CA2038485A1 - Nanofiltration process for making dextrose - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A nanofilter membrane is used to filter the outflow of a food processing stream which begins with a starch slurry and ends with a glucose syrup which is about 95% dextrose and 5%
di- and trisaccharides. the nanofilter membrane is able to pass the dextrose while retaining the di- and trisaccharides.
As a result, the invention is able to produce substantially pure dextrose, with purity in a range which is well over 99%.

Description

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~ANO~ATION PROCES~;;ENG DExq~osE
This inqention rela~es ~o nanofiltration of a food p~o~es~ing feed ~trea~ -- especially but not exalusivfaly --~or ~he production o~ dextrose.
Evap~ration, ~ree~e c~oncent~ation, or ~reeze dryihg are c:o~nmon dewatering techniques u~ea in ~e food, phan~aceutical and l~iological processing industr~e~. Evap4ration requires the input o~ a~ut l000 Bq~J ~or each pound of ~lrater that is evapo~a.ted (540 ~c:al/kg) while ~reez~ng re~uires al~ou~ 1~4 ~U
for eac~ pound o~ water $rc~e2l, ~uerely to ef~eot the ~han~e in state o~ water ~XOffl li~uid ~o ~vapor or liguid to solid, re~pectively.
Since men~rane ~iltxation doe~ not reguire a change in ~tate to ef~ec~ dew~tering, it should result in ~on~iderable savings in enerS~y. A les~: ol~viou~; ad~antage is the ~ t that no ~ompl~cate~l heat trans~er or he~t-generating ~quip3nent i$
nee~d~ Only electrical energy i~ required to drive a pu~p mctor. Ano~her advantag~ is t~at me~brane filtration can b~
carried out a~ amb~ent or lower temp~ra~ures (e.g.~ to prevent ~icrobial growth pro~lem~ or denaturation o~ heat sensitiv~
¢~ponents) or at higher tempera~ures te.g., to ~ini~i~e m~crobial g~o~th problems, to lower vi~cosity of t~e retentate thU~ lowering pumping C08t~, or ~o improv~ ma~8 tran~e~
Since small ~oleoules~ should nor~nally pa~ reely through filtrati~n m~mbrane~, the~r concentrati.on on either side o~
~he membrane should be abou~ the ~ame during proce~n~ and a~out e~ual ~0 ~he original ~eed ~lu~ion~ Thus, ~ rane filtration o~e~ many advantage over othe~ dewaterin~
proce~ses.

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A l~ok entitled "~ltrafiltration ~and)~oolcU by ~u~ir Cheryan, published by Technomics Publ:ishing Co., Inc. ~51 New Holl~nd~ Ave., Lancaster, PA 17~04 U.8.A. d~cribes membrane filtration as a sepaxat~on o~ two or l~ore ~omponents ~rc-m a S fluid strea~. A membran~ i:; a ~;ele:s~iv~ l~arrler whiah prevents ma~;S moVen~nt, ~ut ~llows res~ricted or r~ulated paS~sage, o~ one or more S2p~cieC through it:. Me~rane f iltr~tion inc:lude~ the use Of ~UCh a ~axrler tC~ pa~s certain compon~3nts while retaining s~ertain other compon~n~s o~ ~
10 mix~:ure in order '~;o s:eparat~ dis~olved solu~:es in liguid streams~.
Membranes can be alas;si~ied by their porous vs. nonpoxous s3tructure. o~;~osi;; involve a mov~ment of a ~iolvent fxom the dilute solu~io~ side through a semi-permeable m~mbrane to ~he 1~ aoncen~rated solution side ~f the ~e~brane, responsive ~o ~h~
chemical poten~ial diffe~nce bet~een the water on either &ide o~ ths ~embrane.
Five other ~jor me~brane 3eparation processes are reverse os~oSi~, o~ ultra~îltration, microfiltra~ion, dialysis and electrodialy~i~, w~ich cov~r a wide range ~f par~icle ~izes~ Rever e o~mosis or ultr~filtration per~it a separation o~ di3~01ved m~le~uleæ down to the ionic range. Reverse osmo i~ or hyper~iltratio~ relate~ ~o dew~ering while ultrafiltratîon simult~neou61y purif iQS ~ ~y ¢on~entxating, and ~5 fraction~tîng macro~olecules or fi~e colloid~l susp~nsion.
Reve~e ~s~o~is or hyperfiltra~i~n ret~îns mo.ttnsarly all compon~nts other than the 801vent twater) its~lP, while ultrafiltration retains only th~ ~acromolecules ~r parti~les 2 ~

