Note: Descriptions are shown in the official language in which they were submitted.
~57Z~
The invention of this application relates to the con-
version o~ starch to levulose, and in particular, to such
conversion which is effected wholly by enzymes.
Starch is a polymeric carbohydrate material of very
high molecular weight. Its monomeric units are termed
anhydroglucose units, and the complete hydrolysis of starch
yields dextrose, Dextrose in turn is susceptible of iso-
merization to levulose, either by alkaline or enzyme catalysis.
The latter is of increaslng importance at the present time
becau~e of recent improvements in the conversion of dextrose
to levulose by means of enzyme catalysis.
Of all the "sugar" consumed throughout the world,
sucrose is by far the most commonly used. It is what is --
commonly known as table ~ugar. It is a remarkably stable
product and has very good sweeteninS~ properties. It is not
entirely without shortcomings, however, because at high - -
concentrations it does tend to crystalli2e and thus 1~ -
adversely affects the texture and appearance of foods in
,
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~hich it is colltained. Fur~:hern~re9 ~ &e~n2~s i~ sald b~,r some
to lack depth and full~l~s~. De~t~o~e i~ a~ alL~rrl~tl~fe, ~ut dPYcl:ro~e
lacks the high degree oE sweetne~s whlch charac~erize0 sucro~e.
Dextrose is generally rated as being ~bout 60 to 80% as ~weet a~
sucrose and the price a~ which de~tro~e i~ ~old iB COrrespOndil~gly
lower than that of sucrose. Ilke sucro~e, desctrose tends to crystalli~.e
easlly .
Levulo~e, oll the other hand, i~ even sweeter than ~ucrose, a~d
it does no~ have the undesirable tel~dency to crys-~alli~e readily.
Unfortunately, levulose does not occur naturally in
large quantitieC~ andits preparation has heretofore been difficul~. Its
preparatlon from sucrose by hydroly~is with hydrochlorlc acid or with the
en~yme invertase has long been known a~d this hydrolysl~ produces
so-called invert sugar, half of whlch L~ levulose and -~he other
half of which i8 dextro~e.
The overaLl coll~ersion oE starch ~o :Le~uLoRe ordinar-lLy
involves three principal, separate ~tepa: a thinning oE the Jtarch,
`~ followed by saccharification, follo~Jed in turn by lsomerizatlon.
In the Eir~t step, an aque.ous slurry o~ c~tarch i~ heated to
20 gelatini~e the starch, and simultaneoualy, trea~d with an alpha- -
a~yla~e or acid, to convert it to an inter~edlate hydroly~is produc~
~having a considerably reducad vlscosity with respect ~o ~ha~ of -
I the origi~al pasted aqueous starch miltture. Then, in ~he second
s~ep, this intermediate hydrolysis produc~ ls saccharified, l.e.,
i 25 conver~ed to dextro~e by treatment ~i~h a ~accharifyin~ eIIzyme~ i.e., ~ -
,~ a glucoa~yla~e, In the third s~ep~ ~hi~ de~tro~e prod~lc~ 1~
' '"' '
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treated with an i60merase wi~h the re~ulti~g forma~lon of a
product con~aining about hal.f de~ftrose and half levulo~e, or wlth
a ba~e such as sodium hydro~ide ~o produce a product containing
a maximum of about 30~ levulose.
S Each of the above ~teps are carried out under different
conditlons of pll and temperature, 80 as to op~lmlze the efflciency
of each step. Th~s, it i8 necessary to make significant ad~ustments
in these conditions at ~he conclu~ion oP each step, with the
ref3ults that the overall efficiency of the profes~ i3 conf~iderably .
diminished. ~;
It is accordingly a pri~cipal obJect of the present invention
~, to provide an improved process for the conversion of starch to
levulo~e.
.
', It is another obJect of the pre:sent invention to provide ~uch
; 15 a process which results in high yields oi. levulose.
It is another objec~ of the pre3ent invention to provide
~uch a process which ls characterized al~o by rela~ively low
temperatures.
It is yet a~o~her object of the present invention to provld~
such a process which can be carried out conveniently and economically
I ~ in one f ~ep.
