Light Steep Water Research Articles

Phosphorus fractionation and protein content control chemical phosphorus removal from corn biorefinery streams.

The economic viability of corn biorefineries depends heavily on the sale of coproducts as animal feeds, but elevated phosphorus (P) contents can exacerbate manure management issues. Phosphorus removal from light steep water and thin stillage, two concentrated in-process aqueous streams at wet milling and dry-grind corn biorefineries, could simultaneously generate concentrated fertilizer and low-P animal feeds, but little is known regarding how differences in stream composition affect removal. To address this data gap, we show that the solubility of P in light steep filtrate (LSF) and thin stillage filtrate (TSF) exhibits distinct sensitivity to calcium (Ca) and base addition due to differences in P fractionation and protein abundance. In LSF, P was primarily organic, and near-complete removal of P (96%) was observed at pH 8 and a Ca/total P (TP) ratio of 2. In TSF, TP removal was lower (81%), and there was more equal distribution of organic and orthophosphate, indicating that the Ca requirements of inorganic P precipitation were a limiting factor. The C/H/N ratio, elemental characterization, and crude protein analysis of the precipitated solids indicated that coprecipitation of amorphous solids containing Ca, Mg, and K with soluble proteins facilitated removal of P, particularly in LSF. Although the removal mechanisms and solubility limits differed, these results highlighted the magnitude (40-70mM) and efficacy (80-96%) of P recovery from two biorefinery streams.

Techno‐economic feasibility of phosphorus recovery as a coproduct from corn wet milling plants

AbstractBackground and objectivesWet milling (WM) plants contribute to both point source and nonpoint source phosphorus (P) pollution by concentrating P in the coproduct corn gluten feed (CGF), the majority of which is undigested when consumed by ruminants, leading to manure management concerns. Phosphorus runoff from the manure consequently causes eutrophication in the water bodies downstream. This study investigates the economic feasibility of recovering the phosphorus at the front end from light steepwater to reduce P in CGF.FindingsThe amount of phosphorus in CGF was observed to reduce from 11.94 mg/g (db) to 2.44 mg/g (db), with phosphorus removal in the recovery unit calibrated with laboratory experiments. Direct fixed capital cost of $6.9 MM was estimated for the phosphorus recovery unit in an existing WM plant.ConclusionsWith a phosphorus recovery rate of 0.17 MT/hr, the operating cost of P recovery at the front end was estimated to be $1.23/kg‐P removed.Significance and noveltyRamifications of excess phosphorus in CGF on environment are an important understudied area. This study provided economic and technical feasibility of phosphorus recovery from CGF in WM industry, consequently producing a new coproduct and reducing the environmental burden.

Distribution Analysis of Twelve Mycotoxins in Corn and Corn-Derived Products by LC-MS/MS to Evaluate the Carry-Over Ratio during Wet-Milling.

This study investigated the distribution of twelve mycotoxins (aflatoxins B1, B2, G1, and G2; ochratoxin A; fumonisins B1 and B2; deoxynivalenol; nivalenol; zearalenone; T-2 toxin; and HT-2 toxin) in corn and corn by-products (corn bran, cornstarch, corn gluten, corn gluten feed, corn germ, light steep water, and corn steep liquor) produced by wet-milling in Korea. Fifty-two samples were collected from three factories producing cornstarch and other corn by-products. The samples were pretreated on an immunoaffinity column (IAC), and then the levels of the 12 mycotoxins were analyzed simultaneously by liquid chromatography-coupled triple-quadrupole mass spectrometry (LC-MS/MS). Fusarium mycotoxins were mainly found in raw corn and corn gluten feed samples. Other mycotoxins—such as aflatoxins, ochratoxin A, and HT-2 toxin—were detected in tiny amounts below the limit of quantification (LOQ) in cornstarch, corn germ, and corn bran. Ochratoxin A and nivalenol were mainly carried over into cornstarch. Aflatoxin B1, deoxynivalenol, T-2 toxin, HT-2 toxin, and the fumonisins were concentrated in corn gluten feed. Zearalenone was evenly distributed in all corn by-products except cornstarch during the milling process.

옥수수 침지액의 효모발효를 통한 고효율 피틴 생산공정 개발

A simple method for improving the phytin production process by yeast fermentation of light steep water (LSW) of corn was developed in this study. The initial acidity of LSW was pH 4 because it contained 3% (w/v) lactic acid, and the pH increased to 7.5 after 33 h of yeast fermentation to produce phytin at a final concentration of 1.0% (w/v) without addition of Ca(OH)2. The phytin produced by yeast fermentation showed 12.3% (w/w) protein content, which corresponds to 28.9% of that obtained by neutralization of LSW. The settling rate of phytin produced by the yeast fermentation was 1.6 times faster than that with the neutralization method.

