Method for processing aqueous fermentation broths

A method for processing aqueous fermentation broths in a bioreactor vessel, in which a foam inhibitor is added to the fermentation broth in the bioreactor vessel in order to prevent the accumulation and buildup of foam in the bioreactor vessel caused by oxygen sparging of the fermentation broth contained therein. The aqueous fermentation broth processed in the bioreactor vessel is conveyed as a feed solution to an ultrafiltration system including a membrane for concentrating the aqueous fermentation broth. The ultrafiltration system is typically located downstream of the bioreactor vessel. The improvement involves reducing the amount of fouling of the membrane in the ultrafiltration system by adding to the aqueous fermentation broth in the bioreactor vessel as the foam inhibitor, an antifoam which is an oil based liquid in the form of droplets, the droplets of the oil based liquid antifoam being dispersed, encased, entrapped, and imbedded, within solid particles of a water soluble encapsulating material.

BACKGROUND OF THE INVENTION 
This invention relates to an improved process for treating fermentation 
broths in which a solid particulate form of encapsulated antifoam is 
employed in a bioreactor vessel in order that fouling be reduced in 
ultrafiltration equipment employed downstream of the bioreactor vessel 
during concentration of the broth. 
Fermentation processing involves organisms such as bacteria, yeast, and 
fungus, in a culture medium of a broth including starch, glucose, oxygen, 
and various proteins. The aqueous broth is allowed to ferment for a number 
of days, and as the broth is fermenting, the broth is supplied with a 
constant amount of oxygen in order to increase the rate of aerobic 
conversion. As a result of such oxygen sparging, and because of the 
presence of surface active proteins, a substantial amount of foam is 
produced in the bioreactor vessel. It has therefore been conventional 
practice to add a foam inhibitor to the broth in order to reduce the 
accumulation of foam. Traditionally, such foam inhibitors have been in the 
form of emulsions including droplets of oil dispersed in water. Such 
emulsion type antifoam formulations have necessarily included surfactants, 
coagulants, and gelatinous thickeners, for the purpose of stabilizing 
these antifoam formulations. 
Following completion of the microbial activity in the bioreactor, it is 
necessary to process the fermentation broth by concentrating the broth in 
order to separate desired products from the impurities contained in the 
broth. This processing is typically conducted by passing the fermentation 
broth from the bioreactor to a filtration unit located downstream of the 
bioreactor. The filtration systems employed are ultrafiltration units 
employing membranes. In these separation units, there is generated a high 
pressure bulk flow of broth across hydrophobic membranes having pore sizes 
ranging from 0.01 to 1.0 micron. The broth passes through the membrane, 
while the impurities sought to be separated are retarded by the membrane. 
These impurities constitute, for example, cells, proteins, and bacteria. 
It has been found that such membranes are highly sensitive to fouling and 
clogging, with the result that the filtration rate, expressed as flux 
through the membrane, is inhibited; the product yield is reduced; and 
there is a corresponding reduction in the life-span of the membrane 
itself. One contributing factor to membrane fouling, clogging, and 
filtration rate inhibition, is believed to be the presence in the antifoam 
emulsion of the various surfactants, coagulants, and thickeners, used to 
stabilize emulsion type antifoams. These surfactants, coagulants, and 
thickeners, form a gel layer at the interface of the membrane and the 
aqueous phase, and the gel layer clings to the surface of the membrane, 
inhibiting the filtration rate of the effluent therethrough. 
Thus, it should be apparent that there exists a need for an antifoam 
formula-ion which will effectively inhibit the formation of foam in the 
fermentation broth in the bioreactor, and which will also allow high 
efficiency filtration rates through the membrane, and without the 
formation of flux inhibiting gel layers prone to foul the membrane and 
reduce its efficiency. 
