Gluconic acid

ORGANIC ACID PRODUCTION

1. GLUCONIC ACIDS
Dr. Esther ShobaR
Assistant Professor
KristuJayantiCollege
Bangalore

2. INTRODUCTION
•Gluconicacid(pentahydroxycaproicacid),isproducedfromglucose
throughasimpledehydrogenationreactioncatalysedbyglucose
oxidase.
•
•OxidationofthealdehydegroupontheC-1ofᵝ-D-glucosetoacar-
boxylgroupresultsintheproductionofglucono-d-lac-tone
(C6H10O6,)andhydrogenperoxide.
•Glucono-d-lactoneisfurtherhydrolysedtogluconicacideither
spontaneouslyorbylactonehydrolysingenzyme,whilehydrogen
peroxideisdecomposedtowaterandoxygenbyperoxidase

3. •Theconversionprocesscouldbepurelychemicaltoo,butthemost
commonlyinvolvedmethodisthefermentationprocess.
•Theenzymaticprocesscouldalsobeconducted,wherethe
conversiontakesplaceintheabsenceofcellswithglucoseoxidase
andcatalasederivedfromA.niger.
•Nearly100%oftheglucoseisconvertedtoglu-conicacidunderthe
appropriateconditions.ThismethodisanFDAapprovedprocess.

5. HISTORY
•Gluconicacidproductiondatesbackto1870whenHlasiwetzand
Habermanndiscoveredgluconicacid
•In1880Boutrouxfoundforthefirsttimethataceticacidbacteria
arecapableofproducingsugaracid.
•In1922MolliarddetectedgluconicacidintheSterigmatocystis
nigra,nowknownasAspergillusniger.
•Later,productionofgluconicacidwasdemonstratedinbacterial
speciessuchasPseudomonas,Gluconobacter,Acetobacter,and
variousfungalspecies.

6. PROPERTIES
•Gluconicacidisanoncorrosive,nonvolatile,nontoxic,mildorganicacid.
•Itimpartsarefreshingsourtasteinmanyfooditemssuchaswine,fruitjuices,
etc.Sodiumgluconatehasahighsequesteringpower.
•ItisagoodchelatoratalkalinepH;itsactioniscomparativelybetterthanEDTA,
NTAandotherchelators.
•Aqueoussolutionsofsodiumgluconateareresistanttooxidationandreductionat
hightemperatures.
•Itisanefficientplasticizerandahighlyefficientsetretarder.
•Itiseasilybiodegradable(98%at48h).
•Ithasaninterestingpropertyofinhibitingbitternessinfoodstuffs.
•Concentratedgluconicacidsolutioncontainscertainlactonestructures(neutral
cyclicester)showingantisepticproperty.
•

7. •In the European Parliament and Council Directive No. 95/2/EC,
gluconicacid is listed as a generally per-mitted food additive (E
574).
•The US FDA (Food and Drug Administration) has assigned sodium
gluconate a GRAS (generally recognized as safe) status and its use
in foodstuff is permitted without limitation.

8. APPLICATIONS
•Generallyspeaking,gluconicacidanditssaltsareusedinthe
formulationoffood,pharmaceuticalandhygienicproducts
•Gluconicacidisamildorganicacid,whichfindsap-plicationsinthe
foodindustry.
•Asstatedabove,itisanaturalconstituentinfruitjuicesandhoney
andisusedinthepicklingoffoods.
•Itsinnerester,glucono-d-lactoneimpartsaninitiallysweettaste
whichlaterbecomesslightlyacidic.
•Itisusedinmeatanddairyproducts,particularlyinbakedgoodsasa
componentofleaveningagentforpreleavenedproducts.
•Itisusedasaflavouringagent(forexample,insherbets)anditalso
findsapplicationinreducingfatabsorptionindoughnuts

