Method for treatment of corn hulls

Corn hulls and like materials are subjected to a treatment to obtain two fractions therefrom comprising a holocellulose fraction and a non-carbohydrate fraction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the treatment of corn hulls and similar 
materials. More particularly, this invention relates to the treatment of 
corn hulls and similar materials to obtain two fractions therefrom 
comprising a holocellulose fraction and a non-carbohydrate fraction. 
2. Description of the Prior Art 
Many processes are known in the art for obtaining various fractions from 
plant materials. For example, wood chips may be treated to obtain 
cellulose having varying degrees of purity. Typically, wood pulping 
processes involve treatments at high temperatures under highly alkaline or 
acid conditions and may include the use of certain chlorine and sulfur 
compounds to assist in the solubilization of lignin. The liquor resulting 
from such treatments may comprise mixtures of lignins, hemicellulose, 
various sugars and degradation products. Efforts have been made to recover 
various components of the liquor but such have not proven entirely 
satisfactory due, principally, to the large amounts of degradation 
products present. 
One approach which has been taken to minimize the formation of degradation 
products is the utilization of alcohols for removal of lignins in the 
pulping process. U.S. Pat. Nos. 1,856,567 to Kleinert et al. and 2,037,001 
to Aronovsky disclose various procedures for the alcoholic extraction of 
wood pulp. U.S. Pat. No. 2,166,540 to Bailey teaches the treatment of 
lignified cellulosic material with an aqueous alkaline solution of 
alcohol. Pulping using aqueous ethanol at high temperatures is described 
by T. N. Kleinert in Tappi, Vol. 57, No. 8, August 1974. 
There are a number of procedures disclosed in the art directed to the 
extraction of hemicellulose from fibrous waste products such as corn 
hulls, cotton seed hulls, oat hulls and the like utilizing aqueous alkali. 
Exemplary of such procedures are those disclosed in U.S. Pat. Nos. 
1,819,233 to Darling; 2,218,567 to White; 2,709,699 to Wolf et al.; 
2,801,955 to Rutenberg et al.; 2,868,778 to Watson et al.; and 3,879,373 
to Gerrish et al. These procedures generally suffer the disadvantage of 
producing a colored, impure, hemicellulose product. German 
Offenlegungsschrift Nos. 2,358,472 and 2,365,457 disclose processes for 
treating oat hulls to recover xylose, cellulose and lignin. 
U.S. Pat. No. 3,716,526 to Schweiger teaches a method for producing a 
relatively pure hemicellulose product whereby corn hulls are first 
subjected to an alkaline extraction procedure to produce a crude 
hemicellulose product and then treating such product with an aqueous 
organic-acid containing liquid to solubilize the impurities. 
OBJECTS OF THE INVENTION 
It is the principal object of the present invention to provide a process 
for treating corn hulls and similar materials to obtain two fractions 
therefrom. 
It is a further object of the present invention to provide a process for 
treating corn hulls and similar materials to obtain two fractions 
therefrom, one composed of substantial quantities of cellulose and 
hemicellulose and the other characterized as a non-carbohydrate fraction. 
These and other objects will be apparent from the following specification 
and claims. 
SUMMARY OF THE INVENTION 
Corn hulls and similar materials are subjected to an alkaline hydrolysis 
treatment under conditions whereby a non-carbohydrate fraction is 
solubilized and the resulting residue comprises a holocellulose fraction. 
DETAILED DESCRIPTION OF THE INVENTION 
The teachings and disclosures of U.S. Pat. No. 4,038,481 entitled "Method 
for Treatment of Corn Hulls"-Antrim et al. are incorporated herein by 
reference. 
In U.S. Pat. No. 4,038,481, a process is disclosed whereby three fractions 
are obtained from corn hulls and similar materials. By contrast, the 
present invention is directed to obtaining two fractions from corn hulls 
and similar materials. One fraction is composed of substantial quantities 
of cellulose and hemicellulose and is hereinafter referred to as the 
holocellulose fraction. The other fraction is non-carbohydrate in 
character. 
The holocellulose fraction has utility as a bodying agent for various 
products, e.g., food products, and can also be treated to obtain certain 
sugars, such as arabinose and the like. 
Two approaches may be utilized in the present process. Common to both 
approaches is that in the first step, an alkaline hydrolysis treatment is 
utilized. In the first approach, the hydrolysis is performed using an 
alkaline water-miscible organic solvent system. Sufficient water should be 
present to solubilize the alkali and the non-carbohydrate fraction, but 
insufficient to solubilize appreciable quantities of the hemicellulose. 
The amount of water which may be tolerated is dependent upon a number of 
factors such as the particular solvent utilized, temperature of treatment 
and the like. In the case when the solvent is ethanol, substantial 
quantities of hemicellulose will be solubilized if the amount of water 
exceeds about 40 percent. In general, however, the extraction solution 
will comprise from about 60 to about 90 percent solvent and the remainder 
water. This extraction solution will contain the non-carbohydrate 
fraction. The residue from the extraction treatment will comprise the 
holocellulose fraction. 