Encapsulated antifoams are not new, nor is the encapsulation of antifoams 
in water soluble materials new or novel. For example, it has recently been 
reported that a new process for encapsulating liquids or solids in a 
cornstarch matrix for slow release has been developed by the USDA Northern 
Regional Research Center. The matrix consists of a compound produced from 
amylose and amylopectin. In order to encapsulate a herbicide, for example, 
cornstarch is cooked in a jet of steam to gelatinize the starch. The 
herbicide, insect lure, plant growth regulator, fertilizer, medicine, 
flavoring, coloring, or vitamin, is mixed in; dried; and the mixture may 
be crumbled or ground to granules or particles, respectively. In United 
Kingdom Published Unexamined Application No. 2180254, filed Sept. 10, 
1986, and published Mar. 25, 1987, a sugar such as sucrose is used in a 
detergent composition but acts, rather than an encapsulant, to increase 
the dispersibility of the detergent. In European Published Unexamined 
Application No. 0171457, filed Aug. 17, 1984, published Feb. 19, 1986, 
particles of sugar such as lactose are embedded in a semi-permeable 
membrane and then dissolved, releasing water soluble actives. 
In U.S. Pat. No. 3,159,585, issued Dec. 1, 1964, various oils such as 
vegetable fats are encapsulated with dextrins. Sugar in the form of 
mixtures of mannitol, sorbitol, and refined cane sugar, are used to 
encapsulate mineral oil in U.S. Pat. No. 3,779,942, issued Dec. 18, 1973. 
Fragrance oils, spice oils, perfume oils, and fruit flavors, are taught in 
U.S. Pat. No. 3,971,852, issued July 27, 1976, to be encapsulated in a 
mixture of dextrin and a sugar such as sucrose, fructose, and glucose. In 
U.S. Pat. No. 4,481,157, issued Nov. 6, 1984, a mixture of gelatin, 
sorbitol, water, and a coagulant, such as a liquid paraffin, is used to 
encapsulate vegetable oil. A bulk laxative containing methylcellulose 
particulates encapsulated in sucrose is disclosed in U.S. Pat. No. 
4,732,917, issued Mar. 22, 1988. 
A silicone antifoam formulation is disclosed in United Kingdom Patent No. 
892,787, granted Mar. 28, 1962, and in which an organosiloxane emulsion 
including fume silica, is spray dried along with methylcellulose in order 
to form encapsulated antifoam particles. Other encapsulating materials are 
disclosed to be starch, gelatin, albumen, gum acacia, locust bean gum, 
carrageena, polyvinyl alcohol, polyethylene glycol, and guar gum. 
However, all of the foregoing references require the presence of one or 
more of a surfactant, coagulant. thickener, or additive, in order to 
stabilize the system. In addition, none relate specifically to 
environments including ultrafiltration equipment or membrane separators, 
nor do the references relate to fluid treatment systems such as 
fermentation processes requiring such ultrafiltration equipment or 
membrane separators. 
There is described in PCT International Publication No. WO 86/05411, 
published Sept. 25, 1986, an ultrafiltration system that employs a 
silicone alkylene oxide copolymer as a foam inhibitor for the fluids 
processed therein. This antifoam material is allegedly does not 
permanently foul the membrane, in comparison to conventional antifoam 
formulations containing additives such as emulsifying agents. It is noted, 
however, that in the event the membrane does become fouled, that the 
fouling process can be reversed by cleaning the membrane using 
conventional techniques such as flushing the membrane with cold water or 
with a mild bleach solution. The silicone alkylene oxide copolymeric 
antifoam material of the PCT International Publication is also disclosed 
to be operable in functioning as a foam inhibitor in the absence of 
emulsifiers, solvents, and finely divided insoluble matter. 
In accordance with the present invention, a novel alternative foam 
inhibitor is provided, which foam inhibitor is effective for use, for 
example, in methods for processing aqueous fermentation broths in a 
bioreactor vessel, in which the broth is conveyed downstream as a feed 
solution to an ultrafiltration system including a membrane for 
concentrating the aqueous fermentation broth. The foam inhibitor is in the 
form of an oil based liquid in the form of droplets, the droplets of the 
oil based liquid antifoam being dispersed, encased, entrapped, and 
imbedded, within solid particles of a water soluble encapsulating 
material. The encapsulated particulate antifoam is free of additives known 
to inhibit the filtration rate through the membrane, such as surfactants, 
coagulants, and thickeners. When added to the fermentation broth, the 
bland encapsulating material of the present invention, dissolves and 
releases the additive free active antifoam ingredient into the aqueous 
phase in the bioreactor vessel. 
