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Developing Sustainability Technology For Chemical Process Industry: Lactic Acid by Membrane-

integrated Hybrid Process

P. Pal, P. Dey

Abstract- Chemical process industries around the world are desperately seeking for sustainable technology in the backdrop of ever-increasing world population, demand for more employment, industrialization and concern for environment. Process intensification is one such way towards sustainability. The paper focuses on development of a membrane-integrated production system for monomer grade lactic acid with the advantages like, involvement of less processing steps, less energy consumption and less chemical requirement that make the system simple, flexible, compact and environmentally benign. The particular modular design offers great flexibility in operation of the system which the modern manufacturing sector is demanding in this era of emaciated profit margin. The continuous production system offered a reasonably high flux of 76-77 L/ m-2 h-1 of greater than 95% pure L (+) lactic acid.

Keywords---Lactic acid, Membrane Technology, Sustainable Development, Fermentation

I. INTRODUCTION

NTEREST in the production of monomer grade L (+) lactic acid has dramatically gone up in the recent past following a

growing demand for biodegradable polymer (PLA i.e. Poly Lactic Acid), a highly suitable substitute for conventional plastic material. Some major advantages like good heat deflection, ready biodegradability in the environment and sustainability makes PLA even a much better substitute for the petrochemical plastics [1] – [2]. Considering its environment-friendly, thermal, mechanical and chemical nature, PLA can be applied in a wide variety of fields like tissue engineering, controlled drug delivery or in artificial prostheses [3]. Traditional chemical synthesis process for lactic acid

production from petroleum resources yields a racemic mixture of D and L-lactic acids instead of pure D or L lactic acid. Conventional fermentation based processes can be suitably modified and operated with selected microbial strain so as to produce only the desired isomer. But existing fermentation-based processes are still in many cases, only batch processes with poor productivity and necessitating quite a number of downstream processing steps which involve not only high energy, equipment, time and labour costs but also harsh chemicals leading to environmental pollution. Thus process intensification in fermentation based lactic acid production is a demand of the industry drawing attention of the researchers across the world. Process Intensification refers to the development of smaller, cleaner, energy efficient and highly flexible technologies to achieve the same and even more production objectives in a compact plant in comparison with traditionally robust process plants. Conventional production processes produce salts of lactic acid instead of direct lactic acid as pH adjustment is a must by addition of alkalis in such batch conventional processes. This adds a an additional 50% cost on account of chemicals as well as additional separation and purification steps separation and purification steps. Such a conventional process dumps large quantity of calcium sulphate as solid waste, produced through the addition of lime and sulphuric acid [4].Through process intensification, future process industries (chemical and pharmaceutical ) must be capable of providing higher production with reduced energy, raw material consumption and reduced waste generation. Through the concept of

Environment & Membrane Technology Laboratory, Department of Chemical Engineering, National Institute of Technology, Durgapur, West Bengal-713209, India *Corresponding author: Prof.(Dr.) P.Pal : phone: +91 9434469750(Mobile); fax: +91 3432547375; e-mail: [email protected]

developing radical technologies for the miniaturization of process plants, future industries will stand up with reduced

equipment size as well as plant size with increasing inherent safety. Process intensification is kind of revolutionary approach that has the potential of fostering sustainable growth in chemical and allied process industries. Process intensification will eventually replace old, inefficient plants with new and intensified equipment opening up new opportunities for wide variety of patentable products and processes with scale up potentials [5]. Smaller is safer! Hence, process intensification dramatically increases the intrinsic safety of chemical processes. Hybrid reactor system fabricated with the suitable combination of cross-flow flat sheet membrane modules with bioreactor system comes up with the achievement of process intensification by performing multiple tasks in a single and compact unit. Fermentation route for L(+)

I

International Journal of Biological, Ecological and Environmental Sciences (IJBEES) Vol. 1, No. 2, March 2012 ISSN 2277 – 4394

35

lacsughigprofermuwhto andmein thapromeprosepalte

A

fer

ctic acid progarcane juice gh acceptance oduce opticallrmentation prouch more econhich suffers larend product ind shut-down prembranes for thpermeate site

an the RO (revocess intensifiembrane reactooductivity, separating other ernative to the