9. •Differentsaltsofgluconicacidfindvariousapplicationsbasedon
theirproperties.
•Sodiumsaltofgluconicacidhastheoutstandingpropertytochelate
calciumandotherdi-andtrivalentmetalions.
•Itisusedinthebottlewashingpreparations,whereithelpsinthe
preventionofscaleformationanditsremovalfromglass.
•Itiswellsuitedforremovingcalcareousdepositsfrommetalsand
othersurfaces,includingmilkorbeerscaleongalvanisedironor
stainlesssteel.
•ItspropertyofsequesteringironoverawiderangeofpHis
exploitedinthetextileindustry,whereitpreventsthedepositionof
ironandfordesizingpolyesterandpolyamidefabrics.
•

10. •Itisalsousedinmetallurgyforalkalinederusting,aswellasinthe
washingofpaintedwallsandremovalofmetalcarbonate
precipitateswith-outcausingcorrosion.
•Italsofindsapplicationasanadditivetocement,controllingthe
settingtimeandin-creasingthestrengthandwaterresistanceofthe
cement.
•Ithelpsinthemanufactureoffrostandcrackresistantconcretes.
•Itisalsousedinthehouseholdcleaningcom-poundssuchas
mouthwashes.

11. •Calciumgluconateisusedinpharmaceuticalindustryasasourceof
calciumfortreatingcalciumdeficiencybyoralorintravenous
administration.
•Italsofindsaplaceinanimalnutrition.
•Irongluconateandironphosphogluconateareusedinirontherapy.
•Zincgluconateisusedasaningredientfortreatingcommoncold,
woundhealingandvariousdiseasescausedbyzincdeficienciessuch
asdelayedsexualmaturation,mentallethargy,skinchanges,and
susceptibilitytoinfections.

12. PRODUCTION
•Therearedifferentapproachesavailablefortheproductionofgluconic
acid,namely,chemical,electrochemical,biochemicaland
bioelectrochemical.
•Amongvariousmicrobialfermen-tationprocesses,themethod
utilisingthefungusA.nigerisoneofthemostwidelyusedones.
•However,theprocessusingG.oxydanshasalsogainedsignificant
importance.
•Irrespectiveoftheuseoffungiorbacteria,theimportancelieson
theproductwhichisproduced,forexample,sodiumgluconateor
calciumgluconate,etc.

13. Gluconicacid production by filamentous fungi
•4 ENZYMES
•A.nigerproducesalltheenzymesrequiredfortheconversionof
glucoseintogluconicacid,whichincludeglucoseoxidase,catalase,
lactonaseandmutarotase
•Althoughcrystallineglucosemonohydrate,whichisinthealphaform,
isconvertedspontaneouslyintobetaforminthesolution,A.niger
producestheenzymemutarotase,whichservestoacceleratethe
reaction.
•Duringtheprocessofglucoseconversion,glucoseoxidasepresentin
A.nigerundergoesself-reductionbytheremovaloftwohydrogens.
•Thereducedformoftheenzymeisfurtheroxidisedbythemolecular
oxygen,whichresultsintheformationofhydrogenperoxide,aby-
productinthereaction.

14. Gluconicacid production by filamentous fungi
•4 ENZYMES
•Glucooxidase: The reaction involving the conversion of glucose to
gluconic acid by filamentous fungi is catalysed by the enzyme glucose
oxidase
•Glucose oxidase is a flavoprotein which contains one very tightly but
noncovalently bound FAD cofactor per monomer and is a homodimer
with a molecular mass of 130–320 kDa depending on the extent of
glycosylation.
•It catalyses the reaction where glucose is dehydrated to glucono-d-
lactone, while hydrogen is transferred to FAD.
•The resulting FADH2 is regenerated toFAD by transmission of the
hydrogen to oxygen to formhydrogen peroxide

16. •A.nigerproducescatalasewhichactsonhy-drogenperoxide
releasingwaterandoxygen.
•Hydrolysisofglucono-d-lactonetogluconicacidisfacilitatedby
lactonase.
•Thereactioncanbecarriedoutspontaneouslyasthecleavageof
lactoneoccursrapidlyatpHnearneutral,whicharebroughtabout
bytheadditionofcalciumcarbonate,orsodiumhydroxide.
•Removaloflactonefromthemediumisrecommendedasits
accumulationinthemediahasanegativeeffectontherateof
glucoseoxidationandtheproductionofgluconicacidanditssalt.
•Therearereportsstatingthattheenzymegluconolactonaseisalso
presentinA.niger,whichincreasestherateofconversionof
glucono-d-lactonetogluconicacid

17. MEDIA AND PHYSICAL PARAMETERS
•Glucose at concentrations between 110–250 g/L
•Nitrogen and phosphorus sources at a very low concentration (20
mM)
•pH value of medium around 4.5 to 6.5
•Very high aeration rate by the application of elevated air pressure
(4 bar).

