Membrane separation of solids from corn processing streams

Corn processing streams are characterized by high water content. Removal of water and recovery of solids are major economic and logistical challenges. New technologies are needed to modify processing streams and to reduce variability and improve quality of coproducts. The objective was to determine the effectiveness of microfiltration and ultrafiltration systems in altering water, solids (protein) and ash contents of corn processing streams. Corn was either steeped with SO(2) (STW) or soaked (SKW) in water; STW contained more solids than SKW. Ultrafiltration of STW and SKW had little effect on water removal or solids recovery. Corn was processed by a conventional wet milling process and a wet milling process that used enzymes to eliminate use of SO(2) steeping. Protein streams from the conventional process (CG) and the enzymatic process (EG) were processed by microfiltration. Permeate streams from EG and CG had higher total solids and ash concentrations than retentate streams; much of the ash was recovered in permeate (67% and 83%, respectively). For CG, proteins were largely recovered in retentate, whereas for EG, proteins were recovered in permeate. SDS-PAGE data indicated a decrease in size of proteins in the EG process stream. Permeate streams from microfiltration were subject to ultrafiltration; there was little effect on solids and nutrient separations.     

Characterization of gluten processing streams

Corn gluten meal (CGM) is a major coproduct of corn wet milling; it has value because of high protein. However, variation in composition and high P content reduce market value. Data that characterize gluten streams would be helpful in identifying key processing steps that could be modified to improve the quality of CGM and increase processing efficiency. Few data are published in the literature on the detailed composition of gluten processing streams. The objective was to characterize the gluten process streams in a corn wet milling plant.Samples were obtained from one plant over a six month period and analyzed for dry matter (DM), total N (protein), ash and elements. DM and macroelement content of the streams were increased significantly during processing. Ash, priority pollutant elements and microelement concentrations were low and of little concern. About 38% of the N (protein) in light gluten was not recovered in the CGM; most of this was lost at the gluten thickener step into the gluten thickener overflow. Much of the P also was removed at this step. Modification of the gluten thickener overflow to increase N and reduce P could make CGM a more valuable coproduct and improve processing efficiency.     

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.     

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.     

Murine leukemia virus clearance by flocculation and microfiltration

Clearance of murine leukemia virus from CHO cell suspensions by flocculation and microfiltration was investigated. Murine leukemia virus is a retrovirus that is recommended by the U.S. Food and Drug Administration for validating clearance of retrovirus-like particles. Due to biosafety considerations, an amphotropic murine leukemia virus vector (A-MLV) that is incapable of self-replication was used. Further, A-MLV is incapable of infecting CHO cells, thus ensuring that infection of the CHO cells in the feed did not result in a reduced virus titer in the permeate. The virus vector contains the gene for the enhanced green fluorescent protein (EGFP) to facilitate assaying for infectious virus particles. The virus particles are 80-130 nm in size. The feed streams were flocculated using a cationic polyelectrolyte. Microfiltration was conducted using 0.1 and 0.65 microm pore size hollow fiber membranes. The level of virus clearance in the permeate was determined. For the 0.1 microm pore size membranes a 1,000-fold reduction in the virus titer in the permeate was observed for feed streams consisting of A-MLV, A-MLV plus flocculant, A-MLV plus CHO cells, and A-MLV plus flocculant and CHO cells. While the flocculant had little effect on the level of virus clearance in the permeate for 0.1 microm pore size membranes, it did lead to higher permeate fluxes for the CHO cell feed streams. Virus clearance experiments conducted with 0.65 microm pore size membranes indicate little clearance of A-MLV from the permeate in the absence of flocculant. However, in the presence of flocculant the level of virus clearance in the permeate was similar to that observed for 0.1 microm pore size membranes. The results obtained here indicate that significant clearance of A-MLV is possible during tangential flow microfiltration. Addition of a flocculant is essential if the membrane pore size is greater than the diameter of the virus particles. Flocculation of the feed stream leads to an increase in the permeate flux.     