An integrated approach to the degradation of phytates in the corn wet milling process

An integrated process was developed to hydrolyze the phytates in light steep water (LSW) and to simultaneously isolate inorganic phosphate (Pi) and myo-inositol products. The proposed integrated process will be helpful in resolving the environmental and nutritional concerns in the use of corn gluten feed (CGF) in the animal diets. This process comprised of partial and total hydrolysis of LSW and intermediate anion exchange separation technique. The phytates in LSW were initially degraded to negatively charged myo-inositol phosphates (InsP(2)-InsP(5)). The optimized experimental parameters for the partial hydrolysis of LSW were determined to be 2 h hydrolysis with 1FTU Aspergillus niger/g substrate at 35 degrees C. The negatively charged species of the partially hydrolyzed substrate were separated on a strong base anion exchange resin. The negatively charged species, retained by the resin, were eluded with 1M NaCl solution and were subjected to complete hydrolysis with the Escherichia coli, A. niger derived phytases and their respective combinations. The maximum amount of myo-inositol released from the anion exchange column was 3.73+/-0.03 mg/NaCl elution which was detected after 48 h reactions catalyzed by 100 FTU E. coli, 150 FTU E. coli, and 150 FTU the combination of A. niger and E. coli. The time course of Pi released showed a similar trend to that of myo-inositol and the released Pi reached a maximum amount of 3.30+/-0.05 mg/g NaCl elution after 48 h incubation at the enzyme loadings for which the maximum concentration of myo-inositol were reached.

Degradation of Phytates in Distillers’ Grains and Corn Gluten Feed by Aspergillus niger Phytase

Distillers' dried grains with solubles (DDGS) and corn gluten feed (CGF) are major coproducts of ethanol production from corn dry grind and wet milling facilities, respectively. These coproducts contain important nutrients and high levels of phytates. The phytates in these products cannot be digested by nonruminant animals; consequently, large quantities of phytate phosphorus (P) are deposited into the soil with the animal wastes which potentially could cause P pollution in soil and underground water resources. To reduce phytates in DDGS and CGF, a phytase from Aspergillus niger, PhyA, was investigated regarding its capability to catalyze the hydrolysis of phytates in light steep water (LSW) and whole stillage (WS). LSW and WS streams are the intermediate streams in the production of CGF and DDGS, respectively, and contribute to most of the P in these streams. Enzyme loadings with activity of 0.1, 1, 2, and 4 FTU/g substrate and temperatures of 35 and 45 degrees C were investigated regarding their influences on the degree of hydrolysis. The analysis of the hydrolyzate suggested to a sequentially degradation of phytates to lower order myo-inositol phosphate isomers. Approximately 90% phytate P of LSW and 66% phytate P of WS were released, suggesting myo-inositol monophosphate as the end product. The maximum amount of released P was 4.52 +/- 0.03 mg/g LSW and 0.86 +/- 0.01 mg/g WS.

Distribution of phosphorus compounds in corn processing

Distillers dried grains with solubles (DDGS) and corn gluten feed (CGF) are major coproducts of ethanol production from corn dry grind and wet milling facilities, respectively. These coproducts contain important nutrients, nevertheless, high levels of phosphorus (P). About 50–80% of the P in these products is in an organically bound form known as phytate. The phytate P in these products cannot be digested by nonruminant animals. Consequently, large quantities of phytate are deposited into the soil with the animal wastes which potentially could cause P pollution in soil and underground water resources. As regulations on the concentration of P material in ethanol production coproducts become more restrictive, measures need to be taken for effective extraction of phytate P from the coproducts to make these processes more environmentally compatible. Proper marketing of coproducts is critical to the overall economy of ethanol production facilities. In this study, distribution of P compounds in different streams of dry grind and wet milling operations was determined. In the dry grind process, the highest P concentration was found to be in the condensed distillers solubles (CDS) at about 1.34 wt.% (db). About 59% of P in this stream was in phosphates form. The highest concentration of P in the wet milling process was found in the light steep water at about 3.4 wt.% (db). In this stream, about 22% of P was attributed to phosphates.

