Fate of Fumonisin B1 in Naturally Contaminated Corn during Ethanol Fermentation

Two lots of corn naturally contaminated with fumonisin B₁ (15 and 36 ppm) and a control lot (no fumonisin B₁ detected) were used as substrates for ethanol production in replicate 8.5-liter yeast fermentations. Ethanol yields were 8.8% for both the control and low-fumonisin corn, while the high-fumonisin corn contained less starch and produced 7.2% ethanol. Little degradation of fumonisin occurred during fermentation, and most was recovered in the distillers' grains, thin stillage, and distillers' solubles fractions. No toxin was detected in the distilled alcohol or centrifuge solids. Ethanol fermentation of fumonisin-contaminated corn coupled with effective detoxification of distillers' grains and aqueous stillage is suggested as a practical process strategy for salvaging contaminated corn.     

High ethanol yields using Aspergillus oryzae koji and corn media

Summary High ethanol and stillage solids have been achieved using whole corn mashes. Ethanol yields of 14% (v/v) (89.5% of theory) and stillage levels of approximately 23% (w/v) were obtained in 74–90 hours using mild acid pretreatment with Aspergillus oryzae wheat bran koji saccharification. High ethanol yields were also obtained with bacterial amylase, instead of the acid treatment, when the sterilization step was omitted. The implications of ethanol fermentation process modifications are explored.     

Impact of recycling stillage on conversion of dilute sulfuric acid pretreated corn stover to ethanol

Both the current corn starch to ethanol industry and the emerging lignocellulosic biofuels industry view recycling of spent fermentation broth or stillage as a method to reduce fresh water use. The objective of this study was to understand the impact of recycling stillage on conversion of corn stover to ethanol. Sugars in a dilute‐acid pretreated corn stover hydrolysate were fermented to ethanol by the glucose–xylose fermenting bacteria Zymomonas mobilis 8b. Three serial fermentations were performed at two different initial sugar concentrations using either 10% or 25% of the stillage as makeup water for the next fermentation in the series. Serial fermentations were performed to achieve near steady state concentration of inhibitors and other compounds in the corn stover hydrolysate. Little impact on ethanol yields was seen at sugar concentrations equivalent to pretreated corn stover slurry at 15% (w/w) with 10% recycle of the stillage. However, ethanol yields became progressively poorer as the sugar concentration increased and fraction of the stillage recycled increased. At an equivalent corn stover slurry concentration of 20% with 25% recycled stillage the ethanol yield was only 5%. For this microorganism with dilute‐acid pretreated corn stover, recycling a large fraction of the stillage had a significant negative impact on fermentation performance. Although this finding is of concern for biochemical‐based lignocellulose conversion processes, other microorganism/pretreatment technology combinations will likely perform differently. Biotechnol. Bioeng. 2010;105: 992–996. © 2009 Wiley Periodicals, Inc.     

Economic analysis of a modified dry grind ethanol process with recycle of pretreated and enzymatically hydrolyzed distillers' grains

A modification of the conventional dry grind process for producing ethanol from yellow dent corn is considered with respect to its economic value. Process modifications include recycling distillers' grains, after being pretreated and hydrolyzed, with the ground corn and water to go through fermentation again and increase ethanol yields from the corn starch. A dry grind financial model, which has been validated against other financial models in the industry, is utilized to determine the financial impact of the process changes. The hypothesis was that the enhanced process would yield higher revenues through additional ethanol sales, and higher valued dried distillers' grains (DDGS), due to its higher protein content, to mitigate the drop in DDGS yields. A 32% increase in net present value (NPV) for the overall operation is expected when applying the process modifications to a 100million gallon ethanol plant, and an enzyme cost of $0.20 for each additional gallon of ethanol produced. However, there may be no value added to the enhanced dried distillers' grains (eDDGS), even in light of its higher protein levels, as current pricing is expected to be more sensitive to the amino acid profile than the total protein level, and the eDDGS has lower lysine levels, a key amino acid. Thus, there is a decrease in revenue from eDDGS due to the combination of no price change and loss of DDGS yield to ethanol. The financial improvements are a result of the increased revenue from higher ethanol yields outpacing the sum of all added costs, which include higher capital costs, larger loan payments, increased operating costs, and decreased revenues from dried distillers' grains.     

