process flow literature

8/19/2019 Process Flow Literature

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III. REVIEW ON PROCESS LITERATURE

Lactic acid can be synthesized industrially by two means either through chemically or by

microbial fermentation. However, the fermentation through microbes has some potential

advantages where pure lactic acid can be attained while, chemical synthesis of lactic acid always

give a racemixture. The commercial chemical production of lactic acid is based primarily on

lactonitrile. Hydrogen cyanide is added to the acetaldehyde in presence of a base to make

lactonitrile. The reaction ccurs at high atmospheric pressures in liquid phase. hile production

of lactic acid by fermentation processes is an energy yielding process in which organic molecules

play role as both electron donors and electron acceptors. The molecule which is metabolized

does not possess its whole potential energy extracted from it. Therefore, lactic acid bacteria are

widely used as a cheap method for food maintenance by fermentation and usually no or little heat

is required in fermentation.

3.1 RAW MATERIAL PREPARATION

!"ruit based industry produces large volume of wastes, both solids and liquids# these

wastes pose increasing disposal and pollution $high %&' or (&') problems and represent a loss

of valuable biomass and nutrients. However these carbohydrate rich wastes can be tuned as


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valuable substrates for the commercial production of organic acids like lactic acid and thus can

be regarded as a viable option for meeting the growing demand for lactic acid *mesh $+ - )./!The commercial production of lactic acid using fermentation technology mainly depends

on the cost of raw material used. Therefore, it is compulsory to select a raw material for

industrial production of lactic acid with a number of characteristics such as low cost, rapid rate

of fermentation, lowest amount of contaminants, high yields of lactic acid production, little or no

formation of by0products and availability for whole year 1affar $+ - )./!2ccording to the 3ournal by 4awad $+ -+), mango peel as a by0product of mango

processing industry could be a rich source of bioactive compounds, and enzymes such as

protease, peroxidase, polyphenol oxidase, carotenoids, vitamins ( and 5, dietary fibers, enzymesand carbohydrate content of + .6 7+6.+ 8 in dry weight samples of mango peel. "urthermore,

mango peels have been shown to be a rich source of flavonol &0 and xanthone (0glycosides,

gallotannins and benzophenone derivatives. However, reports on the use of mango peels for the

production of industrially relevant metabolites such as lactic acid through fermentation processes

are rare. Thus, cultivation of microorganisms on these wastes may be a value0added process

capable of converting these materials, which are otherwise considered to be wastes, into valuable

products through processes with techno0economic feasibility./

!2ccording to the patent of 9eikotlhaile $+ - ), pesticide residues have been found in

various fruits and vegetables# both raw and processed. &ne of the most common routes of

pesticide exposure in consumers is via food consumption. :ost foods are consumed after passing

through various culinary and processing treatments. 2 few literature reviews have indicated the

general trend of reduction or concentration of pesticide residues by certain methods of food

processing for a particular active ingredient. However, no review has focused on combining the

http://www.sciencedirect.com/science/article/pii/S027869150900492Xhttp://www.sciencedirect.com/science/article/pii/S027869150900492X


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stability of the enzyme towards the denaturing action of solvent, detergents, proteolythic nzymes,

and a decrease in the viscosity of the reaction medium at higher temperatures, etc./ !%asic parameters which affect the hydrolysis process 7 temperature, pH of the medium,

concentration of the substrate and concentration of the enzyme 7 usually vary depending on the

source of the enzyme. :ost often the hydrolysis with thermally resistant 7 amylase is carried out

at a temperature G 0- C( D+,?E, concentration of the substrate in the suspensions varying from

+ 8 to BA8 D+,A,?, E, pH between ? and 6, and enzyme concentration . B 7 -8 D+,?, E./!Lactic acid production processes traditionally suffer from end0product inhibition. 2n

undissociated lactic acid passes through the bacterial membrane and dissociates inside the cell.