Unlike the silicone alkylene oxide copolymer of the PCT International 
Publication referred to previously, the antifoams of the present invention 
meet the requirements of and are permissible in most foods, as established 
under rulings of the United States Food and Drug Administration. Further, 
the materials of the present invention are in an otherwise solid 
particulate form, rendering them capable of a programmed form of release 
of the antifoam encapsulated therein, in contrast to the bulk fluids of 
the PCT International Publication. 
SUMMARY OF THE INVENTION 
This invention relates to a method for processing aqueous solutions in a 
treating vessel, in which a foam inhibitor is added to the treating vessel 
in order to prevent the accumulation and buildup of foam therein, and in 
which the aqueous solution processed in the treating vessel is conveyed as 
a feed solution to an ultrafiltration system including a membrane. The 
ultrafiltration system is typically located downstream of the treating 
vessel, but the system can also constitute part of the recirculation 
process in certain instances as well. The improvement involves employing 
as the foam inhibitor in the treating vessel, an antifoam which is an oil 
based liquid in the form of droplets. The droplets of the oil based liquid 
antifoam are dispersed, encased, entrapped, and imbedded, within solid 
particles of a water soluble encapsulating material. 
The invention is also directed to a method for processing aqueous 
fermentation broths in a bioreactor vessel, in which a foam inhibitor is 
added to the fermentation broth in the bioreactor vessel in order to 
prevent the accumulation and buildup of foam in the bioreactor vessel, 
caused by oxygen sparging of the fermentation broth contained therein. The 
aqueous fermentation broth processed in the bioreactor vessel is conveyed 
as a feed solution to an ultrafiltration system, including a membrane for 
concentrating the aqueous fermentation broth. The ultrafiltration system 
is typically located downstream of the bioreactor vessel. The improvement 
in this process involves reducing the amount of fouling of the membrane in 
the ultrafiltration system by adding to the aqueous fermentation broth in 
the bioreactor vessel as the foam inhibitor, an antifoam which is an oil 
based liquid in the form of droplets. The droplets of the oil based liquid 
antifoam are dispersed, encased, entrapped, and imbedded, within solid 
particles of a water soluble encapsulating material. 
In some particular and preferred embodiments of the present invention, the 
oil based liquid antifoam is selected from the group consisting of 
silicone oils, vegetable oils, and mineral oils. The water soluble 
encapsulating material is selected from the group consisting of sugars and 
hydrolysis products of starch, and can include such materials as 
maltodextrin, glucose, maltose, sucrose, fructose, xylose, and lactose. 
The antifoam should be otherwise free of surfactants, thickeners, and 
coagulants, or other additives which tend to clog the membrane. 
These and other features, objects, and advantages, of the present invention 
will become more apparent when considered in light of the following 
detailed description thereof.

DETAILED DESCRIPTION OF THE INVENTION 
Ultrafiltration is a separation technique in which a liquid including small 
dissolved molecules is forced through a porous membrane. Large dissolved 
molecules, colloids, and suspended solids which do not migrate through the 
membrane pores are retained. The membranes are typically constructed of 
polymeric materials such as cellulose acetates, polyamides, polysulfones, 
vinyl chloride-acrylonitrile copolymers, and polyvinylidene fluoride. The 
membrane may be employed in the form of a flat sheet; a parallel leaf 
cartridge including several flat plates each with a membrane on both 
sides; a plate and frame assembly; a spirally wound cartridge of a pair of 
membrane sheets separated by a flexible porous support; supported tubes; 
and pleated sheets. Such ultrafiltration equipment is adapted to a wide 
variety of processing applications including, for example, protein 
recovery; the manufacture of cheese and yogurt; the concentration of oil 
and water emulsions; lanolin recovery; the concentration and purification 
of enzymes; antibiotic manufacture; alcohol fermentation., sewage 
treatment; and blood fractionation and purification. One distinct 
disadvantage of ultrafiltration is that retained materials which do not 
pass through the pores of the membrane tend to collect on the surface of 
the membrane, forming a gel layer which limits the filtration rate 
expressed as flux. In order to minimize the thickness of the gel layer, 
such systems are designed so that the flow of influent sweeps across the 
membrane surface. Material is recirculated in order to maintain a 
sufficient velocity across the surface of the membrane. 
