Oil Recovery from Dry Grind Ethanol Plant Coproducts Using Ethanol

Corn ethanol bio-refineries are seeking economic processing strategies for recovering oil from their coproducts. The addition of ethanol can be an efficient method to recover the oil from the coproducts as the industry has available ethanol. This study considered the effects of ethanol on oil recovery from distillers’ dried grains with solubles (DDGS) and oil partitioning from whole stillage (WS) on a laboratory scale. Ethanol was added with original and heavier fraction DDGS in different temperatures (room temperature ~20 °C, 30 °C, 40 °C, and 50 °C) and solids loadings (20%, 30%, and 40%), and their effects on oil recovery were evaluated. The whole stillage was incubated with ethanol at room temperature (~20 °C) and 50 °C separately to analyze WS’s oil distribution in the liquid and solid phases. The amount of recovered oil from the original and heavier fractions of DDGS varies from 25–45% and 45–70%, respectively, with an increment of temperature. Increasing solids loadings up to 30% had no effect on oil recovery from either DDGS sample. Ethanol treatment in WS resulted in 8–10% higher wet yield of liquid fraction and 17–20% of oil increase in liquid fraction than the control treatment. It is also notable that temperature positively impacted oil partitioning from WS. The results showed that ethanol could improve oil recovery from DDGS and oil partition in WS by varying different process conditions. This outcome is beneficial to ethanol plants to increase corn oil yield using their existing setup and in-situ product.

Quantification and Degradation of 2,2-Dibromo-3-Nitrilopropionamide (DBNPA) in Bioethanol Fermentation Coproducts

2,2-Dibromo-3-Nitrilopropionamide (DBNPA) has been used as a biocide in industrial water applications due to its instantaneous antimicrobial activity and rapid chemical breakdown. In this study DBNPA is considered as a potential alternative for antibiotics used for bacterial control during corn to ethanol fermentation. A method using LC/MS/MS was developed to accurately quantify DBNPA in water. When this method was applied to quantify DBNPA concentration in a fermentation matrix, DBNPA was found to be unstable and to decay rapidly, preventing validation of the method or quantitation. This method was then used to evaluate the degradation rate of DBNPA in whole stillage, which is the nonvolatile residue produced by removal of ethanol from corn-based fermentation beer by distillation through the relative decrease in measured signal. In addition, a method was developed and validated to quantify bromide, one of the degradation products of DBNPA, in whole stillage using LC/MS/MS. The degradation rate of DBNPA in whole stillage was found to display first order kinetics with a calculated half-life of 85 min. Laboratory analytical chemistry results on DBNPA degradation were confirmed in field trials.

Toward an Understanding of Physical and Biological Properties of Corn-Based Whole Stillage, Thin Stillage, and Condensed Distillers Solubles and Changes Thereof During Storage

The production of bio-based ethanol has been one of the fastest growing industries in the United States during the past decade. Thus, wider exploration of ethanol coproduct uses is necessary in the ethanol plant. Currently, process steams such as whole stillage, thin stillage, and syrup are processed into distiller dried grains with solubles and fed to livestock. The storability of whole stillage, thin stillage, and syrup influences the economic and energetic balances of fuel ethanol production. However, there are few investigations of the shelf life for these products or how to measure these quantities. The objectives of this research were to test physical and biological properties of whole stillage, thin stillage, and syrup and determine storability and allowable shelf life for these materials as influenced by storage temperature levels. Using standard laboratory methods, several properties were determined, including moisture content, water activity, thermal properties (conductivity, resistivity, volumetric heat capacity, and diffusivity), color, mold development, and CO2 production. Also, the separation processes due to settling were observed over 72 h. The thin stillage and whole stillage had relative high average moisture contents of 92% (w.b.) and 87% (w.b.), respectively, and a mean water activity of 0.99; the high water content marked samples easily susceptible to rapid spoilage. Time had a significant effect (p < 0.05) on properties of coproducts. Both thin stillage and whole stillage samples got mold growth after 5 days incubation at 32°C. Thin stillage had the greatest separation rate in the settling experiment. However, syrup had a relative low average moisture content of 62% and an average water activity of 0.92. No mold growth and settling separation happened in syrup samples. There was no evidence showing that a linear relationship exists between Hunter L*, a* and b*, and mold growth. The Solvita® test showed that high-temperature treatment caused high CO2 production in all samples. The exponential models described the relationship between storage time (from 0 to 5 days at 25 and 35°C) and CO2 concentration for the three coproducts. This study is a first step to explore opportunities for utilizing valuable components from these coproducts. Follow-up study should work on separation processes to concentrate the valuable components of these coproducts. Exploring the potential value of ethanol coproducts could maintain and improve the profitability of the ethanol industry.