II. MA

A. Microorgan

Lactobacilrmentative L (+

duction frowith suitable compared to

y pure L(+) ocess with menomically advrgely from lownhibition and rocedures [8]-he separation ois turned out tverse osmosiscation throughor system by lectivity to by-products hconventional p

ATERIALS AND

nism And Media

lus delbrueck+) lactic acid p

Fig.1 Schem

om renewablemicroorganismchemical synlactic acid [

mbrane cell rvantageous thaw volumetric phigh labour co[9]. Uses of N

of undissociatedto be much mo) membranes. h such multifincreasing machieve desir

has been foundprocesses.

METHODS

a Preparation

kii (NCIM-20producing bacte

atic Diagram Of

e resources lm has receivnthesis route 6, 7].Continuo

recycle systeman batch procproductivities dost due to start

NF (nanofiltratiod L (+) lactic aore advantageoDevelopment

functional hybass transfer rared product

d to be promis

025), a homerium used in

f Membrane Inte

like ved

to ous

m is cess due t up on)

acid ous t of brid ate, by

ing

mo-our

work wMicroorPune, maintainsubsequPure sumainly filtered sugarcacontaine1fructosextract, MnSO4

1.5 g l-

Sigma A

B. Ex

The 2was prnitrogenreactor was a10agitationThe fermembrathe inlecirculati

egrated Reactor S

was brought frganisms (NCIndia in lyoned in MRS

uently in 50 mugarcane juice

used as fermeto remove un

ane juice colled 132.34 g lse. The media

7.69 g l-1 pep.4H2O, 1.5 g l1 K2HPO4. AlAldrich.

xperimental Eq

20 litre pilot provided with n gas purgingtemperature an0 litre stainlessn was maintairmenter was ane modules toet and the out lion across the

System For Lact

from NationalCIM), Nationophilized cond agar slants

ml MRS broth was purchase

entation medianwanted particllected in the l-1 sucrose, 7.was suppleme

ptone; 0.2 g l-1

l-1 sodium acetll the chemical

quipment

plant fermenterthermostatic

g system for nd anaerobic ens steel tank (Fined at 410C aequipped wi

o which pressulet. A peristaltmicrofiltration

tic Acid Product

l Collection onal Chemical dition. The

at 40C and in a 100 ml c

ed from local a. The juice wles like fibres,

months of 98 g l-1glucosented with 13.1 MgSO4.7H2Otate, 1.5 g l-1 l reagents use

r made up of swater circulatensuring desinvironment. Fe

Fig. 1).The temand 160 rpmith cross flowure gauges weric pump was u

n membrane mo

tion

of Industrial Laboratory,

culture was subcultured

conical flask. farmers and

was then pre- solids. Pure March-April

se, 5.65 g l-

82 g l-1yeast O, 0.005 g l-1

KH2PO4 and d were from

stainless still tion system, red constant eed reservoir

mperature and respectively.

w flat sheet re attached at used for feed odule (MF).


36

TmoHignanacicon(mexpwitForUSimpmowa

dwS

The microfiltrodules performgh pressure dinofiltration meid from unconntinuous op

microfiltration aperiment was th pore size ofr the nanofiltra

SA) was selpurities from

odule selected fas 0.01 m2.

C. Analyti

The samplesdifferent time inwere measuredSeries, India)

ration (MF) mmed cell separat

iaphragm pumembrane modunverted sugarseration with

and nanofiltraticarried out wi

f 0.2 to 0.45 μmation step, NF2ected throughlactic acid. Mfor microfiltrat

cal Assays

from fermentnterval and the

d by UV spec

membranes usetion from the f

mp (5-40 kgf/cles that helpeds and other ih two staion). Cross-floith PVDF lamim (Membrane 2 membrane (Sh investigatio