Often ultrafiltration units are used in processes wherein the 
ultrafiltration equipment is deployed at a location downstream of a 
treatment type vessel. These vessels frequently require the addition of 
foam inhibiting agents during the treatment process. While such foam 
inhibiting agents are effective in preventing the buildup of foam in the 
treatment vessel; the surfactants, coagulants, and thickeners, used to 
stabilize such antifoam agents, are one of the major contributors in the 
maintenance of the gel layer. 
In an effort to minimize the contribution of materials to the gel layer 
formed at the surface of the membrane, the antifoam formulation of the 
present invention excludes surfactants, coagulants, and thickeners, or 
other additives, typically found in foam inhibiting agents. Exemplary of 
materials sought to be excluded from the compositions of the present 
invention are common surfactants such as glycerol monostearate, 
polyoxyethylene sorbitan tristearate, and polyoxyethylene monostearate; 
and thickeners such as xanthan gums, hydroxypropyl methylcellulose, and 
carboxy methylcellulose. This exclusion of additive materials is 
accomplished by encapsulating the antifoam active ingredient in a water 
soluble material in the form of a solid particulate. In this solid 
particulate encapsulated form, the antifoam active ingredient is otherwise 
preserved in a stabilized fashion, and can be stored for extended periods 
of time prior to being used. Upon addition of the particles of 
encapsulated antifoam to an aqueous system, the water soluble material is 
dissolved, releasing the antifoam active ingredient into the aqueous phase 
in order to perform its foam inhibiting function. 
The water soluble material used to encapsulate the antifoam active 
ingredient in accordance with the present invention, can be either a 
hydrolysis product of starch such as maltodextrin, or a sugar such as 
glucose, maltose, sucrose, fructose, xylose, and lactose. Maltodextrin is 
the preferred encapsulating material because of its bland characteristics. 
The antifoam active may contain a finely divided particulate filler, 
typically, silica, in addition to the fluid component of the antifoam. The 
fluid component of the antifoam active ingredient may be one or more of, 
or mixtures of, oil based liquids such as mineral oils and vegetable oils. 
Preferred vegetable oils are soybean oil, peanut oil, corn oil, rapeseed 
oil, coconut oil, palm oil, olive oil, sesame oil, cottonseed oil, 
sunflower oil, and safflower oil. There may also be used, in addition to 
mineral oils and vegetable oils, an oil based liquid of a silicone. 
The term silicone denotes a polymer of the formula 
##STR1## 
wherein n is an integer between zero and three, and m is two or more. The 
simplest silicone materials are the polydimethylsiloxanes. 
Polydimethylsiloxanes have the structure 
##STR2## 
where x is an integer of from one to about one hundred thousand. The 
repeating unit of the polymer 
##STR3## 
is the dimethylsiloxane unit. The terminal unit (Me3SiO) is the 
trimethylsiloxy group. At low molecular weights, silicones are fluids, and 
at high molecular weights, they are gums which may be cross-linked to form 
elastomeric products. The methyl group in a silicone may be substituted by 
a variety of other substituents including for example, phenyl, vinyl, and 
hydrogen. Conventional silicones are the trimethylsiloxy terminated 
polydimethylsiloxanes. Such materials are available in viscosities ranging 
from 0.65 to 2,500,000 centistokes. Substituents on the silicon consist of 
methyl groups or oxygen. Termination of the polymer chain prevents 
viscosity change and other alterations of the physical properties of the 
silicone polymeric materials. The polydimethylsiloxanes exhibit 
characteristic properties of low viscosity change with temperature; 
thermal stability; oxidative stability; chemical inertness; 
non-flammability; low surface tension; high compressibility; shear 
stability; and dielectric stability. In resin forming polysiloxanes, some 
of the methyl groups are hydrolyzable and permit the formation of Si-O-Si 
cross-links upon heating in the presence of a catalyst, but in the 
organosilicon fluids and oils, substantially all of the methyl groups are 
non-hydrolyzable and the fluid is heat stable. 
The polydimethylsiloxane fluid used herein as the antifoam agent is a high 
molecular weight polymer having a molecular weight in the range from about 
200 to about 200,000, and has a viscosity in the range from about 20 to 
2,000,000 centistokes, preferably from about 500 to 50,000 centistokes, 
more preferably about 550 to 1,200 centistokes at 25.degree. C. The 
siloxane polymer is generally end-blocked either with trimethylsilyl or 
hydroxyl groups but other end-blocking groups are also suitable. The 
polymer can be prepared by various techniques such as the hydrolysis and 
subsequent condensation of dimethyldihalosilanes, or by the cracking and 
subsequent condensation of dimethylcyclosiloxanes. 
