Acid Citric-Acid Lactic

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Hnh 1: Cu to ca acid citric C6H8O7

1. GII THIU V LCH S PHT TRIN: Forter m u quyn sch Hot ng ha hc ca nm bng mt tuyn b: C l cc nghin cu tp trung vo qu trnh ln men acid citric cn nhiu hn c nhng nghin cu v cc chc nng khc trong qu trnh bin dng nm mc, tuy vy, nhng kin thc c bn c quan tm n c l t hn c nhng qui trnh c miu t trong quyn sch ny tuy nhin nu xt trong lch s nghin cu, ln men acid citric l qui trnh v nm u tin c tim nng trong cng nghip c khm ph. Thc vy, t khi iu ny c cng b th s lng cc bi bo v ch ny tng ln ng k v hi vng rng n s gp phn xng ng vo khi kin thc v cng ngh v sinh ha vi sinh vt. Nm 1891- 1893, ln u tin s to thnh acid citric c quan st thy bi Wehmer, n c xem nh l mt sn phm ph trong qu trnh sn xut acid oxalic bng cch nui cy Penicillium glaucum trn mi trng c ng. Nm 1893, ng phn lp c hai chng mi c kh nng tch ly acid citric v cho rng chng l mt chi mi. Cytromyces c xem nh l chng Penicillia n vng (Wehmer, 1903). Nhng th nghim ca Fabrique de Produit Chimiques de Thann et the Mulhouse nhm sn xut to acid citric trn quy m cng nghip b tht bi. Nguyn nhn dn n tht bi l do qu trnh ln men phi c tin hnh trong vi tun th mi thu c mt sn lng ng k v vy rt d b tp nhim. c bit l v Wehmer tin vo nhng tuyn b mang tnh thuyt phc ti thi im rng to ra v duy tr sn phm acid th acid to thnh phi c trung ha.

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Nm 1913, Zanhorsky c cp patent (bng sng ch c bng quyn) cho quy trnh sn xut acid citric khi s dng Sterigmatocytis nigra mt tn gi khc ca cho Aspergillus niger. Tuy nhin chnh kt qu nghin cu ca Currie mi m ra con ng cho nhng thnh cng sau ny ca vic sn xut acid citric quy m cng nghip. Nm 1916, J.N. Currie vi vai tr l cng s ca tin s Ch. Thom - ngi ng u phng th nghim vi sinh Cc Ha Hc ti thnh ph Washington.DC, ln u tin quan st thy mt s lng ln cc chng Aspergillus niger c trong phng th nghim c kh nng sn xut mt lng ng k acid citric trong nhng iu kin thun li. Pht hin c cho l quan trng bc nht chnh l Aspergillus niger pht trin rt tt khi gi tr pH nm trong khong t 2,5 3,5 m acid citric li c to ra nhiu khi gi tr pH ca mi trng mc thp. Hn th na, im ni bt ca pht hin ny chnh l vi gi tr pH thp nh vy th sau t 1-2 tun c th thu c gn 60% sn lng trn mi trng ti thiu vi kh nng b tp nhim l rt thp. Cho n lc ny, tng lng dung dch acid citric c to ra t nc p tri cy (ch yu l t chanh) khong 10.000 t/a, trong hm lng acid citric nguyn cht chim 7-9% v tn ti di dng mui calcium. sn xut ra 1 tn acid citric cn khong 20 - 30 tn chanh (tng ng vi din tch khong 2,7 ha). Lc ny, Italy l nc cung cp hn 80% nhu cu v acid lactic ca th gii. Nhiu cng ty cc nc khc nhau tin hnh nhp t mui calcium citrate n acid citric ch yu l cung cp cho ngnh cng nghip sn xut thc ung. Sau khi kt thc chin tranh th gii th nht c nc xut khu l Italy ln cc nc nhp khu u ri vo hon cnh ti chnh kinh t b hn ch, v vy hnh thc sn xut c khng cn ph hp, ngi ta tin hnh tm kim nhng phng thc sn xut acid citric mi. Chnh lc ny, nhng pht hin trc y ca Currie mi tr thnh nhng cng c quan trng nht cho s pht trin ca ngnh cng nghip sn xut acid citric trn quy m ln bng hnh thc ln men. Vic Currie pht hin ra rng Aspergillus niger c th pht trin v tch ly acid citric ti pH < 2 cho ngha l khi qu trnh ln men c bt u nng pH ny th kh nng ca s xm nhim c th c loi b hon ton. Hn na, ng tm ra rng nng ng cao l iu kin thun li nht cho t l sn phm cao v ng quan st thy rng sn lng ti u ch c th t c di iu kin gii hn pht trin. Nm 1919, nhng n lc khc nhm a hnh thc ln men acid citric vo trong sn xut thng mi b tht bi (Societ des Produits Oganiques de Tirlemont, B), nhng n nm 1923, Chas. Pfizer & cng ty ti New York, thnh cng khi p dng phng php ca Currie v h tr thnh nhng ngi sn xut acid citric ln nht th gii. Sau , ti Anh, J v E. Sturge tin hnh sn xut calci citrate theo quy trnh theo quy trnh tng t da trn bn quyn sng ch ca Fernbach v cs. (1927- 1932). Nm 1928, mt nh my sn xut acid citric da trn ngun carbon r tin l mt ng c ci c xy dng ti Kaznjov gn Plzen, Cng ha Czech (Montan - und Industrialwerke, vorm. J.D. Stark, 1924; Szucs, 1925). Kh khn khi s dng loi vt liu ny chnh l s hin din ca cc ion kim loi, trong ng vai tr quyt nh l cc ion kim loi chuyn i. Theo Leopold v Valtr (1964) th cc nh my ny cn s dng hexacyanoferrate (HCF) trong bc u tin ta hoc to phc hp vi cc kim loi khng mong mun trong mi trng. iu ny c ct gi b mt v c cng b kh tr vo nm 1938 vi bng sng ch c cp cho Mezzadroli (1938).