Membrane surfation as well as

tation broth wee absorbance otrophotometer

Fig.2 Con

ed in cross flfeed for recyclicm2) was usedd separation lacimpurities durage membranow microfiltratinated membraSolutions, USepro Membran

ons to separace area for eafor nanofiltrat

ere taken out aof those sample

(CECIL, 700

nventional Ferm

low ing. d in ctic ring nes tion ane A).

nes, rate ach tion

at es 00

at 620Instrusupernacid, concecolumDeteccarbohconceZorbananofiby pe1200)with LquantiSCIEN

mentation-Base

0 nm. Sampleuments, India) natants were csucrose, gluc

entration was qmn (Agilent Tector (DAD). hydrates (su

entrations wereax Carbohydrafiltrated sampleeak purity sof).Protein estimLowry’s methoified with iNTIFIC, USA.

ed Lactic Acid

es were then uat 12,000 rp

collected for thcose and fructquantified by echnologies, H

The measuucrose, glue done by RIDate Analysis e was determiftware tool of

mation of the sod. Minerals (individual ele.

d Production Sc

ultra–centrifugpm for 15 mhe analysis of Ltose. L (+) LUltron ES-OV

HPLC) with Durement of ucose and D detector wiColumn. Purned through thf HPLC (Agilsamples were (Na+, K+ and Mectrodes from

cheme

ged (Sigma minutes and

L (+) lactic Lactic acid VM Chiral iode Array all three

fructose) ith Agilent ity of the he analysis lent, series carried out Mg2+) were m Thermo


37

APro

Tscathicomprelacacihyd

Apropurlaclacprotonprohazinvmaof rouma

BMa

DsucprothelikeconjuicoptconsofcatlimbasQu

A. Conventiooduction Schem

The synthetic ale started arous method, Lmbination of esence of base ctonitrile is subid by using drochloric acid

HCN + CH3C

CH3CH (OH) CH3

Ammonium choduction procerified by activa

ctate is evaporactic acid. Gypsoduct in the prnne per metricoduction procezard as gypvestment cost iany units as shosuch a plant. T

ute of survivalanufacturing in

B. Batch and ajor Parameter

Design Expeccessfully applocess. Response present invese temperature, ncentration duce by Lactotimization resuntinuous run. ftware by setegorical facto

mits of yeast exsed on the exuadratic Model

III. RESULTS A

onal Fermenme

manufacture ound 1963 in Ja

Lactonitrile is hydrogen cyacatalyst in liq

bsequently pureither conc

d.

HO

CN + 2H2O + CH (OH) COO

hloride is proess. Lactic acidated carbon adsated and acidifisum (calcium rocess and is

c tonne of lactess is associasum disposals naturally veryown in the typ

Thus process inl and sustainab

ndustry.

Continuous Prs

ert Software lied to optimizese surface methstigation to opt

yeast extract curing lactic acobacillus delbults were alsoThe experime

electing threeor with one rextract, peptonexisting literatuwas suggested

AND DISCUSSIO

ntation-Based

of lactic acid apan and Unit

produced fianide and aceuid phase. Theified and hydrcentrated sul

CH3CH

HCL OH + NH 4Cl

duced as a byd is esterified sorption. In neied by sulphurisulphate) is prproduced at a

tic acid. Thus ated with a bil poses a py high due to i

pical schematicntensification ible developme

Process With

(Version 8.e lactic acid prhodology (RSMtimize the operconcentration acid productionrueckii (NCIMo useful in thnts were desig

e numeric faesponse. The e and temperatuure of lactic d by the softwa

ON

Lactic Aci

in a commercted states [10].irst due to taldehyde in e recovered cruolyzed into lacphuric acid

H (OH) CN

y-product in tby methanol a

ext phase, calciic acid to produroduced as a b

a rate of 1 metthe conventio

ig environmenproblem. Capinvolvement ofc diagram (Fig.is the only natuent of lactic a

