发酵产木聚糖酶的响应面优化设计及其酶学性质的研究

本研究采用响应面法的中心组合对影响黑曲霉(aspergillus niger JL 15)固体发酵产木聚糖酶的条件进行了优化.以橘皮粉为基质,补充碳源、氮源,以及含水量和发酵时间对木聚糖酶产量具有显著影响(P<0.05).模拟二次多项式回归预测模型,并建立自变量与响应值的回归方程,获得各因素的最佳水平,即:甘油、硫酸铵的添加量分别为4.2%和3.1%,含水量为61%,发酵时间为73.4 h,木聚糖酶活性最大预测值达922.9 U/g干发酵产物,验证值为917.7 U/g干发酵产物,高出基础培养基酶活3.2倍.酶学性质分析研究表明,黑曲霉木聚糖酶(XylA)的最适温度和最适pH分别为55oC和pH 5.0.XylA的K_m和V_(max)值分别为9.24 mg/mL和54.05 μmol/min/mL.Mn~(2+)、Zn~(2+)和斗和Mg~(2+)对XylA活性具有促进作用,而Fe~(3+)和cu~(2+)对XylA活性具有明显抑制作用.HPLC分析结果表明,XylA的水解桦木木聚糖和麸皮不溶性木聚糖的产物均为木糖至木六糖,主要产物为木三糖.     

Immunoreactivity and amino acid content of fermented soybean products

Food allergy has become a public health problem that continues to challenge both the public and the food industry. The objective of this research was the detection and quantification of the major human allergenic soy proteins and to study the reduction in immunoreactivity and improvement of amino acid content after fermentation of soybean flour. Fermentation was carried out in the solid state of cracked seeds inoculated with Aspergillus oryzae, Rhizopus oryzae, and Bacillus subtilis and in the liquid state of milled soybean flours fermented naturally by microorganisms present only in the seeds or by inoculation with Lactobacillus plantarum. ELISA and Western blot were used to quantify IgE antibody response, and HPLC was used to identify and quantify total amino acids. L. plantarum fermented soy flour showed the highest reduction in IgE immunoreactivity (96-99%) depending upon the sensitivity of the plasma used. Among the solid fermented products, the lowest reduction in immunoreactivity was obtained when mold strains, R. oryzae and A. oryzae, were used (66 and 68%, respectively, for human plasma 97.5 kUA/L). Among the solid fermented products, those inoculated with B. subtilis yielded a 81 and 86% reduction in immunoreactivity against both human plasma 97.5 IgE kUA/L and human pooled plasma samples, respectively. When soybean was subjected to liquid fermentation, most of the total amino acids increased significantly ( p < or = 0.05). In solid fermentation with R. oryzae, only Ala and Thr content improved. Fermentation can decrease soy immunoreactivity, and there is potential of developing nutritious hypoallergenic soy products.     

Solid-substrate fermentation of corn fiber by Phanerochaete chrysosporium and subsequent fermentation of hydrolysate into ethanol

The goal of this study was to develop a fungal process for ethanol production from corn fiber. Laboratory-scale solid-substrate fermentation was performed using the white-rot fungus Phanerochaete chrysosporium in 1 L polypropylene bottles as reactors via incubation at 37 degrees C for up to 3 days. Extracellular enzymes produced in situ by P. chrysosporium degraded lignin and enhanced saccharification of polysaccharides in corn fiber. The percentage biomass weight loss and Klason lignin reduction were 34 and 41%, respectively. Anaerobic incubation at 37 degrees C following 2 day incubation reduced the fungal sugar consumption and enhanced the in situ cellulolytic enzyme activities. Two days of aerobic solid-substrate fermentation of corn fiber with P. chrysosporium, followed by anaerobic static submerged-culture fermentation resulted in 1.7 g of ethanol/100 g of corn fiber in 6 days, whereas yeast ( Saccharomyces cerevisiae) cocultured with P. chrysosporium demonstrated enhanced ethanol production of 3 g of ethanol/100 g of corn fiber. Specific enzyme activity assays suggested starch and hemi/cellulose contribution of fermentable sugar.     