larger than about 10-200 Ao ~l~raYiltration only needs a ~airly low pre~r~ ~or opsration. R~ver~e o~mosi~, ultra~iltra~ion, or byper~iltration cons~i~u~e co~inuous molecular ~epar~tion pro~es~s whioh d~es not involve a pha e change~or interpha~e mass transfer~ ~hu~ making ~he~e proces&e~ important ~or food, pharmaceu~ical and hiolo~ical proces~ing~
~ r ~he~e and other reasons, i~ dvan~a~eous to use me~br~ne ~iltration i.n ~he production of certain ~oo~
pr~ducts, such as dextrose. ~ereto~ore, a drawback o~ usin~
dextrose as ~ ~he~i~al feedstock centers about the difficul~y encountered in ob~ainin~ a str~am o~ dextroR~ with a su~iciently high purity bec~u~e ~he d~x~ro~e mole~ulec must ~e separa~ed fro~ molecule~ or o~her material~, whi~h have ~lmos~ ~he ~a~e charac~eristics, ~uc~ a~ ~altose and higher oligosa~haxides. ~h~ conven~ional pro~esC ~or producing a hi~ purity dextro~e ~i.e. ~reater than 99~ purity) ~guires a co~tly and time oon~uming crygtallization o~ a very hi~hly conc~ntrated syrup. Ther2for~, a non-cry~alli~tion alternative pxo~ess is nesded to provide an ineXpensive high purity de~trose stream.
~ eretofore, me~branss have not been able to separate ¢lo~ely similar materials. Di~ ion through a reverse osmosi~ membrane i~ able to ~oncentra~e a ~tream cont~ining dextrose, ~alto~e, and salt~ in order ~o provide a puri~ed a~ueou~ ~tream, but it doe~ not purify the dextrose by re~oving the m~ltose ~nd salts. While çonventional ul~r~iltration provides means for pUri~ying or ~eparating 203~Sa ~ionle ~ermentation and chem~aal produc~s, it ç~nnot do very much ~oward sep~r~ting and purifying fairly ~:i~ilar c:ompounds, such a~ malto~e ~nd de~r~ro~e.
~ccordingly, an objççt o~ the inventi~n ~s to provide new 5 and no~el ~nea~ns ~or an~ methods ~f ~reating ,and purifying chenical feed stream~. Here, an obje~: i~ to purify feed stream~; used in food proces~3ing. In 1:hi8 connec~ion, ~n objeat is to provide ~ans for and ~nethods o~ 8ep~rat;ng and purifying dextrose feed txeamC.
Anot~h~ object ~ ~; t~ provide f~;ter, less ~xpens~Ye, and mor~a energy e~ficient mean~: ~or and method: o~ producing dextrose~ ~lere, ~n object is t~ ~;eparate dextrose fro~ its ~lo~;ely related co~ponents in a food processing feed E:tream~
In keeping with an aspect o~ ~hi8 inv~3ntiorl, the~;e and 15 o~her ol~jects are aacomplished ~y providinq a ~anofiltration ~e~r~ne at or n~ar the outp~ of a ~eed strea~n. The ~eed ~trea~ begins with a produc~ion of corn starch, pr~ceed~
through gelatinization, de~trinization, and sac~harification s~ep~ to provlde a feed stream of glucoæe eyrup. ~he fore~oing process may produce glucose ~yrup wîth a purity of about 95% ~xtrose, 5% di- and trisa~charides. The in~ention u~es a nano~iltration process in or~er to further re~ne the syrup and re~ove most of ~he re~aining 5% o~ non-dextroRe ~a~erials. After the nanofiltratlon~ the material may be con~iderably more th~n 99% pure dextr~s~.
In the atta~hed drawings:
Fig~ 1 show~ the steps in a proce$s ~hich incorporates the invention;