Purification during crossflow electromicrofiltration of fermentation broth

The present study was to investigate the purification of a fermentation broth by an electromicrofiltration membrane. Microfiltration runs with a crude and a centrifuged broth, with solution of particles recovered from centrifugation and with permeates from microfiltration experiments were thus compared.Microfiltration performances were governed by colloids and small particles that induced sharp initial flux declines. For these results, the evolution of the overall membrane resistance was increased by 80% in comparison with the electromicrofiltration membrane. The main focus of this study was set on the enhancement of the filtrate flux by an electric field. This pressure electrofiltration leads to a drastic improvement of the filtration by 100% and the filtration time was thereby reduced. Pressure electrofiltration serves as an interesting alternative to the cross-flow filtration and it effectively separates advantageous constituents such as amino acids and biopolymers from a fermentation broth. They were equally maintained during the microelectrofiltration, although they were significantly reduced by 45% by the microfiltration without the application of an electric field. Accordingly, since the electrofiltration membrane was provided more permeability, this study experimentally demonstrates that the permeability inside a membrane can be controlled using an electric field.     

Fractionation of transgenic corn seed by dry and wet milling to recover recombinant collagen‐related proteins

Corn continues to be considered an attractive transgenic host for producing recombinant therapeutic and industrial proteins because of its potential for producing recombinant proteins at large volume and low cost as coproducts of corn seed‐based biorefining. Efforts to reduce production costs have been primarily devoted to increasing accumulation level, optimizing protein extraction conditions, and simplifying the purification. In the present work, we evaluated two grain fractionation methods, dry milling and wet milling, to enrich two recombinant collagen‐related proteins; thereby, reducing the amount and type of corn‐derived impurities in subsequent protein extraction and purification steps. The two proteins were a full‐length human recombinant collagen type I alpha 1(rCIα1) chain with telopeptides and peptide foldon to effect triple helix formation and a 44‐kDa rCIα1 fragment. For each, ～60% of the rCIα1s in the seed was recovered in the dry‐milled germ‐rich fractions making up ca. 25% of the total kernel mass. For wet milling, ～60% of each was recovered in three fractions accounting for 20–25% of the total kernel mass. The rCIα1s in the dry‐milled germ‐rich fractions were enriched three to six times compared with the whole corn kernel, whereas the rCIα1s were enriched 4–10 times in selected wet‐milled fractions. The recovered starch from wet milling was almost free of rCIα1. Therefore, it was possible to generate rCIα1‐enriched fractions by both dry and wet milling along with rCIα1‐free starch using wet milling. Because of its simplicity, the dry milling procedure could be accomplished on‐farm thus minimizing the risk of inadvertent release of viable transgenic seeds. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Enhanced virus removal by flocculation and microfiltration

In this work we have investigated the feasibility of virus clearance by flocculation and tangential flow microfiltration. Chinese hamster ovary cell feed streams were spiked with minute virus of mice and then flocculated using cationic polyelectrolytes prior to tangential flow microfiltration. Our results indicate that flocculation prior to microfiltration leads to more than 100 fold clearance of minute virus of mice particles in the permeate. Today, validation of virus clearance is a major concern in the manufacture of biopharmaceutical products. Frequently new unit operations are added simply to validate virus clearance thus increasing the manufacturing cost. The results obtained here suggest that virus clearance can be obtained during tangential flow microfiltration. Since tangential flow microfiltration is frequently used for bioreactor harvesting this could be a low cost method to validate virus clearance.     

The study of metabolite-separation using an electromicrofiltration appratus

This study was performed to investigate the recovery of dissolved metabolic constituents produced during fermentation, using an electromicrofiltration apparatus. Filtration experiments were performed with crude and with permeate from electromicrofiltration and microfiltration. The results of each method were compared with a focus on measuring the enhancement of the filtrate flux with the application of an electric field. Hydraulic electrofiltration was found to significantly improve filtration and serves as an interesting alternative to cross-flow filtration for the separation of advantagenous constituents, such as amino acids and biopolymers from the fermentation broth.     