18. RAW MATERIALS
•Glucose is generally used as carbon source for mi-crobial
production of gluconic acid.
•However, hydroly-sates of various raw materials such as agro-
industrial waste have also been used as substrate.
•Kundu and Das obtained a high yield of gluconic acid in media con-
taining glucose or starch hydrolysate as the sole carbon source.
•Vassilev et al.used hydrol (corn starch hy-drolysate) as the
fermentable sugar to produce gluconic acid by immobilized A. niger.
•Rao and Panda used Indian cane molasses as a source of glucose.

19. SSF and SUBMERGED FERMENTATION
•SSFhasbeenwidelydescribedfortheproductionofindustrial
enzymesandorganicacids.
•However,fortheproductionofgluconicacid,thereareonlyafew
reportsusingSSF.
•.AstudybyMoksiaetal.usedatwo--stepprocess,thefirstbeing
theproductionofsporesofA.nigerbySSFonbuckwheatseeds,
andthesecondstep,thebioconversionofglucosetogluconic
acidbythesporesrecoveredfromtheSSFmedium.
•Thesporesactedasabiocatalyst,producing200g/Lofgluconicacid
withayieldof1.06gpermassofglucose,veryclosetothe
stoichiometricvalue.

20. PRODUCTION BY BACTERIA
•AceticacidbacteriaandPseudomonassavastanoiwerethecultures
initiallyobservedtoproducegluconicacid.
•Unlikeinfungi,inbacteriathereactioniscarriedoutbyglucose
dehydrogenase(GDH,E.C.1.1.99.17)thatoxi-disesglucoseto
gluconicacid,whichisfurtheroxidisedto2-ketogluconateby
gluconicaciddehydrogenase(GADH).
•Thefinaloxidationstepto2,5-diketogluconicacid(DKG)is
mediatedby2-ketogluconatedehydroge-nase(KGDH).

22. •Allthreeenzymesarelocalisedinthemembranesofthecellsand
areinducedbyhighglucoseconcentrations(>15mM)
•Whentheglucoseconcentrationinthemediumisgreaterthan15
mM,pentosephosphatepath-wayisrepressedandthusgluconic
acidaccumulationtakesplace.
•

23. RECOVERY
•Forobtainingcalciumgluconateasaproduct,calciumhydroxideor
calciumcarbonateisusedastheneutralisingagent.
•Theyareaddedtothenutritivebrothaccompaniedbyheatingand
vigorousstirring.
•Thebrothisconcentratedtoahotsupersaturatedsolutionofcal-
ciumgluconate,followedbycoolingat20°C,andaddingwater
misciblesolvents,whichcrystallisesthecom-pound.
•Atreatmentwithactivatedcarbonfacilitatesthecrystallisation
process.
•Finallytheyarecentrifuged,washedseveraltimesanddriedat80°C

24. RECOVERY
•Fortherecoveryoffreegluconicacidfromcalciumgluconatethe
brothisclarified,decolorized,concen-tratedandexposedto–10
°Cinthepresenceorabsenceofalcohol.
•Thusthecalciumsaltofgluconicacidcrystal-lizes,thenitis
recoveredandfurtherpurified.
•Gluconicacidcanalsobeobtainedbyprecipitatingthecalcium
gluconatefromhypersaturatedsolutionsinthecoldandreleased
subsequentlybyaddingsulphuricacidstoichio-metrically,removing
thecalciumascalciumsulphate.
•Anothermethodofpassingthesolutionthroughacolumncontaining
astrongcationexchangerisalsopractisedwherethecalciumions
areabsorbed.