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Fig. 2 is a flow diagram whlc:h 3hows a sy~tem cle~ignated mo lsT~ by i~ manu~acturer o~on.ics Inc. of ~innet~nka, Minne~o~.a that was u~d to cor~duct t~s~ leading to so~e working exa~ples; ~rld Fi~ . 3 is a f low chaxt o~ a pilot system used in a plan~
whiah practice~i the invention in ordex to produce o~her working exa~aple~:.
initial steps in the particular feed s~eam sho~n in th6: att~c:he~l Fiq. 1 are ~aken ~ro~n the ~L9~
~, whieh i~ published by N~o In~u~tri A/S ~nzy~ne Divi~ion, l~ajsuP~3rd, Den~ark~ T~e ~e~d stream begins with a ~;ta~ch slurry 20 ~hic:h is produced fro~
processed c~rn. q~he slurry is exposed to an a-amylase enæy~ne at high tempera~ures (100~) which qe~a~inizes and liquefies the starch ~ part o~ a liq~efa~ion Rtep. The ~ h in the pre~enae of ~-amyla~ie i~ cooked in ~wo steps to produce ~irs~
a g&latini8~tion and then a dextrinization, as shown at 22, 24, ~n order to provide a dextrin ~3yrup which is expo~;ed to a glucoamyla:e enzyme. As part of and following thiS ~tep, there i~; a ~saccharification, as ~hown at 26, r2sulting in a, glu~:o:e ~3yrup.
This proc;~; lead~ to a qlucose symp 27 ~hich i~
al7proxi~a$ely 95~ dextro~;e and S% di- or trisacc:haridesO
Here~o~ore, th~re has ~een no easy way to elimina~e the remaining 5% di- and txisaccharides. The manu~ac~urer either sold the glucc~ e ~;yrup with the sacch~rid~ in it or performed a fur~her processing tha~ used yet ~nother enz~ss, which escalates costs.

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Acc:ording to ~e inv~ention, the need ~c-r ~ ~urther ~nzyme step may be eliDlinated by a nano~iltra~ion pr~::eæ:. More particularly" t:he gluc~o~e syrup 27 i~ passed l:hrough a nano~iltra~i~n me~ra~e 28~ This :~.ltration separate~ he 5 dext;rose ~rom ~he di- and trîsa<~ arides, and pro~uces a purer dextr~se Btream~ mu~:h ~a~3t~r and a~ le~ C08t than the pr~viously ~lded ~3teps whioh required ~urther en~yme p:roae~;ing..
In gr~at~r det~il, na~l~filtration uses a preæællre drive~n 10 membrane t~at is ~e~ween revex~e o~mosis and ul~rafiltxation me~ranes, whiah i~; ca~l~3d a ~nanofill~e~" ~em~rane. The nanoi~iltraltion rej~ction is low f~r ~s:alt with monovalerlt anion and nonionized org~ni~s ~ith Dlolecular wel~t ~ w ~50.
Rejecti~n is high for sal~ Wit}l di- and mul~i~alent ahiOnS
lg an~ organia~; with mole~:ular weight a~out 300. ~hen workirlg wi~h dilute streams or' ~lt and ~3ugars, these nanome~ ane~
retain sugars ~nd divalent ions versus monovalent ions.~
Surprisingly, we have ~ound that when u;e~1 with a highl y concentrated dextrose feed stre~, theæe nan4DIembranes yield ~0 an initial per~eate d~xtrose ~eed ~itream whicl~ has a m~ch higher purity than the o~iginal feed st~eam. Purther worlc ha~
al~o ~hown ~at when u~ed i~ a downstreaDI processing ~tep thRs~3 nanomembrane: not only r~s~ove di~acoharides and higher cac:charide:i bu~ also ~emove, ~o same extent, divalent salt~
25 ~hus provi~in~ a highly p~lri~ie~ pro~ t.
Presently Filn~req, a c:ompany loçated at ~oO O~ ; Lane, Ninn~apolisJ MN SS~3~, ha~ two commercial nano~iltration ~embran~s, ~70 ~nd NF40 (NF stands ~or n~no~ ation~ ~aoh 2 0 3 .~ ~ t~ ~

membra~e ha~ a negatîv~s ~ur~ace charg~3 which has~ not been quantifi~.
q~he f~lter membrane NF7n i~ cro~:~li~ed arc~mal:ic polyamid~. The ~ilter membranes NF~O ar~d NF70 are similar;
5 however, the me~rane ~F40 ha~3 a ~ htly lower NaCl rejéo~ion, which indicate3 that its pore~ are slightly larger than th~ pores of the NF~O meDIbrane. ~y way of example, FllmTec: de~ribe~ thei~ n~nofiltr~tion ~emb:ran~ NF70, a~
follo~;:
GENER~ SPECIFICA~IONS;
~on~i~uration Spiral Wound P~e~sure Range: 70-300 PSI
pH Range: 2 ~ 12 short term~
Max~ Feed ~emp*: 45 D~G~ c or 113 D~G F
~ rine Tolerance: 1,000 ppln-houx;s (app~ox.,) *NOTE: Not recommended to exc:eed ~axi~um operatin~
te~perature due to breakdo~n of ~aterials at l~igh tempera~ures~
E~ SPECIFIC~TIGNS: speci~ications a~e l~ased on 1,000 mg/l solute fe~d solution at 70 PSI net pressu~e, 25 ~EG.
C, 109~ recove~y, pH 5-8.