Process simulation of modified dry grind ethanol plant with recycle of pretreated and enzymatically hydrolyzed distillers' grains

Distillers' grains (DG), a co-product of a dry grind ethanol process, is an excellent source of supplemental proteins in livestock feed. Studies have shown that, due to its high polymeric sugar contents and ease of hydrolysis, the distillers' grains have potential as an additional source of fermentable sugars for ethanol fermentation. The benefit of processing the distillers' grains to extract fermentable sugars lies in an increased ethanol yield without significant modification in the current dry grind technology. Three different potential configurations of process alternatives in which pretreated and hydrolyzed distillers' grains are recycled for an enhanced overall ethanol yield are proposed and discussed in this paper based on the liquid hot water (LHW) pretreatment of distillers' grains. Possible limitations of each proposed process are also discussed. This paper presents a compositional analysis of distillers' grains, as well as a simulation of the modified dry grind processes with recycle of distillers' grains. Simulated material balances for the modified dry grind processes are established based on the base case assumptions. These balances are compared to the conventional dry grind process in terms of ethanol yield, compositions of its co-products, and accumulation of fermentation inhibitors. Results show that 14% higher ethanol yield is achievable by processing and hydrolyzing the distillers' grains for additional fermentable sugars, as compared to the conventional dry grind process. Accumulation of fermentation by-products and inhibitory components in the proposed process is predicted to be 2-5 times higher than in the conventional dry grind process. The impact of fermentation inhibitors is reviewed and discussed. The final eDDGS (enhanced dried distillers' grains) from the modified processes has 30-40% greater protein content per mass than DDGS, and its potential as a value-added process is also analyzed. While the case studies used to illustrate the process simulation are based on LHW pretreated DG, the process simulation itself provides a framework for evaluation of the impact of other pretreatments.     

Farm-scale production of fuel ethanol and wet grain from corn in a batch process

The batch production of fuel grade ethanol and distillers' wet grain (wet solids) in a farm-scale process (1240-15,580 L/batch) is described. The employs yeast fermentation of amylase-treated corn mash and a two-stage distillation. Primary emphasis in this study was on the cooking, fermentation, and centrifugation steps. Without recycling, fermentation of the mash yield beers with 10.0-10.5% ethanol. Recycling of stillage supernatant at full, 75, or 50% strengths produced enriched mashes that after 48-h fermentation yielded beers with 5-;14% more ethanol. Recycling twice with full-strength supernatant at pH 7.0 increased the ethanol yield in the final beer 16.5%; however, the time to complete the final fermentation was extended form 48 to 72 h and salt buildup occurred. By recycling at pH 5.4, it was possible to avoid rapids salt buildup and obtain beers with 10.3-10.5% ethanol. Recycling resulted in increased levels of glucose, starch, crude protein, and fat in the beer and a reduced moisture content while the wet solids showed an increased starch content. Centrifugation after cooking or fermentation yield in the subsequently produced beer. Fermentation of a volume-resorted mash supernatant gave a beer with only 9.25% ethanol. Mash wet solids varied somewhat chemically from beer and stillage solids. An economic and energy balance analysis of various modes of plant operation are provided and plant considerations are suggested.     

Natural occurrence of the C series of fumonisins in moldy corn

We analyzed 44 moldy corn samples for the B and C series of fumonisins by high-performance liquid chromatography. Of the 44 samples, 32 (73%) were contaminated with both the B and C series of fumonisins and 6 were contaminated with only the B series of fumonisins. The incidence of fumonisin C1 in moldy corn was 71%; the incidence was 11% for fumonisin C3 and 43% for fumonisin C4. Their mean levels ranged from 500 to 1,900 ng/g. This is the first report on the natural occurrence of the C series of fumonisins and fumonisin B4 in moldy corn.     

Changes in mineral concentrations and phosphorus profile during dry-grind processing of corn into ethanol

For determining variation in mineral composition and phosphorus (P) profile among streams of dry-grind ethanol production, samples of ground corn, intermediate streams, and distillers dried grains with solubles (DDGS) were obtained from three commercial plants. Most attributes (dry matter concentrations) increased significantly from corn to cooked slurry but fermentation caused most significant increase in all attributes. During centrifugation, more minerals went into thin stillage than wet grains, making minerals most concentrated in the former. Mineral increase in DDGS over corn was about 3 fold, except for Na, S, Ca, and Fe. The first three had much higher fold of increase, presumably due to exogenous addition. During fermentation, phytate P and inorganic P had 2.54 and 10.37 fold of increase over corn, respectively, while relative to total P, % phytate P decreased and % inorganic P increased significantly. These observations suggest that phytate underwent some degradation, presumably due to activity of yeast phytase.     