122 Nutrient digestibility of heat pretreated or multienzyme treated corn whole stillage for pigs

A study was conducted to determine standardized ileal digestibility (SID) of amino acids (AA) and net energy value (NE) for pigs of heat-pretreated or enzyme-predigested corn whole stillage (WS; slurry material that is dried into DDGS). Ten ileal-cannulated barrows (initial BW = 65.6 ± 3.5 kg) were fed 5 diets in a replicated 5 × 5 Latin square design. The diets were cornstarch-based, containing corn DDGS, untreated WS (C-WS), heat-pretreated WS (Heat-WS) or enzyme-predigested WS (Predigested-WS), and N-free diet. Digestibility of AA in feedstuffs was determined by the direct method. Energy digestibility in feedstuffs was determined by difference from the N-free diet. The WS was heat pretreated at 140 °C and 70 psi for 15 min. Predigestion of the WS was achieved by incubating with multienzyme that supplied xylanase, celullase, α-galactosidase at 2.4, 2.0 and 2.3 mg per gram of WS, respectively, for 12 h at 55 °C. On DM basis, DDGS, C-WS, Heat-WS, Predigested-WS contained 32.8, 30.8, 28.18, and 39.7% CP, 39.8, 51.0, 52.2 and 53.8% NDF, and 4.5, 4.6, 5.7 and 4.5% EE, respectively. The SID of Lys for C-WS (75.5%) was greater (P < 0.05) than that for C-DDGS (67.4%) and Heat-WS (53.9%), but lower (P < 0.05) than for Predigested-WS (84.1%). The NE value for C-WS (2,793 kcal/kg) did not differ from that of C-DDGS (2,668 kcal/kg DM). The NE value for C-WS was greater (P < 0.05) than that for Heat-WS (1,834 kcal/kg DM) and lower than that for Predigested-WS (2,814 kcal/kg DM). In conclusion, enzymatic predigestion of WS increased its SID of Lys and NE value, and hence it can be an attractive technology to increase the nutritive value of corn DDGS for pigs. Heat pretreatment reduced SID of AA and NE values of the WS.

127 Porcine in vitro digestibility of whole stillage predigested with multi-enzyme during different time periods

A study was conducted to determine the effects of the period of predigesting whole stillage (WS; slurry material that is dried into DDGS) with multi-enzyme and composition of the multi-enzyme on porcine in vitro digestibility of dry matter (IVDDM) of the WS. Four samples of whole stillage from 4 different sources were freeze-dried and divided into 13 subsamples to give 52 sub-samples. Thirteen treatments were applied to the 48 sub-samples within source. The treatments were undigested WS (control); or pre-digested with 1 of 3 multi-enzymes (MTE1, MTE2, and MTE3) at 55 °C for 6, 12, 18 or 24 h in 3 × 4 factorial arrangement. The MTE1 contained xylanase, β-glucanase, cellulase, mannanase, protease, and amylase; MTE2 contained xylanase, α-galactosidase, and cellulase; and MTE3 contained xylanase, cellulase, β-glucanase, and mannanase. The 52 subsamples were subjected to porcine in vitro digestion. The IVDDM of untreated WS was 73.3%. The IVDDM increased (P< 0.05) with an increase in the predigestion period. However, a rise in the predigestion period from 0 to 12 h resulted in greater (P< 0.05) response in mean IVDDM than an increment in the predigestion period from 12 to 24 h (11 vs. 0.83 percentage points). Predigestion period and multi-enzyme type interacted on IVDDM such that the improvement in IVDDM between 0 and 12 hours of predigestion differed (P< 0.05) among the 3 multi-enzyme types (13.3, 11.1, and 8.5 percentage points for MTE3, MTE2, and MTE1, respectively). The LS means by multi-enzyme treatment were modeled and resulted in unparallel curves (P< 0.05). The estimated maximum response of IVDDM for MTE1, MTE2 and MTE 3 were 82.4%, 84.7% and 87.1% at 15.8, 13 and 13.1 hours, respectively. In conclusion, the optimal time of predigestion of WS with multi-enzymes (with regard to improvement in its IVDDM) was approximately 14 h.