Phosphorus Concentrations and Flow in Maize Wet‐Milling Streams

ABSTRACTMarketing of coproducts such as corn gluten meal (CGM) and corn gluten feed (CGF) is important to the maize wet‐milling industry. High phosphorus concentrations could lead to limited markets for CGF due to its potential to increase phosphorus in animal wastes. The objective was to measure the concentration and flow of phosphorus in the wet‐milling process and identify streams that could be altered. Samples were taken from 21 process streams of three facilities and the phosphorus content of each was determined. Flow of phosphorus was simulated using a computer model for a 2,700 tonne/day (105,000 bu/day) wet‐milling plant. Phosphorus concentrations of streams varied from <10 mg/kg to >14,000 mg/kg. Phosphorus content of many streams differed significantly among facilities. Flow of phosphorus (kg/day) varied dramatically among streams. However light steepwater, light gluten, and process water streams (5,960, 3,080, and 970 kg/day, respectively) accounted for much of the phosphorus flow. Modification of these streams could reduce phosphorus content of coproducts. The high phosphorus content of either CGF or CGM could be reduced markedly if phosphorus was reduced in the appropriate streams.

Characterization of light gluten and light steep water from a corn wet milling plant

The primary commodity of corn wet milling is starch, but two coproducts (corn gluten feed, CGF and corn gluten meal, CGM) also are produced. CGM and CGF are marketed as animal foodstuffs and are important economically; however, variation in composition reduces quality. There are few data on the effect of composition of the parent process streams, light steep water (LSW) and light gluten (LG), respectively, on composition of CGF and CGM. The objective was to characterize LG and LSW. Samples of LG and LSW were collected: (1) hourly for one day, (2) every 3 h for 3 days, and (3) daily for 3 weeks. Dry matter, N and ash were determined. Variation in composition of LG and LSW was greatest during longer periods of time (days and weeks) rather than shorter (hourly or every 3 h). There was significant variation in DM (solids) content, which directly affected the concentration of other components. Variation in N (protein) of LG and LSW accounted for much of the variation in CGF and CG. Processes that modify processing and reduce variation could increase the quality of CGF and CGM.

Technique to Measure Surface‐Fouling Tendencies of Steepwater from Corn Wet Milling

ABSTRACTSurface‐fouling tendencies of raw light steepwater (LSW) and membrane‐filtered light steepwater (FSW) from corn wet‐milling were studied using an annular fouling probe. The probe contained a heated surface to simulate the surface temperature of an evaporator. The heated region caused a fraction of solids in the steepwater to adhere to the surface, thus fouling the probe over time. FSW samples were prepared by filtering LSW using a microfiltration membrane with a nominal pore size of 0.1 μm. Fouling tendencies of both samples were established at an initial probe wall temperature of 99°C. Batches (30 L) were circulated through the fouling probe until the inner surface temperature of the probe reached 200°C. Temperature and power supplied to the probe were measured over time and used to calculate fouling resistance and rate of fouling. Measurement of maximum fouling resistance and fouling rate had a coefficient of variation (COV) of 5.1 and 7.4%, respectively. Maximum fouling resistances attained over a 12‐hr period were 0.36 and 0.049 m2 °C/kW for LSW and FSW, respectively. Average rates of fouling were 4.53 × 10‐4 and 0.82 × 10‐4 m2 °C/kW/min for LSW and FSW, respectively, showing an 80% decrease in fouling rate using microfiltration to remove 19% of solids.

A LABORATORY-SCALE CONTINUOUS COUNTERCURRENT STEEP SYSTEM FOR CORNWET-MILLING— PART II. EVALUATION OF SYSTEM STABILITY

The purpose of this work was to evaluate the stability of a countercurrent steep system to ensure that variables, including temperature, pump flow rate and steepwater profiles remain stable during long periods of operation. Four runs of a laboratory-scale continuous countercurrent steep system were used to evaluate its thermal and mechanical stability. One run was started with fresh steepwater while the other three were inoculated with light steepwater obtained from a wetmilling plant. Variables, such as steep temperature, steepwater recycle rate and light steepwater draw rate, were monitored. Steepwater characteristics, including pH, SO2 concentration, lactic acid concentration and steepwater solids content were determined. Six to eight days were required for all of the steepwater variables (pH, SO2 and lactic acid concentration and steepwater solids content) to reach steady state when light steepwater from a plant was used to inoculate the system. When fresh steepwater was used, 12 d were needed. The average steep temperature of the 16 tanks during 16 d of continuous operation was 50 ± 1°C with a setpoint of 50 ± 2°C. The average pump flow rate for the 8 pumps was 5.0 ± 0.1 mL/s when the setpoint was 5.0 mL/s. The average light steepwater draw rate over nine days was 593 ± 49 mL/kg when the setpoint was 600 mL/kg. Corn steeped in this system was wet-milled and product yields were reproducible.