PERN Raq~E MI~ t . ~
IlC~EI:, G~?D E~C:q!ION MaS04 ~-~2540F70 600 96%
N--N4040F701800 36%
M-N80~0F70 7500 96%
PERFOR~laNCE DA~A:
INORG~NIcS: Th~ follc~insl data i~ }~A:ed on ~0 PSI net pr~4sure~ 25 ~E~:. C, 10% rec:o~rery, pEI 7-8, inorg~ni~: ~e~ections may vary with conc~ntration~

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UNITS ~~ E~ 3EC:q'ION
Sodi~ chloride mg/ l 80%
ORGANIC~ he follo~?~ ng data ls ~a~ed on 70 PSI net pre~;ure 25 ~i:G~ <~ and 10% reaovery~
~ ~OLE~ %R~.
~:lucose :mg/l sucros~ ~ng/ 1 ~8%
Lac:tosq~ mgll 98 So~e o~ the oper~ing conditions and perfor~ance~ of the LO FilmTe~ nano~i~ter membrane~a are ~hown in Table 1.
~LE 1. OPl~ATING C4~ITIO~S llND PEE~OR~NC~ 0~ 1 FII~ IE~ANES
N~70 NF4 Pres~ure to produce 1~ 43e/~2lh pexmeat~ ~ 20 f lux , bar Opera~inq p~l range 3i-~ 2-10 Nax. Te~p. ~. ~S 4S
Approxi~a~e solute 2~ ~2j~ction Na21 70 45 ~gS~ 98 ~S
Glucose (N~ 180) g8 90 Su~ro~e (NW 342~ g9 9~

