International Journal of Biological, Ecological and Environmental Sciences (IJBEES) Vol. 1, No. 2, March 2012 ISSN 2277 – 4394
Developing Sustainability Technology For Chemical
Process Industry: Lactic Acid by Membraneintegrated Hybrid Process
P. Pal, P. Dey
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 fermentationbased 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
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
I
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 environmentfriendly, 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
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(+)
Environment & Membrane Technology Laboratory, Department of Chemical
Engineering, National Institute of Technology, Durgapur, West Bengal713209, 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
35
International Journal of Biological, Ecological and Environmental Sciences (IJBEES) Vol. 1, No. 2, March 2012 ISSN 2277 – 4394
lacctic acid production
fro
om renewablee resources like
l
suggarcane juice with suitable microorganism
m has receiv
ved
higgh acceptance compared to chemical syn
nthesis route to
prooduce optically pure L(+) lactic acid [6, 7].Continuo
ous
ferrmentation pro
ocess with membrane cell recycle
r
system
m is
muuch more econ
nomically adv
vantageous thaan batch proccess
whhich suffers larrgely from low
w volumetric productivities
p
due
d
to end product in
nhibition and high labour co
ost due to startt up
N (nanofiltratio
on)
andd shut-down prrocedures [8]-[9]. Uses of NF
meembranes for th
he separation of
o undissociated
d L (+) lactic acid
a
in permeate site is turned out to
t be much mo
ore advantageo
ous
verse osmosis) membranes. Developmentt of
thaan the RO (rev
proocess intensification through
h such multiffunctional hyb
brid
meembrane reacto
or system by increasing mass transfer raate,
prooductivity, selectivity to achieve desirred product by
sepparating other by-products has
h been found
d to be promising
alteernative to the conventional processes.
p
was brought ffrom Nationall Collection oof Industrial
work w
Microorrganisms (NC
CIM), Nationnal Chemical Laboratory,
Pune, India in lyoophilized conddition. The culture was
maintainned in MRS agar slants at 40C and subcultured
subsequuently in 50 m
ml MRS broth in a 100 ml cconical flask.
Pure suugarcane juice was purchaseed from local farmers and
mainly used as fermeentation mediaa. The juice w
was then prefiltered to remove unnwanted particlles like fibres, solids. Pure
sugarcaane juice colllected in the months of March-April
containeed 132.34 g l-1 sucrose, 7.98 g l-1glucosse, 5.65 g l1
fructosse. The media was supplemeented with 13.82 g l-1yeast
extract, 7.69 g l-1 pepptone; 0.2 g l-11 MgSO4.7H2O
O, 0.005 g l-1
-1
-1
MnSO4 .4H2O, 1.5 g l sodium acettate, 1.5 g l KH2PO4 and
1.5 g l- 1 K2HPO4. Alll the chemicall reagents used were from
Sigma A
Aldrich.
B. Exxperimental Eqquipment
The 220 litre pilot pplant fermenterr made up of sstainless still
was prrovided with thermostatic water circulattion system,
nitrogenn gas purgingg system for ensuring desired constant
reactor temperature annd anaerobic ennvironment. Feeed reservoir
Fig. 1).The tem
mperature and
was a100 litre stainlesss steel tank (F
agitationn was maintaiined at 410C aand 160 rpm respectively.
The ferrmenter was equipped wiith cross flow
w flat sheet
membraane modules too which pressuure gauges werre attached at
the inleet and the out llet. A peristaltic pump was uused for feed
circulatiion across the microfiltrationn membrane moodule (MF).
A
AND METHODS
II. MATERIALS
A
A. Microorgan
nism And Media
a Preparation
Lactobacillus delbrueckkii (NCIM-20
025), a hom
mo+) lactic acid producing
p
bacteerium used in our
ferrmentative L (+
Fig.1 Schematic Diagram Off Membrane Inteegrated Reactor S
System For Lacttic Acid Producttion
36
International Journal of Biological, Ecological and Environmental Sciences (IJBEES) Vol. 1, No. 2, March 2012 ISSN 2277 – 4394
T
The microfiltrration (MF) membranes
m
useed in cross fllow
moodules perform
med cell separattion from the feed
f
for recycliing.
Higgh pressure diiaphragm pum
mp (5-40 kgf/ccm2) was used
d in
nannofiltration meembrane modules that helped
d separation lacctic
aciid from uncon
nverted sugarss and other impurities
i
durring
conntinuous operation with
h two staage membran
nes
(m
microfiltration and
a nanofiltratiion). Cross-flo
ow microfiltrattion
expperiment was carried out wiith PVDF lamiinated membraane
witth pore size off 0.2 to 0.45 μm
m (Membrane Solutions, USA).