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These and other objects are accomplished by the `
process of converting starch to levulose comprising forming
an aqueous slurry of granular starch, bacterial alpha-amylase,
glucoamylase, and glucose isomerase at a temperature of from
about 40C to about 70C, and below the initial
gelatinization temperature of the starch, and at a pH of
from about 5.0 to about 7Ø Such process accomplishes the .
above objectives largely because of the combined synergistic ; :
action of the bacterial alpha-amylase, glucoamylase and glucose
isomerase which results in efficient production of levulose ~ .-
at a single temperature and pX.
: In the present invention the glucose isomerase is
derived from a source other than Stre~tomYces albus. ..
,, ~ .
In the process the temperature and pH conditions :
are maintained during enzymatic action so that insoluble or
unsolubilized starch retains its essentially granular or .::~
ungelatinized form while a soluble starch hydrolyzate
contain.ing levulose is produced, whereby any residual ..
insoluble starch remains in essentially granular
ungelatinized ~orm.
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The starch may be any of those commonly available
- including corn starch, waxy maize, tapioca, potato starch, white
sweet potato starch, wheat starch, sago, sorghum and the like.
Waxy and the non-waxy starches are suitable. As indicated, ;
the starch is granular. Corn grits and other raw mat~rials high
in starch content may be used satisfactorily. Corn starch is
a preferred raw material because of its ready availability.
An important advantage of the process is that it
may be carried out in an aqueous slurry at relatively high
concentrations. The solids content of the starch slurry
generally is within the range of from about 10% to about
70/0 ordinarily, the solids content will be 20-500/o,
Lesser concentrations can of course be used, and in
general as the concentration is decreased, so is the xtent
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i of ~.tarch solubillz~tjo~, and th~l~ Lhe yle:Ld o~ levlsl~e i~ -
increased. As a practical ~la~ter9 hGweverD -lt 1~ hlghly de~irabl.
in most instances to use ~ all ~Ol~e~9 i~e.~ hlgh concentrations
of starch. This avoids or a~ least dlminlshes ~he conslderable
expense of concentrating the con~er~ion rnl~t~re prior to ultimate
separation of lew lose. In s~Ae ca~e~, however9 the advantage of
a higher yield may be suffici~nt to ou~weigll thl~ di~ad~an~age3 ~-
and a concentration of about 10~ sollds ~ould be preferred.
The process herein pe~aits the ~olubilization of 90~ ;
or more of the starch in a 30-40~ aqueous 61urry. Furthe~more,
the undissolved starch can be recycled 80 as to improve the -~
overall efficlency; i.e., to solubilizie the previously undissol~ed
starch and thereafter to convert it to levu].ose. An incidental
15 advantage of such recycling ~tep i~ ~he~ fact ~hat a signiflcant
proportion of enzyme ac~ivity iB thUg 51l90 recovered. The
i aolubilized s~arch thus obtained ha~ a de~2;rose equlvalent (V.~.)
of 90-95. The term "D.E " is used ~o indicate the reducialg
sugar content of the isomerized hydrolysate 9 calculated as de~trD~e,
and expressed as percent by weight o~ the d~y substance pre~ent.
The bac~erial alpha-amyla~e preferably i~ one which i9
active at a relatively low p~, i.e., within the range of from
about S.0 to about 7.0, and al~o at relati~ely low ~eD2peraturesp
i.e., below the temperature at which a par~icular ~tarch gelatinlze~
Pre~erred sources of such alpha~S~2yla~es include cer~aln ~pecies
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of the Bacillus microorganism, viz., B. subtillis, B. licheni-
formis, B. coaqulans and B. amylolique~aciens. Suitable alpha-
amylases are described in West German Offenlegungsschrift
2,025,748 and in U.S. 3,697,378. Especially suitable amylases
are those derived from B. licheniformis as described in the
above German Offenlegungsschrift. Particularly preferred is
that alpha-amylase derived from B. licheniformis strain
~CIB 8061, other specific microorganism include B. licheni-
formis strains NCIB 8059, ATCC 6598, ATCC 6634, ATCC 8480,
ATCC 9945A and ATCC 11945. One such alpha-amylase preparation
is identified by the trademark "THERMAMYL", available from
~ovo Terapeutisk Laboratorium, Copenhagen, Denmark. THERMAMYL
i9 characterized by the following properties:
(a) it i9 thermally stable;
(b) it has a broad range of pH activity' and
(c) its activity and heat stability are independent
of the presence of added calcium ion.