New technologies in value addition to the thin stillage from corn-to-ethanol process

Grain-to-ethanol production has increased steadily in the United States in the past few decades, which resulted in remarkable records in the availability of co-products. Dry-grind is the most common method of ethanol production worldwide, which concentrates the corn and yeast nutrients in the downstream operations. The ethanol co-products have traditionally been a commodity for livestock feed as they contain desirable nutrients, mostly sold as distiller’s grains. The liquid fraction produced after the centrifugation of the bottoms of the ethanol rectifying and distilling operations is named thin stillage, produced at volumes several times greater than those of ethanol. A portion of thin stillage is normally recycled as backset water, while the remaining goes through a series of evaporations. Evaporating a large amount of water from thin stillage is an energy-consuming process and recycling the thin stillage may lead to the accumulation of nutrients in co-products in distiller’s grains. There are several other industrial processes to utilize thin stillage, such as oil extraction, anaerobic digestion, and secondary fermentation. Recently, promising results have been reported on the production of important commodity chemicals, extracting high-value products, and energy production from thin stillage. This review provides an overview on the new processes and products via valorization of thin stillage by innovative technologies that are being currently developed. The new applications of thin stillage discussed in this review could open new opportunities for the ethanol plants and ethanol researchers by increasing the revenue and simultaneously reducing negative environmental impacts of ethanol production.     

Processing cereal grains,thin stillage,and cheese whey to fuel ethanol in a farm-scale plant

Hydrous fuel ethanol (95%) and distiller's wet grain (DWG) were produced in a farm-scale plant (< 4 million liters ethanol year⁻¹) from corn, wheat, and grain sorghum particles of various sizes, from corn combined with thin stillage-whey, and from various other cereal grains. These variations were made in a search to find the best set of conditions for maximizing the energy balance (energy output divided by energy input) and minimizing the cost of ethanol production. We found that the optimum hammermill screen size for corn, wheat, and grain sorghum was 1·59–2·38 mm. In tests with thin stillage and whey a higher energy balance (2·91) occurred when one part whey was mixed with three parts stillage, rather than the reverse (2·69). However, the reverse (three parts whey and one part stillage) gave a lower ethanol cost ($0.45 liter⁻¹) than the original ($0.47 liter⁻¹). Tests with various cereal grains (corn, oats, wheat, barley, rye, and grain sorghum) gave identical energy balance values (2·26) when 10% (v/v) ethanol beers were produced. However, rye ($0.50 liter⁻¹), grain sorghum ($0.46 liter⁻¹), and corn ($0.51 liter⁻¹) yielded ethanol at the lowest net cost. Recommendations for farm-scale plants are also provided.     

废糟液全循环条件下絮凝酵母乙醇连续发酵

丙酸是以玉米为原料自絮凝酵母乙醇连续发酵系统废糟液全循环过程中积累的主要抑制物。基于丙酸对酵母细胞抑制机理,开发了3种废糟液全循环条件下乙醇连续发酵工艺策略。首先根据高温导致丙酸生成的现象,去除了物料灭菌环节,使发酵液丙酸浓度显著降低,生物量和乙醇浓度分别提高了59.3%和7.4%。其次,以丙酸浓度达到半数抑制浓度(IC50)40 mmol/L为目标,通过拟合丙酸积累数据预测废糟液全循环的最长运行时间,发酵装置运行应控制在此时间范围内。再次,较低的环境pH值提高了丙酸毒性,而实验证明发酵液pH为5.5时,丙酸对细胞生长的抑制影响最小,因此控制发酵过程中的pH有利于弱化丙酸毒性。     