Production of ethanol from starch by co-immobilizedZymomonas mobilis-glucoamylase in a fluidized-bed reactor

The production of ethanol from starch was studied in a fluidized-bed reactor (FBR) using co-immobilized Zymomonas mobilis and glucoamylase. The FBR was a glass column of 2.54 cm in diameter and 120 cm in length. The Z. mobilis and glucoamylase were co-immobilized within small uniform beads (1.2-2.5 mm diameter) of kappa-carrageenan. The substrate for ethanol production was a soluble starch. Light steep water was used as the complex nutrient source. The experiments were performed at 35 degrees C and pH range of 4.0-5.5. The substrate concentrations ranged from 40 to 185 g/L, and the feed rates from 10 to 37 mL/min. Under relaxed sterility conditions, the FBR was successfully operated for a period of 22 d, during which no contamination or structural failure of the biocatalyst beads was observed. Volumetric productivity as high as 38 g ethanol/(Lh), which was 74% of the maximum expected value, was obtained. Typical ethanol volumetric productivity was in the range of 15-20 g/(Lh). The average yield was 0.49 g ethanol/g substrate consumed, which was 90% of the theoretical yield. Very low levels of glucose were observed in the reactor, indicating that starch hydrolysis was the rate-limiting step.

Production of succinic acid by anaerobiospirillum succiniciproducens

The effect of an external supply of carbon dioxide and pH on the production of succinic acid by Anaerobiospirillum succiniciproducens was studied. In a rich medium containing yeast extract and peptone, when the external carbon dioxide supply was provided by a 1.5M Na2CO3 solution that also was used to maintain the pH at 6.0, no additional carbon dioxide supply was needed. In fact, sparging CO2 gas into the fermenter at 0.025 L/L-min or higher rates resulted in significant decreases in both production rate and yield of succinate. Under the same conditions, the production of the main by-product acetate was not affected by sparging CO2 gas into the fermenter. The optimum pH (pH 6.0) for the production of succinic acid was found to be in agreement with results previously reported in the literature. Succinic acid production also was studied in an industrial-type inexpensive medium in which light steep water was the only source of organic nutrients. At pH 6.0 and with a CO2 gas sparge rate of 0.08 L/L-min, succinate concentration reached a maximum of 32 g/L in 27 h with a yield of 0.99 g succinate/g glucose consumed.

5593855 Method of using yeast to recover phytin by precipitation from cornsteep liquor or light steep water : Lee Youl-Lark; Park Sang-Jae Seoul, Republic of Korea Assigned to Doosan Technical Center

5593855 Method of using yeast to recover phytin by precipitation from cornsteep liquor or light steep water : Lee Youl-Lark; Park Sang-Jae Seoul, Republic of Korea Assigned to Doosan Technical Center

Five Years of Experience with the Application of Reverse Osmosis on Light Middlings in a Corn Wet Milling Plant

AbstractCorn wet milling is a water intensive operation. A modern corn wet milling plant typically uses 1,5 m3 of fresh water per t of corn. Much of this added water must subsequently be removed by processes that are energy intensive to varying degrees. A major breakthrough in reducing the water consumption of the corn wet milling process was made when A. Cicuttini perceived the idea of using reverse osmosis more upstream in the corn wet milling process, to recover pure water from light middlings, the overflow from the hydrocyclone starch washing system, and to re‐use this water for starch washing. In doing so the direct relation between the amount of water used for washing the starch, and the amount of light steep water to be evaporated does no longer exist. A full size reverse osmosis system for this service has been installed in one of the CPC corn wet milling plants in 1982. In a first phase a reduction of the load to the steepwater evaporator of 50% has been obtained. Expansion of the reverse osmosis system enabled further reduction of the steepwater evaporator load down to 30% of the original value. The system has demonstrated its ability to operate in conjunction with a 9‐stage starch washing section with a wet fresh water intake for starch washing, comparable to that of a 15‐stage washing section, at the same high level of starch product quality, and at much lower energy cost. The disappearance of the direct link between fresh water consumption for starch washing and steep water evaporator load creates new possibilities for optimisation and flexibility in design and operation of corn wet milling plants.