Analysis of a suitable preparation is as follows:
- Dry Substanc~, % 94.6
Alpha-amyla e activity, U~g (as is) 9,124
Protein, % d~bo 21~2
Ash, % d.b. 1 64.4 -
~ Calcium, % d.b. ~ 4.9 ~ -
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Other suitable alpha-amylases include THERMAMYL 60*
(a liquid) and THERMAMYL 120* (a solid) having the following
analyses:
THERMAMYL THERMAMYL
60* 120*
Dry Substance, % 35.4 98 8
Alpha-amylase activity, U/g ~as is)1,156 2,105
Protein, % d.b. 26.5 21.2 ~
Ash, % d~b. 60.1 91.2 ~-
Calcium, % d~b. 0.04 0 72
Sodium, % d.b. 12.3 12.2
Still other suitable alpha-amylases which are avail-
able include ~he ~ollowing:
TABLE I
Enzyme
Preparation Company FormActivity
Rhozyme H-39* Rohm & HaasPowder4,874 ~/g
Takamine HT-1000* Miles Powder 3,760 ~/g
Tenase* Miles Liquid2,043 ~/ml
Dex-Lo MM* WallersteinLiquid1,213 ~/ml
~ovo SP-96* ~ovo Powder7,310 ~/g
, ! ~ :
No~o B. substillis* Novo Liquid1,599 ~/ml
Klei3tase GM-16* Daiwa KasaiPowder 26,593 ~/g
Kleistase L-l* Daiwa KasaiLiquid1,918 ~ml
Rapidase SP~250* SocietePowder 11,655 ~/g
"Rapidase" `~
France
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The ~nount of bacterial alpha-amyla~iP to be ueed
range~ from about 1.0 to about 25 unit~ per gram of ~arch (dry
basis). The use of larger amounti~ pro~ide~ no practical
advantage; the increased starch solubilization ~hich result~
S from ~he use of more ~han 25 units per gram does ~ot ~ustify
the additional cost of en~yme.
The alpha-amyla~e activlty oE an enz~me 18 deter~ined
as follow6:
The enzyme is allowed to react with a standard ~tarch
solution under controlled conditions. Enzyme activity i~
determined by the extent o starch hydroly~is, a~ reflected by a
decrea~e in iodine-staining capacity, which i8 measured spectro-
photometrically. The unit of bacterial alpha-amylase activity
is the amount of enzyme required to hydro:Lyze 10 mg. of starch per
lS minute under the condi~ons of the procedwre. The method is
applicable to bacterial alpha-amyla~es, including industrial
preparationsl except materials which possa~s slgnificallt
~accharlfying activity. ~ ~
.~ ', .. .
,' From 0.3 to O.S grams of solid sample or from 0.3 to 1.0
20 ml. of a liquid sample i~ di~olved ln a ~ufficent quantity of ~-
O.00~5 M aqueous calcium chloride to give an enzyme ~olution
containing approximately 0.25 uni~ oE ac~ivit~ per ml.
,}~
' A mixture~of 10 ml. of 1~ Lintner starch qolution,
`1~ equilibrated to 60C, and 1 ml. of the enzyme s~mple ~o be
tested i8 mixed and held in a 60C constant te~perature bath
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for exactly lO mil~u~e~. A l~ L. satDple l~ r~ oved a~ld added
to a mixture of 1 ml. of 1 M aqueousi hydrochlo~lc iacld a~i~d about
50 ml. of distilled water. The iodine--stalning capacity of such
acidifled sample then is determined by adding 3.0 ml. of 0.05~
aqueous iodine solu~ion, dilutlng ~o 100 ml. with dis~illed ~ater,
and msxing well. The absorbance of the solution, relati~e to that
of distilled water, is measured at 620 nm9 in a 2-cm. cell. A
similar measuremen~ i8 made of the standard starch soLution (to
which water is added instead of the enzyme solution) to provide
a blank absorbance.
The en2yme activity, in unlts/griQm or /ml. is equal
to
(Blank Absorbance - Sample Absorbance) ~ Dilution Factor x 50
Blank Absorbance x 10 x 10
The glucoamylase may be any of the well-known amylase
I preparations, particularly those derived from members of the
I Aspergillus genus, the Endomyces genus, amd the Rhizopus genus.
~ '~
A particularly preferred glucoamylase i5 tha~ available from the
process de~cribed in U. S. 3,01i2,584 (Kooi et al) whereby a fungal
amylase preparation is freed of undesired transglucosidase activity
by treatment in an aqueous mediu~ with a clay mineral. The amount
i of glucoamylase to be used ranpes from about 0.1 unit to about 5.0
unies per gram of s~arch (dry basis). Prefe~ably, on an enzyme
cos~/performance basis, about 0.25 unit o~ glucoamylase per gram
. ~,
l 25 of 9tarch (dry basis) iB used.