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Nhiu nh my c xy dng ngay sau nhiu nc nh l Lin bang Soviet, c (Joh. A. Benekiser GmbH), B (La Citrique Belge) v mt vi nc khc. K t nm 1933 theo Perquin (1938) tng lng acid citric trn th gii l 10.400 tn vi ch 1.800 tn c sn xut t Italy, phn cn li c sn xut vi quy m ln bng cng ngh ln men ( Chu u: 5.100 tn, M: 3.500 tn). Rt nhiu tc gi tham gia nghin cu gip lm sng t c ch sinh ha ca qu trnh sn xut acid citric nh l Bernhauer (1940), Foster (1949), Prescott v Dunn (1959) hay Johnson (1954). Mt cu hi kh th v c t ra: c bao nhiu gi thuyt c a ra cho ti khi con ng sinh tng hp acid citric t con ng ph v carbohydrate thng thng c cng b v phn ng nn tng ca chu trnh tricarboxylic acid (TCA) s tch t acetyl CoA v oxaloacetate, c hiu mt cch r rng. Tuy nhin, c ch iu ha dn n s tng hp acid citric vi hm lng cao v s bi tit nhanh chng ch mi c bt u nghin cu t thp nin 1970 v n tip tc c nhiu nhm nghin cu quan tm. Ban u vic ln men acid citric c tin hnh theo hnh thc nui cy trn b mt. Sau ny hnh thc ln men chm c ngh tuy nhin hnh thc ny cn ny sinh nhiu vn ch yu l do iu kin ca h thng ln men v c bit chng sn xut nhy cm vi nhiu yu t m cho n nay vn cha c nhn thc r. Tc ng ca cc ion kim loi chuyn i c cng b nhiu hn v iu l cn thit la chn cc loi vt liu th ph hp. Trong sut thp nin 1950 t l ca cc phc cht c bn trong qu trnh ln men c tuyn b. Ch vi hnh thc ln men ny m c rt nhiu chin lc c bit c pht trin tng ng vi cc loi vt liu th. Nm 1944, Szucs a quy trnh hot ng chia thnh 2 giai on chnh: giai on u kch thch s pht trin ca h nm si, giai on sau gii hn s pht trin to acid citric. t c iu ny cn cung cp mt lng phospho (~ 70mg/l) vo trong mi trng giai on pht trin v chun b mt lng phospho t do trong mi trng giai on sn xut sn phm. Nm 1948 - 1949, Shu v Johnson ci tin mi trng ln men c th tin hnh c hai giai on trong cng mt h thng. Cc tc gi ny ch ra rng iu kin ti u ca qu trnh ln men i hi phi c s cn bng gia mangan, km, phospho. Trong ln men thng mi vic b sung cc nhn t cn thit l rt kh khn v quy trnh ny s dng cc vt liu th c thnh phn khng c xc nh r rng (v d mt r ng). Rt nhiu cng trnh nghin cu c thc hin tm kim iu kin ti u khi s dng cc loi c cht r tin nh l mt r ng (Shu, 1947; Karow v Waskman, 1947; Woodward v cs., 1949; Moyer, 1953), tinh bt (Moyer, 1953a, b), tinh bt c thy phn (Schweiger v Snell, 1949). C rt nhiu quy trnh x l v tinh sch mt ng c bit l vic loi b cc kim loi vt. Hu ht chng u c x l bng HCF u tin, hin nay ngi ta ngh vic s dng cc ht trao i ion (Perlman v cs.,1945 Woodward v cs.,1949 .). Tuy nhin hu ht cc th nghim ch ra rng HCF va ng vai tr l cht loi b ion, va ng vai tr l cht ng c ch s pht trin c th tch t c nhiu acid . Mt bc t ph chnh t c ti M bi nhng ngi ngi nghin cu ca tp on Miles Laboratories. Trong qu trnh pht trin k thut cc tc gi gii thiu phng php s dng tinh bt c thy phn nh l mt loi c cht r tin. Khi nghin cu vi nhng vt liu th tinh khit hn, h pht hin ra rng hot ng bt li ca cc kim loi vt, c th b bt hot nu thm vo mt lng va ion ng