Fermentation as a bio-process to obtain functional soybean flours

The effect of fermentation on the antioxidant compounds [vitamins C and E, total phenolic compounds (TPC), and reduced glutathione (GSH)], and antioxidant capacity [superoxide anion scavenging activity (SOD-like activity), peroxyl radical-trapping capacity (PRTC), inhibition of phosphatidylcholine (PC) peroxidation, and Trolox equivalent antioxidant capacity (TEAC)] of soybean (Glycine max cv. Merit) was studied. Fermentation was carried out in solid state in cracked seeds inoculated with Aspergillus oryzae, Rhizopus oryzae, Bacillus subtilis, and Lactobacillus plantarum and in liquid state either in cracked seeds or milled soybean flours fermented naturally by only the microorganisms present in the seeds or by inoculation with L. plantarum. Vitamin C was not detected in the studied samples. Fermentation caused a decrease in vitamin E activity, except when cracked seed was fermented with A. oryzae, R. oryzae, or B. subtilis that increased 31, 30, and 89%, respectively. Fermentation produced an increase in TPC content and did not affect or reduce the GSH content. Fermentation decreased SOD-like activity drastically, while PRTC increased except when it was carried out naturally in cracked seed. TEAC values rose sharply when soybeans were fermented with B. subtilis. Processed soybean extracts inhibited PC peroxidation in comparison with the control assay. On the basis of the results obtained, the relative contributions of vitamin E, TPC, and GSH to antioxidant capacity were calculated and results showed a very high TPC contribution and a low contribution of GSH and vitamin E activity. Optimum results for functional soybean flours were achieved when fermentation was carried out with B. subtilis inoculum.     

酒糟腐熟专用液态复合菌剂发酵条件研究

为制备酒糟腐熟复合微生物菌剂用于生产生物有机肥,对筛选得到的贝莱斯芽孢杆菌诱变育种菌株UN-5和里氏木霉的复合效果进行了考察。针对菌种耐酸性、复合时二者拮抗性以及培养时间、菌种配比和培养pH这3个影响复合菌剂纤维素酶活的主要因素设计单因素及正交实验。结果表明,复合菌剂的菌种配比、培养时间和pH对复合菌剂的纤维素酶活有显著影响。正交实验结果显示UN-5和里氏木霉制备复合菌剂的最佳条件为：培养时间28 h,菌种配比（UN-5∶里氏木霉）为2.5∶1,培养pH为5.0,此条件下制备的复合菌剂纤维素酶活达125.24 U,有效活菌数为10.3亿/g。     

Effect of Fractionation of Distillers Dried Grains With Solubles (DDGS) on Pelleting Characteristics of Broiler Diets

Recently, the Elusieve process, a combination of elutriation (air classification) and sieving (screening) was developed to separate fiber from distillers dried grains with solubles (DDGS) to increase DDGS utilization in nonruminant (poultry and swine) diets. Elusieve process produces three products: 1) Pan DDGS, with 5% higher protein content than conventional DDGS, which would be used at higher inclusion levels in broiler diets because of low fiber content; 2) Big DDGS, with nearly the same protein content as conventional DDGS, which would be used at same inclusion levels as conventional DDGS; and 3) Fiber product. The objective of this study was to determine and compare pellet‐mill throughput, power consumption, and pellet quality for broiler diets incorporating different levels (0, 10, and 20%) of conventional DDGS and DDGS products from Elusieve process. Poultry oil contents were lower (1.5–1.6%) in diets comprising Pan DDGS and diets without DDGS than in the other diets (2.2–3.1%). The feed throughput was not affected by inclusion levels or type of DDGS. Pellet quality (pellet durability index [PDI]) for diets comprising Pan DDGS (both 10 and 20% inclusion levels) was significantly better than PDI for diets comprising conventional DDGS, Big DDGS, and the diet without DDGS. Better pellet quality of diets comprising Pan DDGS could be due to lower quantity of poultry oil used as well as compositional characteristics such as low fiber and high protein. Diets with Big DDGS had similar pelleting characteristics to those with conventional DDGS. Pellet quality deteriorated at higher inclusion levels of conventional DDGS, Big DDGS, and Enhanced DDGS. Considering that Pan DDGS would be included at higher inclusion levels in broiler diets, superior pellet quality of diets comprising Pan DDGS is beneficial.     

甘薯渣同步糖化发酵生产酒精的工艺优化

为了综合利用甘薯淀粉工业废渣,本研究以甘薯渣为原料发酵生产酒精,并对其同步糖化发酵工艺(SSF)进行优化。研究同步糖化发酵时影响酒精发酵工艺的9个因素,采用Plackett-Burman试验设计筛选出显著因素,并在筛选结果的基础上,用最陡爬坡途径逼近最大响应区域,然后利用响应面分析法确定其最佳参数。结果表明,影响酒精发酵工艺的显著因素为糖化酶、接种量和发酵温度。酒精发酵优化最佳参数为:α-淀粉酶8U/g,液化时间1.5h,液化温度90℃,硫酸铵质量分数0.15g/100g,pH值4,发酵时间36h,糖化酶151U/g,接种量0.3%,发酵温度36℃。在此条件下,验证试验得到的酒精体积分数达到17.15%,接近理论预测值16.95%。优化后的工艺可为甘薯渣同步糖化发酵生产酒精提供技术参考。     