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Glucoamylase activity units are determined as follows:
~he substrate is a 15-18 D.E. acid hydrolysate of
corn starch dissolved in water and diluted to 4.0 grams of dry
substance per 100 ml. of solution Exactly 50 ml. of the ;
solution is pipetted into a 100 ml. volumetric ~lask. To the
flask is added S.O ml. of 1.O molar sodium acetate-acetic acid
buffer (pH: 4.3). The flask is placed in a water bath at 60C
and after 10 minutes the proper amount of the enzyme preparation
is added. At exactly 120 minutes after addition of the enæyme
preparation the solution is adjusted to a phenolphthalein end- -
.: . . .
point with ona normal sodium hydroxide. The solution is then
cooled to room temperature, and diluted to volume. A reducing -
~ :-.
sugar value, calculated as dextrose, is determined on the
diluted sample and on a control with no enzyme preparation added.-
, .
Glucoamylase activity is calculated as follows: ~
A = 2 X E ;
where
A = glucomylase artivity units per r~. (or per gram) of enzyme
; 20 prepara~ion
S - reducing ~ugars in enzyme convartad sample, grams per 100 ml
.:
B - reducing sugars in control, gram~ per 100 ml.
E = amount of enzyme preparation used, ml. (or grams) "S" should
not exceed 1.0 grams per 100 ml.
The isomerase may be any such,enzyma capable o~ con~
verting dextrose (~lucose~ to levulose (fructose). It will be
underatood, thare~ore, that in this specification isomerase or
glucose isomerase refers to enzymes c~pable of co~verting
dextrose to levulose, even though this might not be the primary
function of the enzyme, on the basis of which it is classified~
hus glucose isomerase is to be understood as embracing xylose
isom~rase. Many are presently known including principally
~ ... .
~L~)S7Z~IL9
those elaborated by microorganisms of the Streptomyces genus,
for example, S. bobiliae, S. fradiae, S. roseochromoqenes, S.
olivacens, S. californicus, S, vinacens, S. virqiniae, S.
olivochromoqenes, and S. p--aeochromoqenes; a particular pre-
-ferred glucose isomerase is derived from S. albus YT-No. 5
(ATCC No. 21,132), the process employing this glucose isomerase
being the subject of commonly assigned Canadian application
S.~. 220,946, Raoul Walon, filed Febluary 26, 197S. Isomerases
elaborated by microorganisms of the Arthrobacter genus likewise
are contemplated, e.g., A. nov. sp. ~RRL B-3724, A. nov. Sp,
NRRL B-3725, A. nov.~p. ~RRL B-3726, A.nov~ sp. MRRL B-3727
and A~ nov. sp. NRRL B-3728. So also, isomerases elaborated ~ ~
by microorganisms of the Lactobacillus genus, e.g., L. brevis, - ~-
k. mannitopens and k. buchneri. Also, Aarobacter cloacae and
A, aero~enes. ~ ~-
The amount of isomerase to be used ranges from
about 0.1 unit to about 20 units per gram of starch (dry basis). -
In the usual, preferred instance, an amount within the range
of from about 0.2 to about 2.0 will be used.
I~omerase act-vity units are determined as follows: -~
The procedure involves making a spectrophotometric -~
determination of the ketose produced from a glucose solution
~; under a standardized set of conditions.
The enzyme preparation ~o be assayed is first diluted
to contain from 1 to 6 isomerase units per ml.
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~57Z~
A stock solution is prepared as follows:
Component Amount
0~1 M MgSo4.7H20 1 ml.
0Ø M CoC12.6H20 1 ml.
1 M Phosphate Buffer, pH 7.5 0.5 ml.
Anhydrous D-glucose 1.44 g.
Distilled Water To make up a total volume
of 7.5 ml.
An enzymatic isomerization is conducted by adding 1 ml~
of the enzyme preparation to 3 mlD of the stock solution, then
incubating it for 30 minutes at 60C. At the end of this ~
incubation period, a l-ml. aliquot is taken and quenched in ~ -
9 ml. of 0.5 N perchloric acid4 ~The quenched aliquot then is
diluted to a total volume of 250 ml. As a control, for
comparative purposes, the procedure is repeated substituting 1 ml.
of water for the 1 ml. of the enzyme preparation in solution
form~ at the beginning of the incubation period. ;~
The ketose then is determined by a cysteine-sulfuric
acid method. See Dische et al, J. Biol. Chem. 192, pg. 583 (1951).