Studies on extraction of fumonisins from rice, corn-based foods and beans

Different solvent mixtures were examined for extraction of fumonisins from various naturally contaminated and spiked foods and foodstuffs: rough rice, retail rice, rice flour, white corn flour, corn meal, corn starch, corn flakes, tortilla/corn chips, white bean flour, white beans, mung beans, adzuki beans and infant cereals. Most of the naturally contaminated samples were analyzed using the extraction solvent mixtures methanol-acetonitrile-water (25:25:50) (solvent A) and methanol-water (75:25 or 80:20) (solvents B, BB); some were extracted with 0.1 M sodium hydrogen phosphate-acetonitrile (1:1, adjusted to pH 3.0 with o-phosphoric acid) (solvent C) and methanol-0.025 M borate buffer (3:1, adjusted to pH 9.2 with 1 N sodium hydroxide) (solvent D). A 1-ml SAX solid phase extraction column was used for the cleanup in all cases except for infant cereals, for which immunoaffinity chromatography was used; fumonisin concentrations were determined by liquid chromatography. Solvent A gave slightly better extraction of fumonisins from one of two samples of naturally contaminated rough rice than solvent B (fumonisin B₁: 4080 ng/g versus 3150 ng/g; fumonisin B₂:1100 ng/ g versus 922 ng/g) and much better extraction than solvent C (1210 ng/g fumonisin B₁ and 315 ng/g fumonisin B₂) or solvent D (372 ng/ g fumonisin B1 and 191 ng/g fumonisin B2). However, spike recoveries on a similar rice naturally contaminated at a lower level were only in the 43–53% range (solvent A). Recovery of fumonisins was very poor from spiked white rice flour but satisfactory from other rice foods. Solvent A similarly gave slightly better extraction of fumonisins from a sample of naturally contaminated white corn flour than solvent B (fumonisin B₁ 1260 ng/g versus 931 ng/g; fumonisin B₂: 511 ng/g versus 447 ng/g ) and better extraction than solvents C and D. Solvent A was also a better solvent for extraction of fumonisins from naturally contaminated tortilla chips and infant cereals. Study of naturally contaminated corn starch was confounded by instability of fumonisins in this food. Recovery of fumonisins from spiked corn meal, tortilla chips, corn flakes, various types of beans and infant cereals with solvent A and/or solvent B (or BB) was satisfactory.     

Thin stillage fractionation using ultrafiltration: resistance in series model

The corn based dry grind process is the most widely used method in the US for fuel ethanol production. Fermentation of corn to ethanol produces whole stillage after ethanol is removed by distillation. It is centrifuged to separate thin stillage from wet grains. Thin stillage contains 5–10% solids. To concentrate solids of thin stillage, it requires evaporation of large amounts of water and maintenance of evaporators. Evaporator maintenance requires excess evaporator capacity at the facility, increasing capital expenses, requiring plant slowdowns or shut downs and results in revenue losses. Membrane filtration is one method that could lead to improved value of thin stillage and may offer an alternative to evaporation. Fractionation of thin stillage using ultrafiltration was conducted to evaluate membranes as an alternative to evaporators in the ethanol industry. Two regenerated cellulose membranes with molecular weight cut offs of 10 and 100 kDa were evaluated. Total solids (suspended and soluble) contents recovered through membrane separation process were similar to those from commercial evaporators. Permeate flux decline of thin stillage using a resistance in series model was determined. Each of the four components of total resistance was evaluated experimentally. Effects of operating variables such as transmembrane pressure and temperature on permeate flux rate and resistances were determined and optimum conditions for maximum flux rates were evaluated. Model equations were developed to evaluate the resistance components that are responsible for fouling and to predict total flux decline with respect to time. Modeling results were in agreement with experimental results (R ² > 0.98).     

Stillage backset and its impact on ethanol fermentation by the flocculating yeast

The second largest cost in fuel ethanol production is from energy consumption with ethanol distillation and stillage treatment, particularly when stillage is treated by the multi-evaporation process. Therefore, stillage backset is the most economically competitive strategy for reducing discharge and saving energy consumption. In this article, continuous ethanol fermentation was performed by the flocculating yeast under stillage backset conditions. Compared to regular yeast, immobilized yeast within the fermentor through flocculation reduced byproducts formation in the stillage, since heat lysis of yeast during ethanol distillation was prevented, and many side reactions were thus eliminated, making more stillage backset within the fermentation system possible. Although pyruvic acid, succinic acid, citric acid, α-ketoglutaric acid, fumaric acid and glycerol from yeast metabolism, furfural and 5-hydroxymethyl furfural from process operations, and acetic acid and lactic acid from slight contamination were accumulated with the stillage backset, they had no significant impact on yeast growth and ethanol fermentation due to low concentrations accumulated within the fermentation system. However, propionic acid that was generated mainly during hydrolysate sterilization and distillation of the fermentation broth was detected as the major inhibitor, but this byproduct would be significantly reduced under industrial conditions without hydrolysate sterilization, making the stillage backset more reliable for industrial application.     