2S Ano~ ~r sourc~ of nano~iltration membranes is Filtration Engineering Co. Inc. 4~7~ ~oun~y ~oad 18 North~ New Hope~
Minneso~a 5S428. F~ltration Enqine~ring describes its F~-700-002 me~brane a~ d cro~-lin~ed p~yamide, having a rejection char~oteri~tic~ W~i~h enab1es it to discri~inate among low molec~lar weight ~pe~ies~ This me~brane has rejeatio~ ch~r~teristi~s ~hich are between those com~on in rever~e o~mosis and ultrafiltratio~. The pore s~ructure of the me~rane enables a ~eparat~on be~ween ~odium ~hloride and calcium sulfate. The utili~y 0~ the ~embrane is said t~ ~e 35 ~urther enhanc:ed by t:he :~imul~neou~ ility to c:oncentrate 203~a the reta~ned spec:ie&~ ; ~ç3mk~rane give: t~e u;ers cc~n~; ~ derabl~ latitud~ in process stream par~e~er~, suc:h variations o~ pEI, ion~c strenyth, ~nd tempRratur~.
~r~e manu~acturer describes ~he Thin Film ~-700-OO~
membrane characteristias, as ~ollows:
c~po~ition: ~r~sælinked Polyamide Per~ea~ility: (No~ninal) NaCl ~5t I.acto~;e 0-4~.t M~gne~ a Sul~ate 5~4 ~alciu~ Chloride 70 ~alaium Pho~phate ~-60~ (pH ~ependent~
citri~ AC:id 10-9S~ ~p~I Dependent) Açetic ~cid 10-95~ ~pH Dep~ndent) Molecular W~ ht Rejections:
Re~ectioh al:~ve 500 !1~S%
R~ect:ion Below ~00 S~c Flux Ri~te: 20 l/m~/h no~inal desisp~ f`lux rate 40C
2!1e~bxa.ne size: 4~x 30~ spiral with 6m2 membrane area per ~0 el~ent Operating Pressure: 41 B~x (500 PSIG~ Max.
30-40 Bar ~a50-600 PSXG) r~con~dçd.
Tempexature lîmita~ions: 57C~ lfaximu~, 10-50t~.
2~ rec:omn~ended.
pH~roleranc~e 2~3 mini~num 11.0 ~axl~ ;hort: term exposure 2 ~ 3 to 10. 0 ~sc:om~end~
Oxidi~er tolerance: NON~æ
I'cejection rate: ~9~9~ ~ue Protein Iq~P) Flux r~e: 27 l/~/h ~inal de~ c rate (5 A oo~Ppany Osmonic~ Ina. l~anu~ ture~ an experimental ~e311bran~ de~ nat13d ~Osmo ~X-06" w~ h ~ a ~hin f il~n, m~mbrane ~mllar to th~ Filtratis:~n E:ngineering me~r~nes.
~Iowevex, tl~e ~nanu~acturer hai; not p~blishe~ any speci~ication~
5 on this ~e~brane.
Por ~11 the nano~iltQr ~embrane~, ~e xejection o~
m~qne~;iun~ s3ulPat~s is fairly high (~0-~ pex~ent3, while the rejection oiE sod~ lo~ide i in the 50 percent range or lowe~r. Since ~eæe m~mbrane~ ilre negatively cha~ged, i~ i~
10 the ~nion repulsion which ~uainly determines the solute rejection. For ex~ple, the rejecl;ion of calciuhl ~hl~ride is a~out t:he ~;ame (ceLn even be lower~, ~han ~:hat of ~;odium chlori~e whil~3 r~jectlon of ~ium ~ul~a~e is about th~ C~me as ~ha~ for Pla~3ne~ium sulfate. ~i- and multiv~l~n~ anions are 15 highly reject~3d. so ~a:r, no ~ wn ca~e ha~; evolved where highly a~arged ca~ions have interaated ~ith the nanofiltration ~embranes to give ~ positive n~3t surfaGe charge~
In gen~ral, according to the invention, a 5.~ to 50%
olution of the desired low ~o~eqular w~ight compound or 0 molecule i~ fed to a n~no~ er under approxi~nately 600 PSI.
low ~nole~ular weight has less ~han 500 ~W. The product pas~ throu~h the ~e~brane while varyins~ degreeR of the larqer molecules do not pa~R through and are retained by the memb~ane~ a~ount o~ any given molec:ule pa56in9 through 25 the ~embrane ~pend~3 on the molecular weight, ionia c:harge, an~ corlcentration o~ ~he ~olec:ule ~ n the ~eed str~am~
Durin~ an experimental practi~e of the inv~ntion, dextro~e w~ ret~ined by th~ membran~ in ~ lo~ ~oncen~r tio~;

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however, ~en a ~ dex~rose i8 u~ed, ~ dextro~e permeates to -~o~e ex~ent while virtu~ all o e the higher oligosaccharide~ a~e ~etained.
In thQ ~ase of an org2nic aoid ~alt, 8uch as lactic acid ~ore or le~s o~ the acid ~ppears in ~he permeate tr~a~

depending on w~ether it i6 present a~ salt or ~ a f~ee acid.
The stre~ permeates ~he mem~rane ~aster a the ~r~e acid than it doe8 a~ the sal~.
Pig~ 2 hows a laborat~xy instrument Whi~h ha~ been des~gnated ~O~mo l~TN by its manufacturer. This inqtrument ~a~ u~ed in the laboratory to make experimental runs leading to some o~ the ~ollowing wo~king examples. I~ h~s an open tank 50 ~or holding glucoæe ~yrup 27, the tan~c being coupl~d through a feed pump 5~ and ~ pre~æure pump 54, to a m~m~rane 1~ ~e~sel 56. A pressure gauge 58 ~aintain~ about 450 PS~ at 4-gallons per minute. Suitable valve ~eans 60 passe~ a limi~ed *lo~ which cre~e~ a feed ba~ loop repre~ented by arrow A in order to mix some of the ~eed stre~m which has gone ~hrough the turbulence oi pump 54 bQck into the fresh, incoming ~eed strea~. ~he limited ~low also buffer ~tores ~o~e material to ad~u~t the line pressur~ to the ~S0 PSI.
The me~bran~ vessel 56 ~ay he thought of as a ~a$nle~
~teel tube ~avin~ a membrane ~tretched diametrically acro~
it~ interior to divide the interior into entrance and exi~
chambers wi~h the only passaqe ~e~we~n the~ bein~ via the me~brane. The membrane may be ~hought o~ as a strai~er ~hi~h doe~ not pass any molecule~ which are larger ~han ~ aex~ro~e mole~ule. ~n reali~y, the membrane is a co~plex spiral shape.