An approach for the identification of exemplar sites for scaling up targeted field observations of benthic biogeochemistry in heterogeneous environments

Headwater streams influence the biogeochemical characteristics of large rivers and play important roles in regional and global carbon budgets. The combined effects of seasonality and land use change on the biogeochemistry of headwater streams, however, are not well understood. In this study we assessed the influence of catchment land use and seasonality on the composition of dissolved organic matter (DOM) and ecosystem metabolism in headwater streams of a Kenyan river. Fifty sites in 34 streams draining a gradient of catchment land use from 100% natural forest to 100% agriculture were sampled to determine temporal and spatial variation in DOM composition. Gross primary production (GPP) and ecosystem respiration (ER) were determined in 10 streams draining primarily forest or agricultural catchments. Absorbance and fluorescence spectrophotometry of DOM reflected notable shifts in composition along the land use gradient and with season. During the dry season, forest streams contained higher molecular weight and terrestrially derived DOM, whereas agricultural streams were dominated by autochthonous production and low molecular weight DOM. During the rainy season, aromaticity and high molecular weight DOM increased in agricultural streams, coinciding with seasonal erosion of soils and inputs of organic matter from farmlands. Most of the streams were heterotrophic. However, GPP and ER were generally greater in agricultural streams, driven by higher dissolved nutrient (mainly TDN) concentrations, light availability (open canopy) and temperature compared with forest streams. There were correlations between freshly and autochthonously produced DOM, GPP and ER during both the dry and wet seasons. This is one of the few studies to link land-use with organic carbon dynamics and DOM composition. Measures of ecosystem metabolism in these streams help to affirm the role of tropical streams and rivers as important components of the global carbon cycle and demonstrate that even semi-intensive, smallholder agriculture can have measurable effects on riverine ecosystem functioning.     

Accelerating sample preparation through enzyme‐assisted microfiltration of Salmonella in chicken extract

Microfiltration of chicken extracts has the potential to significantly decrease the time required to detect Salmonella, as long as the extract can be efficiently filtered and the pathogenic microorganisms kept in a viable state during this process. We present conditions that enable microfiltration by adding endopeptidase from Bacillus amyloliquefaciens to chicken extracts or chicken rinse, prior to microfiltration with fluid flow on both retentate and permeate sides of 0.2 μm cutoff polysulfone and polyethersulfone hollow fiber membranes. After treatment with this protease, the distribution of micron, submicron, and nanometer particles in chicken extracts changes so that the size of the remaining particles corresponds to 0.4–1 μm. Together with alteration of dissolved proteins, this change helps to explain how membrane fouling might be minimized because the potential foulants are significantly smaller or larger than the membrane pore size. At the same time, we found that the presence of protein protects Salmonella from protease action, thus maintaining cell viability. Concentration and recovery of 1–10 CFU Salmonella/mL from 400 mL chicken rinse is possible in less than 4 h, with the microfiltration step requiring less than 25 min at fluxes of 0.028–0.32 mL/cm²  min. The entire procedure—from sample processing to detection by polymerase chain reaction—is completed in 8 h. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1551–1562, 2015     

Effects of recent increases in salinity and nutrient concentrations on the microbialite community of Lake Clifton (Western Australia): are the thrombolites at risk?

There has been a strong research focus on optical properties in temperate estuaries but very much less in tropical estuaries. These properties comprise light and beam attenuation dominated by suspended particulate matter, Chl a, and CDOM. Spatially and temporally distributed data on optical properties in a tropical wet and dry estuary are compared and discussed in relation to those of temperate estuaries. Sampling in the Nha Phu estuary, Vietnam, consisted of five stations on a transect from head to mouth that was sampled four times during dry conditions and three times during wet conditions between May 2006 and April 2008. Methods comprised CTD, optical measurements, and water sampling for suspended matter, Chl a, and CDOM. Results showed high light attenuation—K _d(PAR)—in wet conditions and low in dry. K _d(PAR) was highest at the estuary head and lower in the outer part. Spatial and temporal variations in K _d(PAR) were in general dominated by variations in suspended particulate matter concentrations in both wet and dry conditions. Chl a concentrations were low and showed no strong variations between wet and dry conditions. CDOM absorption coefficients were higher in wet conditions with high values at the head and lower in the central part of the estuary. The depth of the photic zone was reduced by up to 50% during wet conditions. A residence time in the estuary of 5–6 days was derived from the rate of change of K _d(PAR) after a period of heavy rain and discharge of freshwater into the estuary. This complied with a residence time of four and a half days derived from a basic physical relation. Optical properties were in general comparable to temperate estuaries in dry conditions although Chl a concentrations were lower in Nha Phu. A second distinctive point, as compared to temperate estuaries, was the episodic character with days of strong rainfall followed by longer periods of dry weather. All sampling, both wet and dry, was carried out in the dry season which implies a less definitive perception of wet and dry seasons.     