Forr the nanofiltraation step, NF2
2 membrane (Sepro Membran
nes,
US
SA) was selected through
h investigatio
ons to separrate
imppurities from lactic acid. Membrane
M
surfaace area for eaach
moodule selected for
f microfiltrattion as well as for nanofiltrattion
waas 0.01 m2.
at 6200 nm. Samplees were then uultra–centrifugged (Sigma
Instruuments, India) at 12,000 rppm for 15 m
minutes and
supernnatants were ccollected for thhe analysis of L (+) lactic
acid, sucrose, gluccose and fructtose. L (+) L
Lactic acid
VM Chiral
conceentration was qquantified by Ultron ES-OV
mn (Agilent Teechnologies, H
HPLC) with Diode Array
colum
Detecctor (DAD). The measuurement of all three
(suucrose,
gluucose
and
carbohhydrates
fructose)
conceentrations weree done by RID
D detector wiith Agilent
Zorbaax Carbohydraate Analysis Column. Purity of the
nanofi
filtrated samplee was determined through thhe analysis
by peeak purity sofftware tool off HPLC (Agillent, series
1200)).Protein estim
mation of the ssamples were carried out
Lowry’s methood. Minerals ((Na+, K+ and M
Mg2+) were
with L
quantiified with iindividual eleectrodes from
m Thermo
SCIEN
NTIFIC, USA..
C. Analytical Assays
a
The samples from fermenttation broth weere taken out at
ddifferent time in
nterval and thee absorbance of
o those samplees
w
were measured
d by UV spectrophotometer (CECIL, 700
00
S
Series, India)
nventional Ferm
mentation-Baseed Lactic Acidd Production Sccheme
Fig.2 Con
37
International Journal of Biological, Ecological and Environmental Sciences (IJBEES) Vol. 1, No. 2, March 2012 ISSN 2277 – 4394
III. RESULTS AND DISCUSSIO
ON
A
A. Conventio
onal
Prooduction Schem
me
Fermen
ntation-Based
Lactic
as a resuult it generatess methyl lactate. The other stteps involved
in this pprocess to purrify this recoveered lactate arre distillation
and hyydrolyzation unnder acidic condition. Therre are other
chemicaal synthesis rroutes for lacctic acid production like
oxidatioon of propylenne glycol, reacction of acetalldehyde with
carbon monoxide annd water at eelevated tempeeratures and
pressuree, hydrolysis of chloropropionic acid andd nitric acid
oxidatioon of propyleene. But nonee of these proocesses were
commerrcialized [11]] and those processes bbeing often
dependeent on other bby-product inddustries are exxpensive. To
cater too the growingg demand of ppure L (+) lacctic acid for
producttion of biodegrradable PLA, the fermentatiive route has
been preeferred to chem
mical synthesiss route.
Aciid
T
The synthetic manufacture of
o lactic acid in a commerccial
scaale started arou
und 1963 in Jaapan and Unitted states [10].. In
this method, Lactonitrile
L
is produced fiirst due to the
mbination of hydrogen cyaanide and acetaldehyde in the
com
preesence of base catalyst in liquid phase. Thee recovered cru
ude
lacctonitrile is sub
bsequently purified and hydrolyzed into lacctic
aciid by using either conccentrated sulphuric acid or
hyddrochloric acid
d.
HCN + CH3CHO
Typical connventional ferm
mentation baseed lactic acid
producttion scheme (Fig.2) connsists of a number of
downstrream treatmentt schemes like precipitation, conventional
filtrationn, acidificationn, carbon adsoorption and evaporation .In
that prooduction proceess addition oof lime for coontrolling pH
leads too the productioon of calcium lactate. Calciuum lactate is
then sepparated from thhe microbial ceells by filtrationn and further
CH3CH
H (OH) CN
CH3CH (OH) CN + 2H2O + HCL
OH + NH 4Cl
CH3CH (OH) COO
A
Ammonium ch
hloride is produced as a by
y-product in this
t
prooduction proceess. Lactic acid
d is esterified by methanol and
a
purrified by activaated carbon adssorption. In neext phase, calcium
lacctate is evaporaated and acidifiied by sulphuriic acid to produ
uce
lacctic acid. Gypssum (calcium sulphate) is prroduced as a byb
prooduct in the prrocess and is produced at a rate of 1 mettric
tonnne per metricc tonne of lacttic acid. Thus the conventio
onal
prooduction proceess is associaated with a biig environmen
ntal
hazzard as gypsum disposall poses a problem.
p
Capital
invvestment cost is naturally very
y high due to involvement
i
off so
maany units as sho
own in the typ
pical schematicc diagram (Fig.. 2)
of such a plant. Thus
T
process in
ntensification is
i the only natu
ural
ble developmeent of lactic acid
a
rouute of survivall and sustainab
maanufacturing in
ndustry.
results. The Model F--value of 31.188 implies that the model is
significaant. Value of ‘P’ was 0.001 and being lesss than 0.0500
indicatees that the moodel terms arre significant. Analysis of
variancee (ANOVA) has shown thhe effects of temperature,
concenttration of yeastt extract and concentration oof peptone on
lactic accid production.