126 Porcine in vitro digestion and fermentation characteristics of heat and multi-enzyme pretreated whole stillage

Effects of heat pretreatment (HT) and multi-enzyme predigestion (MP) of whole stillage on porcine in vitro digestibility of DM (IVDDM) and fermentation characteristics of WS were investigated. Four WS samples were obtained from 4 different sources. Half amount of WS from each source was pretreated at 70psi and 160°C for 20 min. Untreated and pretreated WS samples from each source were divided into 4 sub-samples (4 sub-samples of untreated WS per source and 4 sub-samples of pretreated WS per source) to give 32 sub-samples. Four treatments were applied to 32 sub-samples WS (1 untreated or 1 pretreated sub-sample per treatment per sample source). The treatments were WS undigested or pre-digested with 1 of 3 multi-enzymes (MTE1, MTE2, and MTE3). The MTE1 contained xylanase, β-glucanase, cellulase, mannanase, protease, and amylase; MTE2 contained xylanase, α-galactosidase, and celullase; and MTE3 contained xylanase, cellulase, β-glucanase, and mannanase. The 32 sub-samples were subjected to porcine in vitro digestion in 3 cycles of 2 batches (16 sub-samples/batch). Subsequently, residues were subjected to porcine in vitro fermentation for 72 hours, during which accumulated gas production was recorded and modeled to estimate kinetics of gas production. The IVDDM of untreated WS was 73.4%. HT improved (P< 0.05) of WS IVDMM by 8.2 percentage points. MP improved IVDDM of untreated WS and heat-pretreated WS by a means 9.1 and 6.8 percentage points, respectively. However, the magnitude of improvement in IVDDM of pretreated WS due to predigestion was lower (P< 0.05) for MTE3 than that for MTE2 (4.8 vs. 9.0 percentage points), but similar to that for MTE1 (6.7 percentage points). Similar interactions were observed for total gas production. In conclusion, the digestibility of WS was improved by the HT and MP. Combination of HT and MTE2 predigestion was the most effective in improving digestibility of WS.

361 Porcine in vitro degradation and fermentation characteristics of heat pretreated corn whole stillage

Pre-treatment of whole stillage (WS; slurry material that is dried into DDGS) with heat can improve digestibility of the resulting DDGS by pigs. A study was conducted to identify optimal conditions (time and temperature) for heat pre-treatment of corn WS. Six samples of WS from different sources were divided into 13 sub-samples to give a total of 78 sub-samples. Thirteen treatments were applied to 13 sub-samples from each source (1 sub-sample/treatment). The treatments were untreated WS, and WS that was pre-treated (70 psi) for 10, 20, or 30 minutes and at 100, 120, 140, or 160 °C in a 3 × 4 factorial arrangement. Sub-samples were subjected to in vitro digestion with porcine pepsin and pancreatin, followed by in vitro fermentation for 72 h. Accumulated gas production was recorded and modeled to estimate kinetics of gas production. Volatile fatty acids (VFA) concentration in fermented solutions was also measured. Pre-treatment time and temperature did not interact on in vitro digestibility of DM (IVDDM), and total gas and VFA production. Pre-treatment time did not affect total gas and VFA production. The IVDDM for untreated WS was 73.4%. An increase in pre-treatment temperature from 100 to 160 °C resulted in linear and quadratic increase in IVDDM by 11%. Response surface analysis indicated that maximum IVDDM resulted from relatively long pre-treatment times (20–30 mins) and highest pre-treatment temperature. An increase in pre-treatment temperature from 100 to 160 °C resulted in linear increase in total gas production by 13%; maximum total gas production resulted from relatively short pre-treatment times (10–20 mins) and highest pre-treatment temperature. Total VFA production was unaffected by pre-treatment time. In conclusion, in vitro digestibility and fermentability of WS was improved by heat pre-treatment. Optimal conditions for pre-treatment of WS for combined improved digestibility and fermentability were 160 °C and 20 mins.

Co-Culture of Filamentous Feed-Grade Fungi and Microalgae as an Alternative to Increase Feeding Value of Ethanol Coproducts

Distiller’s grains, an important commodity in the feed and food chains, are currently underdosed in rations due to several factors, mainly nutrient imbalance. This study aimed to increase the linoleic acid content in distiller’s grains and decrease the excess nutrients in stillage water by the use of an artificial lichen, composed of fungi, algae, and a supporting matrix. A maximum concentration of 46.25% of linoleic acid in distiller’s grains was achieved with a combination of Mucor indicus and Chlorella vulgaris using corn-to-ethanol whole stillage as substrate. Microbial hydrolytic enzymes during fermentation were able to decrease the solids in whole stillage. Nitrogen depletion by microalgal uptake causes lipid-formation stress to Mucor indicus cells, increasing linoleic acid production to about 49% of the total lipids, potentially decreasing costs in the animal feed. The culture supernatant can potentially be recycled as process water to the ethanol fermentation tank, and enhanced distiller’s grains can replace animal-specific diets. This would reduce exogenous enzyme use and supplementation of unsaturated fatty acids from other sources.