Fumonisin B1 production by Fusarium species other than F. moniliforme in section Liseola and by some related species.

Strains of Fusarium proliferatum, F. subglutinans, F. anthophilum, F. annulatum, F. succisae, F. beomiforme, F. dlamini, F. napiforme, and F. nygamai from a variety of substrates and geographic areas were tested for the production of fumonisin B1 in culture. None of the cultures of F. subglutinans (0 of 23), F. annulatum (0 of 1), F. succisae (0 of 2), or F. beomiforme (0 of 15) produced fumonisin B1 in culture. Strains of F. proliferatum (19 of 31; 61%) produced fumonisin B1 in amounts ranging from 155 to 2,936 ppm, strains of F. anthophilum (3 of 17; 18%) produced fumonisin B1 in amounts ranging from 58 to 613 ppm, strains of F. dlamini (5 of 9; 56%) produced fumonisin B1 in amounts ranging from 42 to 82 ppm, strains of F. napiforme (5 of 33; 15%) produced fumonisin B1 in amounts ranging from 16 to 479 ppm, and strains of F. nygamai (10 of 27; 37%) produced fumonisin B1 in amounts ranging from 17 to 7,162 ppm. Of the species tested, F. proliferatum is the most important producer of fumonisin B1 because of its association with corn and animal mycotoxicoses such as porcine pulmonary edema. F. napiforme and F. nygamai also may be important because of their association with the food grains millet and sorghum. At present, F. anthophilum and F. dlamini are of minor importance because they are not associated with corn or other major food grains and have only a limited geographic range. This is the first report of the production of fumonisins by F. anthophilum, F. dlamini, and F. napiforme.     

Fumonisin B1 production by Fusarium species other than F. moniliforme in section Liseola and by some related species.

Strains of Fusarium proliferatum, F. subglutinans, F. anthophilum, F. annulatum, F. succisae, F. beomiforme, F. dlamini, F. napiforme, and F. nygamai from a variety of substrates and geographic areas were tested for the production of fumonisin B1 in culture. None of the cultures of F. subglutinans (0 of 23), F. annulatum (0 of 1), F. succisae (0 of 2), or F. beomiforme (0 of 15) produced fumonisin B1 in culture. Strains of F. proliferatum (19 of 31; 61%) produced fumonisin B1 in amounts ranging from 155 to 2,936 ppm, strains of F. anthophilum (3 of 17; 18%) produced fumonisin B1 in amounts ranging from 58 to 613 ppm, strains of F. dlamini (5 of 9; 56%) produced fumonisin B1 in amounts ranging from 42 to 82 ppm, strains of F. napiforme (5 of 33; 15%) produced fumonisin B1 in amounts ranging from 16 to 479 ppm, and strains of F. nygamai (10 of 27; 37%) produced fumonisin B1 in amounts ranging from 17 to 7,162 ppm. Of the species tested, F. proliferatum is the most important producer of fumonisin B1 because of its association with corn and animal mycotoxicoses such as porcine pulmonary edema. F. napiforme and F. nygamai also may be important because of their association with the food grains millet and sorghum. At present, F. anthophilum and F. dlamini are of minor importance because they are not associated with corn or other major food grains and have only a limited geographic range. This is the first report of the production of fumonisins by F. anthophilum, F. dlamini, and F. napiforme.     

Conversion of corn milling fibrous co-products into ethanol by recombinant Escherichia coli strains K011 and SL40

Corn hulls and corn germ meal were both evaluated as feedstocks for production of ethanol for biofuel. Currently, these fibrous co-products are combined with corn steep liquor and the fermentation bottoms (if available) and marketed as cattle feed. Samples were obtained from wet and dry corn mills. The corn hulls and germ meal were evaluated for starch and hemicellulose compositions. Starch contents were 12 to 32% w/w and hemicellulose (arabinoxylans) contents were 23 to 64% w/w. Corn fibrous samples were hydrolysed, using dilute sulphuric acid, into mixed sugar streams containing arabinose, glucose and xylose. Total sugar concentrations in the hydrolysate varied from 8.4 to 10.8% w/v. The hydrolysates were fermented to ethanol using recombinant E. coli strains K011 and SL40. Ethanol yields were 0.38 to 0.41g ethanol produced/g total sugars consumed and fermentations were completed in 60h or less. However, residual xylose was detected for each hydrolysate fermentation and was especially significant for fermentations using strain SL40. Strain K011 was a superior ethanologenic strain compared with strain SL40 in terms of both ethanol yield and maximum productivity.     