B
B. Batch and Continuous Process
P
With Optimization Of
Maajor Parameterrs
D
Design Expeert Software (Version 8..0.4) has beeen
succcessfully appllied to optimizee lactic acid prroduction in baatch
proocess. Responsse surface meth
hodology (RSM
M) was chosen
n in
thee present invesstigation to opttimize the operrating parametters
likee temperature, yeast extract concentration
c
as
a well as pepto
one
conncentration du
uring lactic accid production
n from sugarcaane
juicce by Lacto
obacillus delbrueckii (NCIM
M-2025). Those
opttimization resu
ults were also
o useful in th
he proceeding of
conntinuous run. The experiments were desig
gned through the
sofftware by seelecting threee numeric faactors and zero
z
cattegorical facto
or with one reesponse. The upper and low
wer
lim
mits of yeast ex
xtract, peptonee and temperatu
ures were chosen
bassed on the ex
xisting literatu
ure of lactic acid productiion.
Quuadratic Model was suggested
d by the softwaare to evaluate the
It waas observed froom Fig.3 and F
Fig.4 that the cconcentration
of lacttic acid initiially increasedd with the increase of
temperaature up to 3990C but as tem
mperature increeased further
beyond 41 OC, lactic aacid concentrattion started deccreasing.
38
International Journal of Biological, Ecological and Environmental Sciences (IJBEES) Vol. 1, No. 2, March 2012 ISSN 2277 – 4394
At initial temp
perature, with the
t increase off yeast extract and
a
pepptone concentrrations, lactic acid
a
concentraation did not vary
v
muuch but as tem
mperature increeased above 35 oC (upto410C),
thee factors were found to havee positive impaact on lactic acid
a
prooduction. Ab
bove 41OC temperature, even hig
gher
conncentration off yeast extracct and pepton
ne concentratio
ons
havving negative effect on lacctic acid produ
uction. Optim
mum
lacctic acid conceentration achieeved from puree sugarcane ju
uice
witth the help off RSM model as well as thrrough experim
ment
witth same optimized conditiions in mem
mbrane integraated
sysstem was 116.2
28 g L-1 at 41OC temperature, 13.82 g L-1 yeeast
exttract concentraation and 7.69
9 g L-1 pepton
ne concentratiion.
Thhe production yield
y
achieved
d was 93% wiith 1.615 g L-1h-1
prooductivity. Ferrmentations were carried ou
ut with inoculum
conncentration off 5 % and 160
0 rpm of shak
ker speed. Those
parrameters were not included in optimizatio
on study as it has
h
beeen experimentaally investigateed that in the prroduction proccess
of lactic acid from
m sugarcane ju
uice, those parrameters does not
havve significant effect on lactiic acid production with smalller
varriation in th
hat applied range.
r
All the
t
fermentattion
expperiments werre carried out by adopting non neutralizzing
conndition (withou
ut pH adjustm
ment). Lower pH
p obtained (p
pH3.224) at the end of
o 72 hours baatch process was
w quite effecttive
to aachieve undisssociated lactic acid as pKa vaalue of lactic acid
a
is 33.86 at 25 OC. How lactic accid concentratiion increased and
a
totaal sugar is beeen consumed with time in batch processs is
cleearly presented
d in Fig.5. Prroduction in batch
b
mode was
w
afffected by product-inhibitiion problem and low pH
envvironment resu
ulting in poor productivity.
p
To improve pproductivity annd to reduce thhe production
cost, continuous prooduction proccess with membrane cell
recycle was adopted. Continuous feermentation caan be carried
out withh one stage meembrane separaation system oor multi stage
membraane separationn system due to the flexibbility of the
system presented in F
Fig.1. Again nuumber of workking modules
can be optimized acccording to thhe nature of process and
desirabiility of the product quantity. It was only poossible due to
the
39
International Journal of Biological, Ecological and Environmental Sciences (IJBEES) Vol. 1, No. 2, March 2012 ISSN 2277 – 4394
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.
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
TABLE I
Lactic Acid Production From Sugarcane Juice In Batch And Continuous Process
___________________________________________________________________________________
Conditions
Lactic acid Concentration
Product Yield Productivity
Yps (%)
(g L-1h-1)
(g L-1)
___________________________________________________________________________________
Batch
116.28
93
1.615 (at 72 hrs)
Continuous
82.68
96.5
12.40
___________________________________________________________________________________
IV. CONCLUSIONS
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.
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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40
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