In the second approach, the alkaline hydrolysis treatment is carried out 
under conditions whereby minimal water, for instance, an amount not 
exceeding about 65 percent based on the weight of the corn hulls and 
preferably from about 25 to about 55 percent on the same weight basis, is 
utilized so that the hemicellulose fraction does not migrate from the corn 
hull structure. Next, the treated corn hulls are contacted with a 
water-miscible organic solvent to extract the non-carbohydrate fraction. 
The residue from the extraction treatment will comprise the holocellulose 
fraction. 
A variety of water-miscible organic solvents may be utilized in the present 
process. Exemplary of such are acetone, methanol, ethanol, propanol, 
isopropanol, secondary butyl alcohol, tertiary butyl alcohol, and mixtures 
thereof. 
The amount of holocellulose recovered is, of course, dependent upon the 
conditions under which the alkaline hydrolysis is carried out and, while 
the cellulose portion thereof is relatively inert in regard to 
solubilization, the hemicellulose is not and can be relatively easily 
solubilized if caution is not taken to prevent such from occurring. 
The major proportion of the non-carbohydrate fraction may be recovered by 
solvent extraction under a variety of conditions, although it is preferred 
that the extraction be performed at least once with an aqueous organic 
solvent system having a pH below about 4 and more preferably a pH of from 
about 2 to about 3. This will ensure substantially complete removal of the 
non-carbohydrate fraction. 
The amount of holocellulose obtained in the present process may vary over a 
range of from about 55 to below about 95 percent, but preferably the 
holocellulose will be from about 65 to about 80 percent. 
The non-carbohydrate fraction contains relatively large quantities of 
ferulic acid. In the case when the non-carbohydrate fraction obtained is 
above about 15 percent, such fraction contains above about 10 percent 
ferulic acid. When the non-carbohydrate fraction obtained is from about 20 
to about 25 percent, the ferulic acid content of the extracted 
non-carbohydrate fraction is from about 10 to about 20 percent, on the 
same weight basis. 
In order to more clearly describe the nature of the present invention, a 
specific example will hereinafter be described. It should be understood, 
however, that this is done solely by way of example and is not intended to 
delineate the scope of the invention or limit the ambit of the appended 
claims. 
Percentages referred to herein are based upon the weight of the corn hulls 
or like material unless otherwise specified.

EXAMPLE I 
This Example illustrates the separation of corn hulls into holocellulose 
and non-carbohydrate fractions. 
Corn hulls from a corn wet milling operation were placed on a U.S. #6 
screen and sprayed with sufficient water at a temperature of 50.degree. C 
to remove the fine fiber, most of the starch and some proteinaceous and 
lipid material. The corn hulls retained on the screen were slurried in 
water at a solids concentration of 10 percent, the pH was adjusted with 
lime to approximately 6.5, and sufficient amount of alpha-amylase (Novo 
Termamyl-60) was added to the slurry to obtain therein a dosage of about 
three liquefons/g of hull solids. The hulls were filtered, washed and 
dried. 
Into a 250 ml 3-neck flask equipped with stirrer, heater and condenser was 
placed 14.18 g dry basis of corn hulls and 150 ml of 63.3 percent (v/v) 
aqueous isopropanol containing 1.5 g of sodium hydroxide. The reaction 
mixture was stirred and heated at reflux for four hours then cooled and 
filtered through a medium porosity sintered glass funnel. The insoluble 
residue was suspended in 150 ml of 63.3 percent (v/v) aqueous isopropanol, 
the pH was adjusted to 3.0 using dilute hydrochloric acid and the 
suspension was stirred approximately one hour at room temperature. The 
mixture was filtered through a sintered glass funnel and the extraction 
process was again repeated using 150 ml of 63.3 percent (v/v) aqueous 
isopropanol. All filtrates were combined, the pH was adjusted to 3.0 using 
dilute hydrochloric acid and the volume was adjusted to one liter with 
isopropanol. Twenty ml of this solution was taken to dryness at 
approximately 25.degree. C using a rotary evaporator and reduced pressure. 
The dry sample was then analyzed for ferulic acid content by gas-liquid 
chromatography. 
The holocellulose residue was first air dried and then dried in a vacuum 
oven at 105.degree. C. 
The ferulic acid content of the non-carbohydrate fraction was 17.7 percent 
which represented a yield of 3.43 percent dry basis based on the starting 
corn hulls. 
Yields obtained were 80.3% holocellulose and 19.4% non-carbohydrate 
fraction, based on dry basis corn hulls. 
Analysis of Corn Hull Holocellulose 
Dry Substance -- 99.19% 
% Ash, d.b. -- 1.05 
% Protein (N x 6.25), d.b. -- 0.49 
% Fat (Hexane), d.b. -- 0.32 
% Lignin, d.b. -- 0.05 
The terms and expressions which have been employed are used as terms of 
description and not of limitation, and it is not intended in the use of 
such terms and expressions to exclude any equivalents of the features 
shown and described or portions thereof, since it is recognized that 
various modifications are possible within the scope of the invention 
claimed.