Background-free Detection of Mouse Antibodies on Mouse Tissue by Anti-isotype Secondary Antibodies

Immunodetection on mouse routinely processed tissue via antibodies raised in mice faces cross-reactivity of the secondary anti-mouse reagents with endogenous immunoglobulins, which permeate the tissue. Various solutions to this problem have been devised and include endogenous Ig block with anti-mouse Fab fragments or directly conjugated primary antibodies. Mouse isotype-specific antibodies, differently from reagents directed against both heavy and light chains, fail to detect endogenous Ig after fixation and embedding, while providing a clean and specific detection system for mouse antibodies on mouse routinely processed tissue.     

Dry ash,a better reference base than dry matter for heavy metals and other persistent pollutants

Concentrations of pollutants in biotic materials are usually related to dry matter. This work demonstrates with the use of heavy metal-contaminated poplar leaves (Populus nigra ‘Italica’), that ash of dry matter (dry ash) obviously yields a better reference, as it eliminates the natural variations among organic substance contents. Values of heavy-metal concentrations in dry ash of leaves were generally more homogeneous and better correlated with corresponding values in air and soil than those in dry matter. It is further shown that concentrations of non-biodecomposable and non-volatile pollutants in the mineral fraction (the same as ash) of, for instance, plants and their residues (autumn leaves, mulch compost) can directly be compared with those in soil (nearly 100% mineral), and vice versa. This facilitates the setting of maximally permissible values for pollutant concentrations in plant dry matter or their residues, and in soil, which can be used in the protection of soils against pollutants accumulated in fresh or fallen leaves, mulch or compost. In this connection, the heavy-metal and lindane margins in West German regulations for issuing environmental certificates for compost products are discussed.     

A wheat biorefining strategy based on solid-state fermentation for fermentative production of succinic acid

In this study, a novel generic feedstock production strategy based on solid-state fermentation (SSF) has been developed and applied to the fermentative production of succinic acid. Wheat was fractionated into bran, gluten and gluten-free flour by milling and gluten extraction processes. The bran, which would normally be a waste product of the wheat milling industry, was used to produce glucoamylase and protease enzymes via SSF using Aspergillus awamori and Aspergillus oryzae, respectively. The resulting solutions were separately utilised for the hydrolysis of gluten-free flour and gluten to generate a glucose-rich stream of over 140gl(-1) glucose and a nitrogen-rich stream of more than 3.5gl(-1) free amino nitrogen. A microbial feedstock consisting of these two streams contained all the essential nutrients required for succinic acid fermentations using Actinobacillus succinogenes. In a fermentation using only the combined hydrolysate streams, around 22gl(-1) succinic acid was produced. The addition of MgCO(3) into the wheat-derived medium improved the succinic acid production further to more than 64gl(-1). These results demonstrate the SSF-based strategy is a successful approach for the production of a generic feedstock from wheat, and that this feedstock can be efficiently utilised for succinic acid production.     

Ecoregion and land‐use influence invertebrate and detritus transport from headwater streams

Summary 1. Habitats are often connected by fluxes of energy and nutrients across their boundaries. For example, headwater streams are linked to surrounding riparian vegetation through invertebrate and leaf litter inputs, and there is evidence that consumers in downstream habitats are subsidised by resources flowing from headwater systems. However, the strength of these linkages and the manner in which potential headwater subsidies vary along climatic and disturbance gradients are unknown. 2. We quantified the downstream transport of invertebrates, organic matter and inorganic sediment from 60 fishless headwater streams in the Wenatchee River Basin located on the eastern slope of the Cascade Range in Washington, U.S.A. Streams were classified into four groups (each n = 15) based on their position within two ecological subregions (wet and dry) and the extent of past timber harvest and road development (logged and unlogged). 3. Time and ecoregion were significant for all response variables as transport varied across sampling periods, and dry ecoregion streams displayed significantly higher mean values. Logged sites also generally showed higher mean transport, but only inorganic sediment transport was significantly higher in logged sites. Both ecoregion and land‐use interacted significantly with time depending on the response variable. Differences among stream categories were driven by relatively low levels of transport in unlogged drainages of the wet ecoregion. Interestingly, unlogged dry ecoregion streams showed comparable transport rates to logged sites in the wet ecoregion. Dominance by deciduous riparian vegetation in all but unlogged streams in the wet ecoregion is a primary hypothesised mechanism determining transport dynamics in our study streams. 4. Understanding the quantity and variation of headwater subsidies across climate and disturbance gradients is needed to appreciate the significance of ecological linkages between headwaters and associated downstream habitats. This will enable the accurate assessment of resource management impacts on stream ecosystems. Predicting the consequences of natural and anthropogenic disturbances on headwater stream transport rates will require knowledge of how both local and regional factors influence these potential subsidies. Our results suggest that resources transported from headwater streams reflect both the meso‐scale land‐use surrounding these areas and the constraints imposed by the ecoregion in which they are embedded.     