The polydimethylsiloxane fluid antifoam agent can be present in combination 
with particulate silica. Such combinations of silicone and silica can be 
prepared by affixing the silicone to the surface of silica, for example, 
by means of the catalytic reaction disclosed in U.S. Pat. No. 3,235,509. 
Foam regulating agents comprising mixtures of silicone and silica Prepared 
in this manner preferably comprise silicone and silica in a 
silicone:silica ratio of from 20:1 to 200:1, preferably about 25:1 to 
about 100:1. The silica can be chemically and/or physically bound to the 
silicone in an amount which is preferably about 0.5% to 5% by weight, 
based on the silicone. The particle size of the silica employed in such 
silica/silicone foam regulating agents is finely divided and should 
preferably be not more than 100 microns, preferably from 2 microns to 20 
microns. 
Alternatively, silicone and silica can be prepared for use in the antifoam 
agent by admixing a silicone fluid of the type herein disclosed with a 
hydrophobic silica having a particle size and surface area in the range 
disclosed above. Any of several known methods may be used for making a 
hydrophobic silica which can be employed herein in combination with a 
silicone as the foam regulating agent. For example, a fumed silica can be 
reacted with a trialkyl chlorosilane (i.e., "silanated") to affix 
hydrophobic trialkylsilane groups on the surface of the silica. In a 
preferred and well known process, fumed silica is contacted with 
trimethylchlorosilane. A preferred material comprises a hydrophobic 
silanated, most preferably trimethylsilanated, silica, intimately admixed 
with a dimethyl silicone fluid having a molecular weight in the range of 
from about 200 to about 200,000, at a weight ratio of silicone to 
silanated silica of from about 20:1 to about 200:1, preferably from about 
20:1 to about 100:1. 
Yet another type of material suitable herein as the polydimethylsiloxane 
fluid antifoam comprises polydimethylsiloxane fluid, a silicone resin and 
silica. The silicone "resins" used in such compositions can be any 
alkylated silicone resins, but are usually those prepared from 
methylsilanes. Silicone resins are commonly described as 
"three-dimensional" polymers arising from the hydrolysis of alkyl 
trichlorosilanes, whereas the silicone fluids are "two-dimensional" 
polymers prepared from the hydrolysis of dichlorosilanes. The silica 
components of such compositions are microporous materials such as fumed 
silica aerogels and xerogels having particle sizes and surface areas 
herein-above disclosed. 
The mixed polydimethylsiloxane fluid/silicone resin/silica materials useful 
in the present compositions as antifoam agent can be prepared in the 
manner disclosed in U.S. Pat. No. 3,455,839. Preferred materials of this 
type comprise: 
(a) from about 10 parts to about 100 parts by weight of a 
polydimethylsiloxane fluid having a viscosity in the range from 20 to 
30,000 mm/s at 25.degree. C.: 
(b) 5 to 50 parts by weight of a siloxane resin composed of 
(CH.sub.3).sub.3 SiO.sub.1/2 units and SiO.sub.2 units in which the ratio 
of the (CH.sub.3).sub.3 SiO.sub.1/2 units to the SiO.sub.2 units is within 
the range of from 0.6/1 to 1.2/1: and 
(c) 0.5 to 5 parts by weight of a silica aerogel, precipitated silica, or 
hydrophobic silica. Such mixtures can also be sorbed onto and into a 
water-soluble solid. 
Essentially, the antifoam of the present invention includes silica 
particles, one of an oil of mineral oil, vegetable oil, and silicone oil, 
encapsulated in a water soluble solid such as sugar or a hydrolysis 
product of starch. The encapsulated antifoam has been found to inhibit 
foaming in aqueous yeast broths of Saccharomyces cerevisiae. and at the 
same time, the encapsulated antifoams of the present invention do not 
cause severe irreversible fouling of the membranes akin to the antifoam 
formulations of the prior art. Several examples, testing procedures, and 
tables, are shown hereinafter in order to more completely illustrate the 
concepts of the present invention. Percentages of materials expressed in 
the examples, tests, and tables, are intended as weight percentages, 
unless otherwise specified. 