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(Schweiger 1959,1961). Hn th na, tng t HCF, nu ion ng c thm vo vt qu mt lng nh th s rt thun li cho vic sn xut acid vi sn lng cao. Hon cnh hin ti: nhiu cng ty s dung nhng thnh tu k thut ca ln men chm v sn xut khong 80% lng acid citric trn th gii. Ch mt vi cng ty vn cn tip tc s dng phng php nui cy b mt truyn thng .

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Hnh 2: Con ng chuyn ho n gin trong sn xut acid citric t carbohydrate v n-alkan

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Vo thp nin 1960 mt quy trnh mi c ra trong khi nghin cu m rng trn vic s dng n-alkan nh l mt ngun carbon cho qu trnh sn xut sinh khi vi sinh vt (protein n bo, SCP) v nhng sn phm khc nh acid amino, vitamin, acid hu c .v.v. Cc nh nghin cu ti Nht Bn l nhng ngi u tin s dng cc chng vi khun Corynephom t bin thay cho Corinebaterium, Arthobater v Brevibacterium trong cng ngh ln men ngay sau tr thnh mt cng ngh c thit lp vi nhng c tnh tiu biu ca nhng thnh tu tr tu. Nm 1966 - 1967 mt vi chng t bin c to ra sn xut acid citric t n-parafins (C9-C30 )v cc c cht lin quan. Mc d n c ng k bn quyn (Tanaka v cs., 1968), tuy nhin n khng c khai thc trn quy m cng nghip. Sau ngi ta pht hin ra rng nm men, chng Candida v cc dng lin quan s dng n-alkan lm ngun carbon cho ngun sn xut sinh khi ng thi n cng c th sn xut ra mt lng ln acid citric t nparafins sn phm c trn ln (isocitric acid) (Fukui v Tanaka,1980). Nhng n lc c lp acid citric nh l mt sn phm ph trong qu trnh sn xut SCP sm c thay th bng vic u t nghin cu sn xut acid citric nh l mt sn phm chnh. iu ny cng do vic sn xut SCP t ngun hydrocarbon khng c chp nhn v nhng nh hng ca n n sc khe vt nui. Mc d sn lng acid citric to ra t cc alkan t C9 C20 trong phng th nghim t hiu sut 100% nhng vic a vo sn xut cng nghip vn b hn ch bi mt vi l do: vic sn xut acid citric t c cht ny lun km theo mt lng ln isocitric acid m s c ca cht ny khng c chp nhn trong nhiu ng dng, v d trong sn xut thc n cng nghip; vic chn dng v xc nh cc thng s ti u ca qu trnh cn c xem xt. Trong thi gian ch i th r rng n khng phi l mt c cht r to ra sn phm cui cng l acid citric. Cho d nh th no th vic nghin cu li ng dng ca nm men hoc vi khun cng em li nhiu hiu qu th v. c bit trong thi k ca vic sn xut acid citric nh l mt sn phm ph ca sn xut SCP. Vic ny cn thit thc y cc quy trnh c lp dung dch acid citric. Phng php li trch bng dung mi c pht trin v ngy nay c ng dng ph bin trong hot ng ln men truyn thng. Mt khc, ngi ta cng quan st thy rng c nhng chng nm men c th sn xut c acid citric khi pht trin trn mi trng c cha glucose hay cc ngun carbon tng t (Tabuchi v cs., 1969; Abe v cs., 1970). Nhng kt qu tm ra c nghin cu m rng v pht trin xa hn trong nc CHDC c. Nhng lin kt vi ngi c c l hn ch cc