Michael J. Kurantz

Dry-grind process for fuel ethanol by continuous fermentation and stripping.

Conversion of a high‐solids saccharified corn mash to ethanol by continuous fermentation and stripping was successfully demonstrated in a pilot plant consuming 25 kg of corn per day. A mathematical model based on previous pilot plant results accurately predicts the specific growth rate obtained from these latest results. This model was incorporated into a simulation of a complete dry‐grind corn‐to‐ethanol plant, and the cost of ethanol production was compared with that of a conventional process. The results indicate a savings of

Production of eicosapentaenoic acid by the filamentous fungus Pythium irregulare

0.03 per gallon of ethanol produced by the stripping process. The savings with stripping result from the capacity to ferment a more concentrated corn mash so there is less water to remove downstream.

Effect of cultural conditions on production of eicosapentaenoic acid by Pythium irregulare

Because of the diversity of their lipids and fatty acid biosynthetic pathways, lower fungi may find utilization as sources of omega-3 or other polyunsaturated fatty acids (PUFA). Production of eicosapentaenoic acid (EPA) by the filamentous fungus, Pythium irregulare, has been demonstrated in 14-1 fermentors. Sweet whey permeate (lactose) was preferred over glucose as a substrate for production of a high-EPA-content lipid. Characterization of the lipid indicated that approximately 90% of the EPA was contained in the neutral lipid fraction. A specific productivity of 24.9 mg EPA/g dry biomass was achieved at 14°C, at which temperature the lipid contained 25.5% EPA and 54.2% PUFA. This is the highest mycelial EPA content for a fungal lipid that has been reported in the literature.

Water vapor permeability and solubility of zein/starch hydrophilic films prepared from dry milled corn extract

SummaryThe effect of culture conditions upon lipid content and fatty acid composition of mycelia ofPythium irregulare was investigated with particular attention to increasing the yield of 5,8,11,14,17-eicosapentaenoic acid (20∶5; ω−3) (EPA). All experiments were done by shake flask culture using a yeast extract + malt extract medium. The maximum growth rate was obtained at 25°C, but maximum EPA production was obtained at 12°C. The highest EPA production was 76.5 μg EPA/ml 13 days fermentation at 12°C. Addition of glucose during fermentation increased the yield considerably. The highest yield was 112 μg/ml, obtained at 13 days fermentation with spiking on day 11. Fermentation time could be shortened by initial incubation at 25°C for 2 days, followed by incubation at 12°C for 6 days. The culture also produced arachidonic acid and other ω-6 polyunsaturated fatty acids. EPA production was also obtained with lactose or sweet whey permeate, a by-product of cheese manufacture that contains lactose as the main carbohydrate.

Hydrocyclone separation of dry-milled corn

Abstract Zein films containing different levels of starch were prepared from extracts of dry milled com which had been previously rinsed in a hydrocyclone to improve the extractability of the zein as well as film formation. Zein was isolated from the rinsed dry milled corn by extraction with 70% (v/v) ethanol. Comparison of RP-HPLC profiles indicated the presence of β- and γ-zeins in the extracted isolate which were not found in commercial zein. Water vapor barrier properties of the glycerine-plasticized films prepared from extracted zein isolates, containing approximately 8% starch, were comparable to films prepared from commercial zein. Water resistance of zein isolate films decreased with increasing starch content.

Kinetics of continuous fermentation and stripping of ethanol

ABSTRACT Corn milled to 590 μm were soaked for 1 hr in solutions with a range of glucose concentration providing liquid specific gravities above and below that of the lighter fraction (corn germ). A suspension of these particles was pumped through a hydrocyclone to separate the germ particles and to rinse watersoluble compounds from the corn. The specific gravity of the hydrocyclone streams (suspensions), as well as liquid phase (after solids settling) was measured, and product compositions and particle sizes were determined. This work shows that a germ-enriched fraction of corn ground to <1 mm, can be separated with a hydrocyclone. To enable computer simulation of the corn-treatment process, the experimental data was used to construct a two-component model of the hydrocyclone separation of the milled corn. In the model, the milled and sieved corn is virtually separated into germ and endosperm streams that are fed to paired hydrocyclone models. Hydro...