蛋白原料及其混合粉料理化性质对颗粒饲料加工质量的影响

该研究旨在探究豆粕、棉粕、菜粕、酒糟蛋白(Distillers Dried Grains with Solubles,DDGS)、乙醇梭菌蛋白5种蛋白原料及其混合粉料的营养指标和理化性质的差异,确定影响颗粒饲料质量和制粒能耗的关键指标,对5种蛋白原料的制粒效果进行综合评价。以豆粕为对照组,仅改变蛋白原料,采用相同的加工参数制备颗粒饲料,比较不同蛋白原料的制粒效果,进行主成分分析及偏最小二乘回归分析(Partial Least Squares Regression,PLS)。结果表明:在原料营养指标和理化特性方面,乙醇梭菌蛋白具有高蛋白含量、高蛋白溶解度、低脂肪、低纤维的特点,棉粕具有高纤维的特点,菜粕具有高纤维和低蛋白溶解度的特点,DDGS具有低蛋白和高脂肪的特点。蛋白原料吸水性强弱排列顺序为乙醇梭菌蛋白、豆粕、棉粕、菜粕、DDGS,水溶性与之相反。乙醇梭菌蛋白组和棉粕组的制粒能耗较高,豆粕组的制粒能耗最低;棉粕组和乙醇梭菌蛋白组的修正耐久性(Modified Pellet Durability Index,MPDI)较高分别为92.72%和90.57%,菜粕组的MPDI最低为79.68%;乙醇梭菌蛋白组的硬度最高为130.95N,DDGS组的硬度最低为74.26N;乙醇梭菌蛋白组的糊化度最高为45.56%,DDGS组的糊化度最低为31.36%。通过偏最小二乘回归模型得到,蛋白含量、蛋白溶解度和吸水性的增加会提高颗粒饲料硬度、PDI和MPDI;粗纤维含量、蛋白溶解度和吸水性的增加会增加制粒能耗。综合分析5种蛋白原料制粒特性,由高到低排序为乙醇梭菌蛋白、棉粕、豆粕、菜粕、DDGS。研究结果为实际生产颗粒饲料时蛋白原料的选择提供参考依据。     

蒸汽爆破预处理和微生物发酵对玉米秸秆降解率的影响

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。     

降解玉米秸秆真菌复合菌系的构建及其降解效果评价

  【目的】  秸秆的木质纤维素含量丰富、结构复杂，在自然界中降解较慢，增加秸秆降解菌剂中菌株的多样性有利于提升还田秸秆的降解效果。探究菌株多样性水平和组成影响复合菌系秸秆降解的效果及原因，为复合菌系在秸秆降解中的应用提供理论支撑。  【方法】  通过富集驯化培养，从玉米秸秆还田土壤中筛选具有秸秆降解能力的真菌，从中挑选5株高效秸秆降解真菌进行基因间隔区序列 (ITS) 测定和物种鉴定，明确其分类地位。通过全组合构建菌株多样性为1～5的复合菌系，分别检测复合菌系的秸秆相对降解率及其滤纸酶、纤维素内切酶和木聚糖酶活性，利用方差分析和相关性分析等方法研究菌株多样性和组成对复合菌系玉米秸秆降解效果及其纤维素酶活性的影响。  【结果】  共筛选获得了15株具有秸秆降解能力的真菌，其中5株真菌的秸秆降解效果好、纤维素水解能力强。经ITS序列鉴定和系统发育分析，发现5株降解真菌的遗传差异较大，Z7-6、F7-5、F4-3、L1-1和J2-5分别与草酸青霉 (Z7-6: Penicillium oxalicum)、烟曲霉 (F7-5: Aspergillus fumigatus)、哈茨木霉 (F4-3: Trichoderma harzianum)、白囊耙齿菌 (L1-1: Irpex lacteus) 和木贼镰刀菌 (J2-5: Fusarium equiseti) 的ITS序列相似度均超过99.95%。全组合复配结果表明，复合菌系的秸秆降解能力和纤维素酶活力均高于各单一菌株，且随着菌株多样性水平的增加而提高。滤纸酶、纤维素内切酶和木聚糖酶的活力越强，复合菌系对玉米秸秆的降解效果越好，而其秸秆相对降解率主要取决于滤纸酶和纤维素内切酶的活性。抽样效应分析发现，不同菌株对复合菌系的秸秆降解效果、滤纸酶和纤维素内切酶活性的影响不同。不含菌株F7-5的复合菌系降解效果显著优于含有该菌株的组合，以Z7-6 (P. oxalicum)、F4-3 (T. harzianum)、L1-1 (I. lacteus) 和J2-5 (F. equiseti) 组合F1的玉米秸秆降解效果最佳、酶活性最高。  【结论】  秸秆降解复合菌系的构建过程需要同时考虑多样性效应和抽样效应，增加降解菌的多样性有助于增强秸秆的降解效果。本研究筛选获得的复合菌系F1在玉米秸秆降解中具有潜在的应用前景。     