For the purposes of this assay, one isomerase unit is defined ~ -
as the amount of~enzyme activity required to produce one micromole
of levulose per minute under the isomerization conditions described.
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~572~g
The temperature of the reaction mixture of the
process herein should as indicated be from about 40C to about
70 C. Ordinarily, the temperature will be at the upper end of
this range, ConsiStent with the requirement that it be below
the tempera~ure at which the starch is gèlatinized. A particular
advantage of the process is the fact that high temperatures are ~
avoided. This permits a considerable savings in the cost of -
supplying heat to the process and minimizes the formation of
color bodies with a subsequent savings in refining costs. -
The selection of pH depends upon the particular
enzymes used in the process. Ideally, the thinning, saccharifying
and isomerase enzymes would exhibit their optimum activities at
about the same pH, but as a practical matter this is unlikely.
Glucoamylase is of course the saccharifying enzyme and its optimum
activity is in the range of 3,5 - 5.0 pH. Alpha-amylase's optimum
activity is~at a pH within the range of 5.5 - 7 and is not
sufficiently active at a pH below 5 to promote the desired starch
solubilization. The isomerases generally are most active at still
higher pH~s, e.g.9 in the order of 7.0 - 9~0. It is thus unexpected
to find that all three of these enzymes will act cooperatively at one
pH~ as in fact they do. ~A suitahle pH for the purposes of the
invention herein is one falling within the range of from about S.
to about 7~0.
The hydrolysis mixture should contain magnesium and
cobalt ions. These may be supplied in the form cf magnesium
sulfate hexahydrate (MgS04.6H20~ and cobalt chloride heptahydrate
~' (CoC12.7H20~. The amounts of these salts or of other water soluble
-14_
.
:
~L~572~
magnesium and cobalt salts, should be such as to provide from
about 0.005 to about 0.10 moles per lit~r of magnesium and from
about 0~0001 to about 0.005 moles per liter of cobalt ions.
These ions in these concentrations enhance the activity of the
isomerase and appear not to have an adverse affect on the
activity of the other enzymes.
Although the calcium ion is known tv have a beneficial affect
on the activity of alpha-amylases, it is unnecessary to add it to
the conversion mixtures of this invention and, in certain preferred ~ -~
instances, it is advisable not to add any because it appears to have
an adverse effect on the activity of the isomerase and, correspon~ingly,
on the ultimate yield of levulose.
As shown in Example 1~ 73% of the starch is solubilized
in 18 hou~s, with a yield of 29.3% (of the solubilized starch) of
levulose. At 42 hours~ the correspondlng figures are 81GL
solubilized starch and 36.3% levulose; and at 67 h~ours, the
i corresponding figures are 91% and 38.9%, In example 2, over 98%
of the starch is solubilized at 48 hours and 40.7% of this
solubilized starch has been converted to levulose.
The invention is illustrated in some detail by the
~"hi .. ' . ~ ~. .
following è~amples which, however~ are not to be taken as limiting
in any respect.
~` 13XAMPLE 1
To a 32.7% (18.4 Baumé) aqueous suspension of granular
corn starch there is added 0.01 mole of magnesium ion (as magnesium
.
! 15
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~V57~
sulfate he~cah~dra~f~) and ~oOOl IDole u col~al~: loil ~a~ collal~ou3
ch.l.orlde heptahgdrate) and the pH ad~ t:e~ 507. Sotll~m
carbonate (a one no~lal aql~20us aolut:lo~) J.~ added a~ nece~sa~y ~o
maintain the pH at this :Level. l~e tta~pera~urP i~ maintained at
60C and 0.075% (6~8 ac~ ity unlts per gram of ~ta~ch), O.lX
(0.2 activity unit pe~ ~ra~ of starch) of gl~lcoai~yla~e and 0.8
(0.33 activity Uilit~ per graul of st~rch) of isomerase (Strepto~ ce~
albus YT-5) are added. The following r~ults were obtained:
10 Time (Hou~s) i 18 42 67
D. S. in Filtrate 24%Z6.4% 29.8%
~. ~. of Filtrate 93.6Z 94.4% 94.1%
; Levulose in Filtrate 29.3~* 36.5~* 3~.9%~
Dextrose in Filtrate 62%* 57.4%* 53.8%~
15 *based on solids
The soluble fraction is of course the filtrate obtained
upon fil~ration of the conversion mi~ture. The filtra~ion proceed~
easily because there is no gelatinized ,starch in the con~ersion
mixture. The amount of granular starch ob~ained after the
oompletion of the reaction as above, amoun~ed to 4~ of the whole.