2 f3 3 ~

In a~y even~, the material en~e~ vesse~ 56 on ~n entrance si~e o~ the memb~ane, passes through t~e ~e~bran~, and leave~
from an exi~ side, a~ a permeate at 62.
Sin4e ~ r mol~cule~ ny, wer~ removed earlie~ in the process, the permeatc at 62 i~ al~Qst pur~ dextrose.
Therefore, on the entranae ~ide of th~ ~e~brane, ~ater$al which doss no~ pas~ through the ~e~brane build~ up and could accumulate to ¢log th~ ~e~brane. T~ av~id this clog~ing, so~e o~ th~ ~a~erial ~rst~ntate~) i8 returned ~roM tke entrance side, th~ough a pipe 64, to ~he ~nk. ~ pre ~ure gauge 66 is ~et at ab~ut 430 PSI which e~tabli~heæ a net di~fer~nce o~ ~0 PSI acro~ th¢ m~mbrane. The valve ~ iæ set to ~just the vol~e o~ the fed baok retentate.
A pilot ~yste~ (Fig. 3) was set up in a fa¢tory to test lS larger 6cale produ¢tîon. In this ex~mple, the glucose syrup 27 ente~ via a feed pipe 70, p~ed ~hroug~ a pump 72, and flow ~et~r 74 to a ~embrane t~nk ve~sel 76, which is con8tru~te~ approximately ~ha ~a~e as the vecsel 56. A
pressur~ ~auge 78 con~rols the input pressure to the membrane.
~0 A r0~irculation loop lshown by arrow B) h~s a ~low which is contr~lled by valve 80.
The out~lo~ product of the puri~ied ~ex~rose product appe~r~ at 82, A pres~ure g~uge ~4 maintain~ the ~ack pressure on the membrane in AbOU~ ~he s~me ~anner that gauge 6~ maintain8 ~t. Pxe ~ur~ control valve 86 iæ adju~ted ~o m~intain the desired pressure ~eadinq a~ ~auge 84. A portion of the xetentate is ~ecycled at 88 ~o the input o~ pu~p 72.
~nother v~lve 90 i~ set so ~h~t a percent~ge o~ the retentate 2~3~
. . .. . .. . . ..... . . . ..

is bled of~. ~hi~ ~}e~d material ~ay b~ u~ilized in any suit~le ~ann~r, a~ ~y returning t~ som~ appropri~te ups~rea~
point in ~he proce~s of Fig. 1 or ~y U8ing it to produae produc~s other than su~tantially ~re dextrose.
EXAMPL~
Three mem~ranes were test~d for dex~xose puri~ica~ion o~
a ~e~d ~ream derived ~r~ s~ccharifie~ ¢orn starch, U~in~ an Osmo l~T pilot 8y~e~.

Roci~. ~C. Pæ~ p~ p~
Mepl~ Phw ~pm T~np. ~ GP2DpSl ln PS~ Out E~p. M. S~ 3 ~i 3.S 5.fi 370 35 Filmt~cNP-40 S 4G 2.0 2.Z 370 34~
Pilttati~ 0 ~ 45 ~: I 450 410 t4~S) Resul~
Dextro~e Concen~ration g/100 ml %Dextroæe Puri~y ~ Perme~te ~Permea~e EXp~ M~ Serie~ 2g.8 21.3 ~6 9~.7 NF-40 30 23 96.1~9.2 ~ U0 30 19.7 g6.2 3~ æLE_Z

~arger s~le ~Uns wsre c~ried out using a ~ltration En~ineering ~0 me~br~ne. An around th8 clock ~yæ~em ~a se~

Up to deter~ine ~iltxation d~ring a production ~aale 4~

opRrations. ~he ~e~brane had lOOa square feet of filtration are~. The re~ults are ~h~n ~elow:

203~'~5~'~

P~ssureP~I Flow 8pm I~

0700~lo 9~ Io ~ ~.7 o~oo410 ~g 12 0 9~ g 2~
~ao~10 a7s ~ 57 0 Io 2.6 14~
2n ~ g.7 2~0n~10 ~ n ~soO410 s7~ ~19 ~ 2~ .7 om~~10 39~ ~1 9 0600~10 ~ 19R9g.6 n~ o 978 la~ 9 15 Th~3 daily ~verage re~ult~ i~or t~e pxoduct and feed proper1:;ies a~e shown below~
Dry ~ lid~ Dextrc~se Pu~ y Feed 27.. 2 ~6.8 2 0 Product 1~ . ~ 9~ . 7 E~le~d~ 28~ 7 96. 0 * When ~he mem~r~e pas~es ~ ain mater~al and blocks other ~aterîal, ~he bloclced mate~ial builds up a concentrated solution on one side of the m~brane. A
~ tain peraen~aqe o~ t~is aoncentrated ~olution must be withdrawn ~sfor~ ~he conc~3ntr~tion becomes exc:e~sive.
drawn of~ material i~; called "bleed".