Composition of corn dry-grind ethanol by-products: DDGS, wet cake, and thin stillage

DDGS and wet distillers' grains are the major co-products of the dry grind ethanol facilities. As they are mainly used as animal feed, a typical compositional analysis of the DDGS and wet distillers' grains mainly focuses on defining the feedstock's nutritional characteristics. With an increasing demand for fuel ethanol, the DDGS and wet distillers' grains are viewed as a potential bridge feedstock for ethanol production from other cellulosic biomass. The introduction of DDGS or wet distillers' grains as an additional feed to the existing dry grind plants for increased ethanol yield requires a different approach to the compositional analysis of the material. Rather than focusing on its nutritional value, this new approach aims at determining more detailed chemical composition, especially on polymeric sugars such as cellulose, starch and xylan, which release fermentable sugars upon enzymatic hydrolysis. In this paper we present a detailed and complete compositional analysis procedure suggested for DDGS and wet distillers' grains, as well as the resulting compositions completed by three different research groups. Polymeric sugars, crude protein, crude oil and ash contents of DDGS and wet distillers' grains were accurately and reproducibly determined by the compositional analysis procedure described in this paper.     

Effect of corn preparation methods on dry-grind ethanol production by granular starch hydrolysis and partitioning of spent beer solids

Two corn preparation methods, rollermill flaking and hammermill grinding, were compared for efficient processing of corn into ethanol by granular starch hydrolysis and simultaneous fermentation by yeast Saccharomyces cerevisiae. Corn was either ground in a hammermill with different size screens or crushed in a smooth-surfaced rollermill at different roller gap settings. The partitioning of beer solids and size distribution of solids in the thin stillage were compared. The mean particle diameter d₅₀ for preparations varied with set-ups and ranged between 210 and 340 μm for ground corn, and 1180-1267 μm for flaked corn. The ethanol concentrations in beer were similar (18-19% v/v) for ground and flaked preparations, however, ethanol productivity increased with reduced particle size. Roller versus hammermilling of corn reduced solids in thin stillage by 28%, and doubled the volume percent of fines (d₅₀ ∼ 7 μm)in thin stillage and decreased coarse (d₅₀ ∼ 122 μm) by half compared to hammermilling.     

Fate of virginiamycin through the fuel ethanol production process

Antibiotics are frequently used to prevent and treat bacterial contamination of commercial fuel ethanol fermentations, but there is concern that antibiotic residues may persist in the distillers grains coproducts. A study to evaluate the fate of virginiamycin during the ethanol production process was conducted in the pilot plant facilities at the National Corn to Ethanol Research Center, Edwardsville, IL. Three 15,000-liter fermentor runs were performed: one with no antibiotic (F1), one dosed with 2 parts per million (ppm) of a commercial virginiamycin product (F2), and one dosed at 20 ppm of virginiamycin product (F3). Fermentor samples, distillers dried grains with solubles (DDGS), and process intermediates (whole stillage, thin stillage, syrup, and wet cake) were collected from each run and analyzed for virginiamycin M and virginiamycin S using a liquid chromatography-mass spectrometry method. Virginiamycin M was detected in all process intermediates of the F3 run. On a dry-weight basis, virginiamycin M concentrations decreased approximately 97 %, from 41 μg/g in the fermentor to 1.4 μg/g in the DDGS. Using a disc plate bioassay, antibiotic activity was detected in DDGS from both the F2 and F3 runs, with values of 0.69 μg virginiamycin equivalent/g sample and 8.9 μg/g, respectively. No antibiotic activity (<0.6 μg/g) was detected in any of the F1 samples or in the fermentor and process intermediate samples from the F2 run. These results demonstrate that low concentrations of biologically active antibiotic may persist in distillers grains coproducts produced from fermentations treated with virginiamycin.