Effectiveness of Biosorption-Assisted Microfiltration Process for Treatment of Domestic Wastewater

The efficiency of a biosorbent prepared from Eichhornia crassipes roots (ECR) was explored for the treatment of domestic sewage water in combination with low-cost ceramic microfiltration membrane. Batch sorption studies were conducted as a function of biosorbent dose, initial chemical oxygen demand (COD) loading, and temperature. Sorption equilibrium data of varying initial COD values (116–800 mg/L) indicated high potential of ECR for COD removal. Using 0.25 g/L of biosorbent dose, the equilibrium adsorption capacity was obtained as 2480 mg/g at 20°C for an initial COD loading of 800 mg/L. Microfiltration study was performed using ceramic membrane made from composition of α-alumina and clay. The effect of operating parameters on filtration characteristics was observed in terms of permeate flux. Permeate samples were characterized in terms of various parameters both for the direct filtration, as well as biosorbent-assisted filtration. The filtration behavior of wastewater at varying transmembrane pressure was explained using various membrane fouling models. The results suggested that microfiltration of domestic wastewater with incorporation of biosorbent (0.25 g/L) was highly effective for removal of organic load (>90%), turbidity (>99%), and total suspended solids (TSS) (93–95%) and the treated water quality was suitable for reuse in various purposes, such as gardening, floor and car washing, etc.     

Biomass and Total Lipid Content Assessment of Microalgal Cultures Using Near and Short Wave Infrared Spectroscopy

The technique of near and short wave near-infrared spectroscopy was assessed with respect to analysis of dry matter and lipid content of microalgae with potential for biodiesel production. Microalgal culture samples were filtered through GF/C filter papers and spectral measurements of wet and oven dried (60 °C overnight) filter papers over the ranges of 300–1,100 nm and 1,100–2,500 nm were recorded. Partial least square models on culture biomass and lipid content for combined species data were poor in terms of RMSECV, R _CV and the ratio of RMSECV to SD. A single species model for C. vulgaris based on 1,100–2,500 nm spectra of dry filtrate supported a model with RMSECV, R _CV and SDR values of 0.32 g L^?1, 0.955 and 3.38 for biomass and 0.089 g L^?1, 0.874 and 2.06 with lipid, respectively. However, the dry filtrate models on biomass and lipid content performed poorly in the prediction of samples drawn from an independent series of C. vulgaris cultured under N-, P- and Fe-limited growth trial. Thus, while the near-infrared spectroscopy technique has potential for assessment of dry matter and lipid content of microalgal cultures using a dried filtrate sample, further work is required to examine the limits to model robustness.     

Clearance of minute virus of mice by flocculation and microfiltration

Clearance of minute virus of mice (MVM) from CHO cell suspensions by flocculation and microfiltration has been investigated. MVM is a parvovirus that is recommended by the U.S. Food and Drug Administration for validating clearance of parvoviruses. The feed streams were flocculated using a cationic polyelectrolyte. Virus clearance in excess of 10,000-fold was obtained in the bulk permeate for flocculated feeds streams. However, the level of clearance was only about 10- to 100-fold for unflocculated feed streams. The results suggest that virus clearance involves interactions between the MVM particles, the cationic polyelectrolyte, and the CHO cells present. Validating virus clearance is a major concern in the biotechnology industry. New unit operations are frequently added to the purification train simply to validate virus clearance. However, many of these unit operations are less effective at validating clearance of nonenveloped viruses. Validating clearance of parvoviruses is often particularly problematic as they are nonenveloped and the virus particles are small (18 to 24 nm), making physical removal difficult. The results obtained herein indicate that addition of the cationic polyelectrolyte not only results in significant clearance of MVM but also leads to an increase in permeate flux.