!~ ~ E~AMPLE Z
To a 40.9% (23 Baumé) aqueou~ su~pen~ion oE granUlaL^
corn starch there i~ added cobalP ion and magnesium ion as in E~a~ple
1. The pH is adiu~ted at 5.7 a~d ~aineained at this level ~hroughout
J~
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~he con~erslon by the ai1rlil:Loll c~f ~ oi~e ~omi~lJI 30sl:LIml carbo~Lu~
solutlon aFJ needed. 'l'he ~empera~ure i~ maln~aln d a~ 60~C and
0.15% (13.7 acti~ity Imi~s per gralll of ~tarch) of ~HE~L alpha--
amylase, 0.1% (0.2 actl~lty unlt pe~ gram of ~tarch) of gluco~myla~e
and 0.8% (0.33 activity ~mit per gr~m of ~tarch) of i~omera~e
(Streptom~ce3 albu~ YT-5) are added. The ~lurry iFI kept at 60C for
48 hours, then filtered. The iltrate is characteri~ed by ehe
following analytlcal data:
D.S. 40.2%
D.E. 91.5%
Levulo~e 40.7%*
De~trose Sl~*
Ash (% Sulfate d.e.) 0.35%
Starch Test Negative
based on solid~
. ~
~XAMPI.E 3
'
A 25~ by weight aqueous slurry of granular corn s~arc`l
i8 prepared con~aining the followlng ingredients:
125 g. oE corn starch
'~ 250 ml. of 1.0 N aqueou6 potassium phosphate buffer, p~: 7.5
S ml. of 1.0 N magne~ium ~ulfate he~ahydrate
, ~:
~ 5 ~1. of 0.1 N cobalt chloride heptahydra~e
,
Sufficient aqueous calcium chloride to provite 100 ppl~l of
' 2S calcium ion
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~L057~
Alpha-amylase (Bacillus licheniformis, S
activity units/g of starch (dry basis))
Glucoamylase (1,0 activity units/g of
starch (dry basis))
Isomerase (Streptomyces olivochromo~enes,
10 activity units/g of starch (dry basis))
The above aqueous slurry is maintained at 60C for
24 hours, the pH being adjusted to 6,0 as necessary by additions
of aqueous potassium hydroxide, The conversion rnixture is
filtered and the filtrat~ adjusted to a pH of 4.5 by the
addition of hydrochloric acid, then boiled to inactivate the
enzymes, The solids material comprises 44,~/O of the original
granular stiarch, which means that 55,1% o~ the granular starch -~
is solubilized, This solubilized starch product is found to
have a dextrose content of 51,2% and a ketose ~levulose)
content of 20.6%, both based on solids content.
EXAMPLE 4
The procedure of Example 3 is repeated except that
the pH i9 maintained at 6.5 throughout, The proportion of
~tarch solubilized i9 48~/o and the dextrose content of that
soIubilized portion is 36,1; the ketose (levulose) content is
23.~b.
All parts and percentages herein unless otherwise
expressly stated are by weight. --
The following enzyme numbers may be of assistance
~, 1n~reading the disclosure and claims:
alpha amylase E.C.3,2,1~1,
glucose isor~rase E.C,5,3,1.18.
~: :
xylose isomerase E.C,5,3.1,5,
~; 30 ~ ~ glucoamylase E.C.3,2,1.3,
It wil} be understood that according to the
classification system an enzyme is named according to it~
primary functlon, although it r~y display more than one
function,
18 - ;~
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While the invention has been described in connection
with specific embodiments thereof, it will be understood that
it is capable of further modification, and this application
is intended to cover any variations, uses or adaptations of
the invention following, in general, the principles of the
invention and including such departures from the present dis- ;
closure as come within known or customary practice in the art
to which the invention pertains and as may be applied to the
essential features hereinbefore set forth, and as fall within :
the scope of the invention. ~
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