The antifoam can be delivered in a dry solid capsule or powder form and 
dissolved to release the antifoam. The encapsulation is achieved by 
dispersing the oil and silica into a heated sugar and water solution. The 
sugar melt is cooled and solidified entrapping the defoaming active 
moiety. The solid is broken into various particle sizes. Alternatively, 
the melt can be dried and formed into microparticles by spray drying. The 
antifoam can be used in fermentation broths to inhibit foaming without 
causing fouling of the ultrafilters used in enzyme concentration 
downstream of the bioreactor. Contact with an aqueous solution causes 
dissolution of the sugar encapsulator releasing the antifoam. 
EXAMPLE I 
A solution of 30-35% maltodextrin and 30-35% water was heated with stirring 
until the maltodextrin melted and dissolved in water. A solution of 3-10% 
vegetable oil and hydrophobic silica was added. The mixture was heated and 
stirred until the oil and silica were dispersed. The mixture was poured 
onto a silicon-treated paper and allowed to dry overnight. The hardened 
crystalline material was broken into various particle sizes. 
EXAMPLE II 
A solution of 30-35% maltodextrin and 30-35% water was heated with stirring 
until the maltodextrin melted and dissolved in water. A solution of 3-10% 
mineral oil and hydrophobic silica was added. The mixture was heated and 
stirred until the oil and silica were dispersed. The water was removed via 
spray drying, and the powder and granules were collected. 
Table I shows compositions A-D prepared in accordance with Examples I and 
II. 
TABLE I 
______________________________________ 
A B C D 
______________________________________ 
Maltodextrin* 
63.63% 60.00% 60.00% 
65.57% 
Water 30.91% 35.00% 5.60% 30.16% 
Soybean oil 4.55% -- -- -- 
Mineral oil -- 4.00% 4.00% 3.94% 
Hydrophobic silica 
.91% 1.00% 0.40% 0.33% 
______________________________________ 
*=Manufactured by A. E. Staley Mfg. Co., Decatur, Illinois, and sold unde 
the Trademark STARDRI .RTM.. 
The defoaming efficiency of compositions A-D prepared above in Examples I 
and II, and shown in Table I, was determined by using a one thousand 
milliliter graduated cylinder, equipped with a gas dispersion tube 
terminating in a stone sparger. Two hundred milliliter samples were loaded 
into the cylinder and an air flow rate of five hundred milliliters per 
minute was used to sparge the contents. The contents were sparged with air 
continuously while at the same time measuring the foam height at each 
fifteen second interval. The control sample included two hundred 
milliliters of deionized water containing three percent by weight of S. 
cerevisiae, but containing no antifoam agent. The yeast S. cerevisiae was 
added to simulate a fermentation broth. Test samples including twenty-five 
parts per million of each of antifoam compositions A-D, were prepared in 
two hundred milliliters of deionized water containing three percent by 
weight of S. cerevisiae, and sparged as indicated above. The results of 
such tests of the defoaming ability of the encapsulated antifoams of the 
present invention can be seen in Table II. 
TABLE II 
______________________________________ 
Foam Height (ml.) 
Time(sec.) 
Control X* A B C D 
______________________________________ 
15 500 400 400 300 340 450 
30 670 500 440 330 320 450 
45 760 650 400 350 310 470 
60 770 650 350 350 310 400 
75 750 800 350 350 300 350 
300 -- &gt;1000 300 350 300 300 
______________________________________ 
*=Polygloycol based antifoam for comparison. 
In Examples III and IV set forth below, additional encapsulated antifoams 
were prepared including silicone based oils. Compositions E-G prepared in 
accordance with Examples III and IV are shown in Table III. In Table III, 
compound Y is a polydimethylsiloxane fluid having a viscosity of about 550 
centipoises measured at twenty-five degrees Centigrade, and including a 
silica filler. Compound Z is also a silica filled polydimethylsiloxane 
fluid but of a viscosity of about 1200 centipoises. The defoaming 
efficiency of these encapsulated silicone antifoam formulations E-G was 
tested in accordance with the procedure outlined hereinbefore, and the 
results of such defoaming tests is shown in Table IV. 
EXAMPLE III 
A solution of 55-95% maltodextrin, 5-30% silicone antifoam compound and 
1-35% water was heated with stirring until the maltodextrin melted and 
dissolved in water. The solution was poured onto silicon-treated paper and 
allowed to dry overnight. The hardened crystalline material was broken 
into various particle sizes. 