Tw~nty qallon lbatches of dextrose li~or having different 3 o percesn~ages o~ dry solid~; ~er~3 proce~;~;ed in an O:;mo l~T pilot s3y~tem~ u;~in~ a Filrate¢h NF~o me~brane. The proc:es~
conditions, ~l~xe~: and purity o~ l~eed and product ctreams a~e f;hown beluw .

2 ~
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2~3~

Dry Solid~ ~ex~roæe Purity W/T~ _ ~
Fead~B.4 g6~2 Product2~1 9~6 Bleed30~5 95.1 FX~MPL~ 5 A con~entrated 50~,000 M~ ultra~iltered Lactobacillus ca~ei fe~mentation ~r~th which cont~lned approximately 36 la~tate ion w~ dilute~ to appr~xim~tely 1~ lactate, ultrafiltered (50,000 in~ert, ~W) and n2n~iltere~ at pH ~.0 and at pH ~3 aPter p~ adju~tment with sul~ric acid. The fermenta~ion bro~h used in this Exa~ple 5 was taken ~r~m a 48-hour ~ermentakion of a solu~ion oont~ni~g 140 grams 4~
dextrose per liter, 5 gramsJliter o~ ~eaat extract~ 30 gra~s steepwater dry ~olids/liter, and 1.0 gra~ of (N~)2PO4 per liter. This m~sh was ~rmented With Lactobacilluc çasRi su~species rhamnocus with a~monia added ~or p~ control at p~
6.0 and 110C. Wh~n all of the de~tro~e was fermen~edr the br~th was ultra~ ered an~ con~entrated ~o 36% lacta~e ion~
~0 For this ex~ple, testing was condu~ted on an Osmo l9T
pilot s~em wi~h ~n Osmo MX06 me~brane a~ ~ppr~Yimately 400 PSI and 45 c~ Sample~ of the 41tra~iltered material (A), nano~i~t~red at p~ 6 (B), an~ nanofiltered a~ pH 2.3 (~) were a~l ad~usted to p~ and ~oncentrated to between ~0-3~
lactic a~ld ~or ~urther processing. An HPL~ ~high pressure liquid chromatography~ analysis wa~ c~rried out on these s~mples wl~ the results which are shown belowc ~g'~

L~k~ r~ry ~lids ~I)P~ ~
San~le al~:~ % DP_ ~1Lqctio Acid A 34 2.~ 60 B 34 0.1~ Q~6 6 ~ 2~ 0.08 0.5 6 DP31 ~ ~ri~accharide~ ~nd high~r pol~mers.
DP2 = Disac~harid~s DPl - Nonosaccharides As can be seen t~e nano~ilter removed ~o~t of the ~i ~ccharide~ and some ~f the ~ono~acchar~de8. Also, at pH' 5 where the lac~ic acid ~ not ionized, the ratio o~ lactic ~cid to inorgani~ Qalts in the pe~eate increa~ed, thereby pro~idinq a higher puri~ication factorO
lS Those who are skilled in the art wi~l readily percei~e how to ~odi~y the inven~ion. There~ore, the appe~ded claims a~e to ~e construed to ~over all equi~lent ~tructures which fall within the true ~aope and spiri~ o~ th~ învention.

Claims

The claimed invention is:
(1) A process for making high purity dextrose, said process comprising the steps of:
(a) forming corn starch slurry;
(b) cooking said starch slurry in presence of .alpha.-amylase for a period of time which is long enough to produce gelatinization and dextrinization;
(c) treating the dextrinized product of step (c) with a glucoamylase enzyme at - 60°C to produce a saccharification, and a resulting glucose syrup; and (d) nanofiltering said glucose syrup to produce a high purity dextrose.
(2) The process of claim 1 wherein said nanofiltering of step (e) comprises the step of passing said glucose syrup through a membrane having a pore size which passes dextrose molecules while rejecting di- and trisaccharides molecules of glucose.
(3) The process of claim 1 wherein said nanofiltration of step (e) includes the added step of passings said glucose syrup through a nanofilter membrane at approximately a pressure in the order of about 400-425 PSI, and at a temperature in the range of about 120°F to about 145°F.
(4) The process of claim 1 wherein said nanofiltration of step (e) includes the added step of passings aid glucose syrup through a nanofilter membrane which passes solution having a dextrose purity in substantially the range of about 96-99.7%.