Optimization

.0.4) has beroduction in baM) was chosenrating paramet

as well as pepton from sugarcaM-2025). Thhe proceeding gned through actors and zupper and lowures were choacid producti

are to evaluate

id

cial . In the the ude ctic

or

this and

as a resuin this pand hychemicaoxidatiocarbon pressureoxidatiocommerdependecater toproductbeen pre

productdownstrfiltrationthat proleads tothen sep

um uce by-tric

onal ntal ital f so . 2) ural acid

Of

een atch n in ters one ane ose

of the

zero wer sen ion. the

results. significaindicatevarianceconcentlactic ac

It waof lacttemperabeyond

ult it generatesprocess to pur

ydrolyzation unal synthesis ron of propylen

monoxide ane, hydrolysis on of propylercialized [11]ent on other bo the growingtion of biodegreferred to chem

Typical contion schemeream treatmentn, acidificationoduction proceo the productioparated from th

The Model F-ant. Value of

es that the moe (ANOVA) tration of yeastcid production

as observed frotic acid initiature up to 3941 OC, lactic a

s methyl lactatrify this recovender acidic croutes for lacne glycol, reacnd water at eof chloroprop

ene. But none] and those by-product ind

g demand of pradable PLA, mical synthesis

nventional ferm(Fig.2) con

t schemes like n, carbon adsoess addition oon of calcium he microbial ce

-value of 31.18‘P’ was 0.001 odel terms arhas shown tht extract and c.

om Fig.3 and Fially increased90C but as temacid concentrat

e. The other stered lactate arondition. Therctic acid proction of acetalelevated tempeionic acid and

e of these proprocesses b

dustries are expure L (+) lacthe fermentati

s route.

mentation basensists of a

precipitation, orption and evof lime for co

lactate. Calciuells by filtration

8 implies thatand being less

re significant. he effects of oncentration o

Fig.4 that the cd with the

mperature incretion started dec

teps involved re distillation re are other duction like ldehyde with eratures and d nitric acid ocesses were being often xpensive. To ctic acid for ive route has

ed lactic acid number of

conventional aporation .In

ontrolling pH um lactate is n and further

the model is s than 0.0500

Analysis of temperature,

of peptone on

concentration increase of

eased further creasing.


38

pepmutheproconhavlacwitwitsysextThproconparbeeof havvarexpcon3.2to ais 3totacleaffenv

At initial tempptone concentruch but as teme factors were oduction. Abncentration ofving negative ctic acid conceth the help of th same optistem was 116.2tract concentra

he production yoductivity. Ferncentration of rameters were en experimentalactic acid fromve significant riation in thperiments werndition (withou24) at the end oachieve undiss3.86 at 25 OC.al sugar is be

early presentedfected by pvironment resu

perature, with trations, lactic a

mperature increfound to have

bove 41OC f yeast extrac

effect on lacentration achief RSM model mized conditi28 g L-1 at 41OCation and 7.69yield achievedrmentations wf 5 % and 160

not included ally investigatem sugarcane jueffect on lacti

hat applied rre carried out ut pH adjustmof 72 hours basociated lactic How lactic ac

een consumed d in Fig.5. Prroduct-inhibiti

ulting in poor p

the increase ofacid concentraeased above 3e positive impa

temperature,ct and peptonctic acid produeved from pure

as well as thrions in memC temperature,9 g L-1 peptond was 93% wiere carried ou0 rpm of shakin optimizatio

ed that in the pruice, those paric acid producrange. All t

by adopting ment). Lower patch process wacid as pKa vacid concentratiwith time in

roduction in bion problem productivity.

f yeast extract aation did not v5 oC (upto410

act on lactic a even hig

ne concentratiouction. Optime sugarcane jurough experim

mbrane integra 13.82 g L-1 yene concentratiith 1.615 g L-

ut with inoculker speed. Th

on study as it hroduction procrameters does tion with smalthe fermentatnon neutraliz

pH obtained (pwas quite effect

alue of lactic aion increased abatch process

batch mode wand low

and vary 0C), acid gher ons

mum uice

ment ated east ion. 1h-1 um ose has

cess not ller tion zing pH- tive acid and s is was pH

cost, crecycle out withmembrasystemcan be desirabithe

To improve pontinuous prowas adopted.