EXAMPLE IV 
A solution of 55-95% maltodextrin and 30-35% water was heated with stirring 
until the maltodextrin melted and dissolved in water silicone antifoam 
compound, 3-10% by weight, was added. The mixture was heated and stirred 
until the compound was dispersed. The water was removed via spray drying, 
and the powder and granules were collected. 
TABLE III 
______________________________________ 
E F G 
______________________________________ 
Maltodextrin* 
60.0% -- 57.14% 
Maltodextrin** 
-- 62.5% -- 
Compound Y 5.0% 20.83% -- 
Compound Z -- -- 14.29% 
Water 35.0% 16.67% 28.57% 
______________________________________ 
*=See Table I. 
**=Sold under the Trademark MALTRIN .RTM.. 
TABLE IV 
______________________________________ 
Foam Height (ml.) 
Time(sec.) Control E F G 
______________________________________ 
15 500 300 450 325 
30 670 300 550 400 
45 760 350 600 450 
60 770 350 600 450 
75 750 240 600 450 
______________________________________ 
It has been found in accordance with the teaching of the present invention, 
that any membrane fouling which may occur, is reversible, and that the 
ultrafiltration membrane surface can be cleaned. Such cleaning may be 
accomplished by passing through the membrane about ten liters of 0.1M 
sodium hydroxide solution, or about ten liters of 0.5 weight percent of 
TERGAZYME.RTM. enzymatic cleaner, for fifteen minutes. Two ten liter 
volumes of clear deionized water are flushed through the system following 
this treatment. 
While particular weight percentages of ingredients of the encapsulated 
antifoams are set forth in Examples I-IV, the compositions of the present 
invention are not limited to such amounts, and the various ingredients may 
be employed in other and varying percentages. For example, maltodextrin 
may be present and can constitute from about 55-95 weight percent of the 
encapsulated antifoam formulation. The silica filler can be present and 
may constitute from about one to about nine weight percent. The siloxane 
fluid is preferably employed in the amount of from about three to about 
twenty weight percent; while vegetable oils and mineral oils can comprise 
from about five to about thirty percent by weight. 
In the following table, data are set forth indicating results obtained from 
tests conducted for the purpose of determining fouling and clogging which 
may occur as a result of the presence of several antifoam formulations in 
a solution of deionized water containing about one hundred parts per 
million of antifoam formulation. A membrane constructed of a polysulfone 
material in sheet form and having an approximate molecular weight cut off 
of about 25,000 was employed. The table expresses the percent relative 
flux obtained during such tests as a function of the time in minutes which 
elapsed, in order for fifty milliliters of filtrate to be collected 
through the membrane. The flux following cleaning of the membrane, is also 
reflected in Table V. As noted previously, flux is an expression of 
filtration rate, and the most ideal flux is related to the value obtained 
when pure water, free of antifoam agent, is passed through the membrane. 
Solutions containing encapsulated antifoam formulations prepared in 
accordance with the present invention, as well as comparitive antifoam 
formulations, are shown in Table V. 
TABLE V 
______________________________________ 
% RELATIVE FLUX* 
Filtration Control 
Time(min.) (Water) A X*** F 
______________________________________ 
0 100 100 100 100 
30 91.0 87.6 23.7 80.4 
60 91.0 87.6 23.7 74.3 
90 88.8 87.6 23.7 75.4 
120 82.1 82.3 23.2 69.0 
Flux after -- -- 73.1 87.5 
cleaning** 
______________________________________ 
*The initial permeate flux of deionized water was measured and considered 
100%. The permeate flux was measured at 30 minute intervals after additio 
of antifoam and compared to the initial flux. 
**The membranes were treated with TERGAZYME .RTM., an enzymatic cleaner, 
for ten minutes, rinsed with deionized water and the permeate flux 
remeasured. 
***Polyglycol based antifoam for comparison. 
It will be apparent from the foregoing that many other variations and 
modifications may be made in the structures, compounds, compositions, and 
methods described herein without departing substantially from the 
essential features and concepts of the present invention. Accordingly, it 
should be clearly understood that the forms of the invention described 
herein are exemplary only and are not intended as limitations on the scope 
of the present invention.