(5) The process of claim 1 wherein said nanofiltration of step (e) includes the added step of passing said glucose syrup through a nanofilter membrane which passes a solution having dextrose purity is at least 99%.
(6) The process wherein the pH of organic acid solutions to be purified is at or below the pK of said acid.
(7) The process of claim 6 and the added step of carrying out said nanofiltering 1 pH unit below its pK.
(8) The process of claim 6 and the added step of adjusting the pH of the nanofiltered material to be substantially in the range of about 2.3 to 2.4.
(9) The process of claim 6 and the added steps of providing an ultrafiltered Latobacillus casei fermentiation broth of approximately 10% lactate, and nanofiltering the diluted lactate ion.
(10) A process for purifying a material containing a glucose syrup mixture of dextrose and di- and trisaccharides, said process comprising the step of nanofiltering said mixture through a nanofiltration membrane made of a cross-linked polyamide, having approximately the following characteristics:
Within the range of:
Pressure to product about 4-20 43?/m2/h permeate flux, bar operating pH range 2-10 max. Temp. °C 45 approximate solute rejection%
NaCl 40-70 MgSO4 90-98 Glucose 90-98 Sucrose 98-99 (11) A process for purifying material containing a glucose syrup mixture of dextrose and di- and trisaccharides, said process comprising the step of nanofiltering said mixture through a nanofiltration membrane made of a cross-linked polyamide, having approximately the following characteristics for passing molecules in the sizes of:
Molecule About NaCl 95%
Lactose 0-4%
MgSO4 5%
Calcium Chloride 70%
Calcium Phosphate 20-60%
Citric Acid 10-95%
Acetic Acid 10-95%
(12) The process of claim 10 wherein said membrane rejects about 95% of molecules having a molecular weight of at least 500.
(13) The process of claim 10 wherein said membrane rejects about 5% of molecules having a molecular weight of not over 200.
(14) A system for processing a feed stream comprising a fluid carrier and solid material at least some of which is in the MW range of dextrose, said system comprising a vessel having a nanofiltering membrane dividing said vessel into an entrance side and an exit side with passage between said sides within said vessel being exclusively through said membrane, said membrane having pores which pass molecules up to and reject molecules which are larger than substantially the size of a dextrose molecule, means for conveying said feed stream through said vessel with a predetermined pressure differential between said entrance and exit sides, recycle means for feeding back some of the material in said entrance side to a point in said conveying means which is upstream of said vessel, and means for bleeding off some of said material in said entrance side.
(15) The system of claim 14 wherein said pressure differential is approximately 20 pounds per square inch.
(16) The system of claim 124 wherein said nanofiltering membrane includes the added step of passing said glucose syrup through a nanofilter membrane which passes a solution having dextrose purity in substantially the range of about 96-99.7%.
(17) The system of claim 14 wherein the feed stream is glucose syrup and the nanofiltering membrane passes dry solids having a dextrose purity of a to least 99%.
(18) The system of claim 14 wherein the pH of organic acid solutions is at or below the pK of the organic acid.
(19) The system of claim 14 wherein said nanofiltering membrane is made of a cross-linked polyamide, having approximately the following characteristics:
Within the range of:
Pressure to product about 4-20 43?/m2/h permeate flux, bar operating pH range 2-10 max. Temp. °C 45 approximate solute rejection%
NaCl 40-70 MgSO4 90-98 Glucose 90-98 Sucrose 98-99 (20) The system of claim 14 wherein said nanofiltering membrane is made of a cross-linked polyamide, having approximately the following characteristics for passing molecules in the sizes of:
Molecule About NaCl 95%
Lactose 0-4%
MgSO4 5%
Calcium Chloride 70%
Calcium Phosphate 20-60%
Citric Acid 10-95%
Acetic Acid 10-95%
(21) The system of claim 14 wherein said nanofiltering membrane rejects about 95% of molecules having a molecular weight of at least 500.
(22) The system of claim 14 wherein said membrane rejects about 5% of molecules having a molecular weight of not over 200.