大豆/玉米间作体系中接种AM真菌和根瘤菌对氮素吸收的促进作用

利用大豆和玉米之间根系不同分隔方式的盆栽试验,研究了在玉米/大豆间作体系中接种大豆根瘤菌、AM真菌Glomus mosseae和双接种对间作体系氮素吸收的促进作用。结果表明,双接种处理显著提高了大豆及与其间作玉米的生物量、氮含量,双接种大豆/玉米间作体系总吸氮量比单接AM菌根、根瘤菌和不接种对照平均分别增加22.6%、24.0%和54.9%。大豆促进了与其间作玉米对氮素的吸收作用,在接种AM真菌和双接种条件,间作玉米的AM真菌侵染率提高,大豆根瘤数增加; 接种AM真菌处理,不分隔和尼龙网分隔比完全分隔玉米吸氮量的净增加量是未接种对照的1.8、2.6倍,双接种处理分别是对照的1.3和1.7倍。说明在间作体系中进行有效的根瘤菌和AM真菌接种,发挥两者的协同作用对提高间作体系土壤养分利用效率,进一步提高间作体系的生产力有重要的意义。     

Cellulase complex in a tomato field soil: Induction,localization and some properties

A soil sample from a tomato field showed cellulase activity after 1 week of storage but showed no cellulase activity when stored for 1 yr. Addition of cellulose and inoculation with untreated soil induced cellulase activity in remoistened, heated soil. Selective inhibition of bacteria or fungal growth in the incubated soil indicated that fungi were the more important source of cellulase in this soil. Over 60% of the isolates tested, showed cellulolytic activity on CMC-agar. Although organic debris was a minor component in the soil sample, most of the cellulase activity was localized in this fraction. Cellulase activity was extracted with 0.1 m phosphate buffer (pH 7), but not with distilled water. The activity of the extract ' was lost on keeping at 80°C for 10 min and was optimal at pH 5. The extract hydrolyzed either soluble or insoluble substrate.     

Separation of Fiber from Distillers Dried Grains with Solubles (DDGS) Using Sieving and Elutriation

A process was developed to separate fiber from distillers dried grains with solubles (DDGS) in a dry‐grind corn process. Separation of fiber from DDGS would provide two valuable coproducts: 1) DDGS with reduced fiber, increased fat, and increased protein contents; and 2) fiber. The process, called elusieve process, used two separation methods, sieving and elutriation, to separate the fiber. Material carried by air to the top of the elutriation column was called the lighter fraction and material that settled to the bottom of the column was called the heavier fraction. We evaluated the compositions of fractions produced from sieving and elutriation. Two commercial samples of DDGS were obtained from two dry‐grind corn plants. Sieving over four screens (869, 582, 447, and 234 μm openings) created five size categories. The two smallest size categories contained >40% (w/w) of the original DDGS and had reduced fiber and increased protein and fat contents relative to the original DDGS. Elutriation of the remaining three size categories increased protein and fat contents and reduced fiber contents in the heavier fractions. Elutriation at air velocities of 1.59–5.24 m/sec increased the protein content of the heavier fraction by 13–41% and increased the fat content of the heavier fraction by 4–127% compared with the bulk fractions of each size category. This process was effective in separating fiber from both DDGS samples evaluated. Elusieve process does not require changes in the existing dry‐grind process and can be implemented at the end of the dry‐grind process.     

Economics of Fiber Separation from Distillers Dried Grains with Solubles (DDGS) Using Sieving and Elutriation

Separation of fiber from distillers dried grains with solubles (DDGS) provides two valuable coproducts: 1) enhanced DDGS with reduced fiber, increased fat and increased protein contents and 2) fiber. Recently, the elusieve process, a combination of sieving and elutriation was found to be effective in separating fiber from two commercial samples of DDGS (DDGS‐1 and DDGS‐2). Separation of fiber decreased the quantity of DDGS, but increased the value of DDGS by increasing protein content and produced a new coproduct with higher fiber content. Economic analysis was conducted to determine the payback period, net present value (NPV), and internal rate of return (IRR) of the elusieve process. The dependence of animal foodstuff prices on their protein content was determined. Equipment prices were obtained from industrial manufacturers. Relative to crude protein content of original DDGS, crude protein content of enhanced DDGS was higher by 8.0% for DDGS‐1 and by 6.3% for DDGS‐2. For a dry‐grind plant processing corn at the rate of 2,030 metric tonnes/day (80,000 bushels/day), increase in revenue due to the elusieve process would be $0.4 to 0.7M/year. Total capital investment for the elusieve process would be $1.4M and operating cost would be $0.1M/year. Payback period was estimated to be 2.5–4.6 years, NPV was $1.2–3.4M, and IRR was 20.5–39.5%.     

甜高粱茎汁及茎渣同步糖化发酵工艺优化

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。