h one stage meane separationpresented in Foptimized ac

ility of the pro

productivity anoduction procContinuous fe

embrane separan system due Fig.1. Again nuccording to thduct quantity.

nd to reduce thcess with meermentation caation system o

to the flexibumber of workhe nature of It was only po

he production mbrane cell

an be carried or multi stage bility of the king modules process and

ossible due to


39

super flexibility nature of the hybrid system. How lactic acid produced with time in continuous system and substrate is being consumed is clearly presented in Fig.6.We adopted two stage continuous membrane separation system to get pure, polymer grade L (+) lactic acid in industrial production level. In continuous production process first 15 hours was conducted with batch process and then fresh feed addition was started with membrane cell recycle process. It affects in the production trend of lactic acid and substrate consumption which is clearly shown in Fig.6. After almost 30 hours of continuous run with dilution rate of 0.15 hr-1 and cross flow velocity 0.53 ms-1, steady state condition achieved which is an important criterion of continuous run. Concentration of lactic

acid achieved in steady state condition was 82.68 g L-1. After nanofiltration with NF-2 membrane at 13 kg cm-2 operating pressure, lactic acid purely separated from other impurities at the concentration of 66.97 g l-1. Results are tabulated in Table 1.Our collected sugarcane juice contained 132.3 gL-1 sucrose, 7.9 gL-1 glucose, 5.6 gL-1 fructose. Total glucose and fructose got consumed within 6 hours of fermentation. After batch fermentation, continuous fermentation with microfiltration cell recycle was started with 6 litres working volume of the reactor. Cell recycling helped mainly in high cell concentration in the fermenter and thus contributed significantly to enhance production of lactic acid.

TABLE I

Lactic Acid Production From Sugarcane Juice In Batch And Continuous Process ___________________________________________________________________________________ Conditions Lactic acid Concentration Product Yield Productivity

(g L-1) Yps (%) (g L-1h-1) ___________________________________________________________________________________ Batch 116.28 93 1.615 (at 72 hrs) Continuous 82.68 96.5 12.40 ___________________________________________________________________________________

By operating four modules in microfiltration cell recycle system and 1 module in nanofiltration system the achieved flux was 76.6 l m-2 h-1, where complete separation of microbial cells and more than 95% removal of impurities were achieved. The purity of the sample was determined as 95% when sample peak was tested in HPLC peak purity software tool. Two stage flexible membrane system developed for continuous production of pure L (+) lactic acid was comparatively much more efficient and can be considered as environment-friendly, energy efficient, and economical alternative of conventional lactic acid production process. Over all modular design makes the process super flexible. Marinating liquid phase throughout the system makes the process eco-friendly as conventional process consist of lot of phase change operations like evaporation, crystallization. Uses of harsh chemical like H2SO4 and production of gypsum again makes conventional production process not favourable for environment. Large number of steps in conventional production process ultimately makes the process economically non-favourable. Development of such sustainable technology for clean production process of L (+) lactic acid must be encouraged by future process industries in the respect of process intensification. In the age of highly depleting natural resources like fossil fuel, such kind membrane based technology with the uses of fully renewable resource like sugarcane juice considers it an ideal alternative for conventional lactic acid production process.

IV. CONCLUSIONS

Due to the growing demand of L (+) lactic acid for the production of biodegradable plastic (PLA), it has been necessitated to improve conventional fermentation-based lactic acid production process with efficient and sustainable process. Membrane based hybrid reactor system successfully stands in that objective without creating any negative environmental impact. Super flexibility and operational simplicity makes the system ideal for the production of L (+) lactic acid in any industrial scale.. High productivity and purity achieved in this membrane-integrated fermentation system and in an absolutely environmentally benign process will definitely go in favor of its industrial adoption.

ACKNOWLEDGMENT

The authors are thankful to the Department of Science and Technology (DST), Government of India for the grants under DST-Green Technology Program (SR/S5/GC-05/2008).

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Developing Sustainability Technology For Chemical Process ...journalsweb.org/siteadmin/upload/58585 IJBEES 0102008.pdf · Developing Sustainability Technology For Chemical Process