Ethanolic extraction of zein from maize

A pilot plant consisting of a 30-liter fermenter, and a 10-cm packed column with a blower and condenser to recover ethanol vapors was operated continuously for 185 days. On-line washing of the packing in the column twice weekly with condensed ethanol from the process (approximately 45% v/v) controlled fouling by attached yeast cells. Steady-state glucose consumption rates of up to 800 gh-1, condensed ethanol production rates of up to 26 l/day, and consistently high ethanol yield of approximately 0.50 gg-1 glucose were observed. Data from the pilot plant showed that the primary inhibitory effect of ethanol on the steady-state fermenter performance was to decrease the cell yield, while the specific glucose consumption rate was almost unaffected by ethanol concentrations up to 65 gl-1. A new kinetic model is introduced to represent these effects.

Effects of ethanol concentration and stripping temperature on continuous fermentation rate

Abstract Zein can be extracted from maize (Zea mays) using ethanol solutions, and recovered from the extract by diluting with water. Dilution to 40% ethanol will precipitate a mixture of zein and maize lipid with ∼15% lipid. For possible zein applications, such as film production, purer zein is required. Most of the lipid can be removed from the precipitate by selective re-extraction with hexane or ethanol, but this is expensive. A precipitate containing 90% or more of the protein in the extract, with less than 10% lipid, can be obtained by diluting the extract in stages. An initial dilution will precipitate a solid with 75% or more lipid, this precipitate can be centrifuged from the extract and the centrifugate diluted to precipitate a solid of 70% or more zein. The mass and composition of solid centrifuged from a maize extract that was diluted in several steps to characterize the composition of precipitates so formed. The lipid content of a zein product precipitated from an extract diluted from 55% ethanol to 50% is significantly lower than the content of precipitate of an extract diluted in a single step to 40% ethanol.

Preparative chromatography of oligogalacturonic acids

Abstract The operation of a pilot plant consisting of a 14-l fermentor, 10-cm packed column and condenser for continuous fermentation and stripping of ethanol was stable for more than 100 days. The feed consisted of a non-sterile solution of 560 g/l glucose with 100 g/l corn steep water. Fouling of the packing in the column with attached growth of yeast cells was controlled by in situ washing at intervals of 3–6 days. A computer simulation of the pilot plant was developed and used to analyze the data. The productivity of the continuous fermentor varied from 14 g ethanol to 17 g ethanol l−1 h−1. The yield was equal to the maximum theoretically possible: 0.51 g ethanol/g glucose consumed. Results are fit to linear models for the effects of ethanol concentration on specific growth rate and cell yield, and for the effect of stripping temperature on specific growth rate.

Control of packed column fouling in the continuous fermentation and stripping of ethanol

Abstract A mixture of oligogalacturonic acids was prepared by partial enzymatic hydrolysis of citrus pectin-derived α- d -polygalacturonic acid. Both a commercial fungal “pectinase” preparation and a purified endo-polygalacturonase isolated from this source by chromatography on carboxymethyl Sephadex C-50 were used to catalyze the hydrolysis. Different product distributions resulted, but even when using pectinase there was no evidence for the formation of unsaturated products from activity of polygalacturonic acid lyase. Individual oligogalacturonic acids were isolated by step-gradient elution (sodium formate, pH 4.7) from the macroporous strong base anion-exchange resin AG MP-1 in the formate form. Pure oligomers to heptagalacturonic acid were isolated in a single run, including gram quantities of tri-, tetra-, and pentagalacturonic acid. The individual oligogalacturonic acids were characterized by fast-atom bombardment mass spectrometry in positive and negative modes.