The inhibition mechanism of lactic acid is probably related to the solubility of the undissociatedlactic acid within the cytoplasmic membrane and the insolubility of dissociated lactate, which

causes acidification of cytoplasm and failure of proton motive forces. >t eventually influences the

transmembrane pH gradient and decreases the amount of energy available for cell growth$29,88 ). Therefore, to alleviate the inhibitory effect of lactic acid during the fermentation, it must

be removed selectively in situ from the fermentation broth ee $+ ?)./>n the preparation of mango peel before fermentation from the method by 4awad $+ -+),

!The washed mango peels were cut into small pieces and blended with ultra pure water in the

ratio $-F-) $wIv) using an electrical food processor $9enwood) at +A J( for A min. The humidity

of the washed mango peels to the air dried mango peels before staring the fermentation process

was calculated to be --7-B8. hile, the humidity of mango peels after mixing with water to be

in the fermentation suspension form was found to be G-. 8. The pH of the blended peel was

ad3usted using - : of Ka&H or H(l and thereafter, B mL was dispensed into conical flasks of

- mL capacity./ >n the method used by *mesh $+ - ), for the preparation of hydrolysates for

fermentation of fruit peel, !the modified method of ;uimput et. al., + 6 was used for substrate

hydrolysate preparation. 2bout 6gram of each fruit peel waste was steam exploded in an


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autoclave at -+-J( for + min. =terile water was added to the wet pretreated material to make the

volume of + ml and boiled at 6 J( for B min followed by filtration with cheese cloth. 2cid

hydrolysis of filtrate was carried out by autoclaving at -+-J( with concentration of -8 H(l vIv

for B min. The pH of the hydrolysate after hydrolysis was ad3usted with (a& to ?0?.6 and the

(a=& precipitate formed was removed by filtration with hatman filter paper Ko.-./

3.2 REACTIONS

2ccording to 1affar $+ - ), !Lactic acid can be synthesized industrially by two meanseither through chemically or by microbial fermentation. However, the least one $fermentation

through microbes) has some potential advantages e.g. pure lactic acid can be attained whereas,

chemical synthesis of lactic acid always give a racemic mixture./!:ost of the world s commercial lactic acid is prepared by fermentation of carbohydrates

by bacteria, using homolactic microbes such as a variety of modified or optimized strains the

genus Lactobacilli, which especially produce lactic acid. (ommercially pure lactic acid can be

synthesized by microbial fermentation of the following carbohydrates such as glucose, sucrose,

lactose, and starchImaltose derived from feed0stocks such as beet sugar, molasses, whey, and

barley malt. The preference of feedstock entirely depends on its price, availability, and on the

respective costs of lactic acid recovery and purification. %iomass of lignocelluloses is a low0cost

and extensively available renewable carbon source as an alternative to these conventional feed0

stocks that has no challenging food value &ther biological agents capable of producing lactic

acid are also used such as strains of Mhizopus, 5scherichia, %acillus, 9luyveromyces and

=accharomyces./


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!The commercial procedure for chemical synthesis of lactic acid is based on lactonitrile.

Hydrogen cyanide is added to the acetaldehyde in presence of a base to make lactonitrile. The

reaction ccurs at high atmospheric pressures in liquid phase. The crude of lactonitrile is

recovered. ;urification is done by distillation. Then it is hydrolyzed to lactic acid, either by

concentrated H+=& or by H(l to produce the resultant lactic acid and ammonium salt. 2fter

that lactic acid is esterifies by methanol to produce methyl lactate before purification through

distillation, and then hydrolyzed by water in the presence of acid catalyst to produce methanol

and lactic acid. The chemical synthesis process produces a racemic mixture of 'L0lactic acid.

"ollowing reactions are involved in this process./!;roduction of lactic acid by fermentation processes "ermentation is an energy yielding

process in which organic molecules play role as both electron donors and electron acceptors. The

molecule which is metabolized does not possess its whole potential energy extracted from it.

Therefore, lactic acid bacteria are widely used as a cheap method for food maintenance by

fermentation and usually no or little heat is required in fermentation./!>n batch fermentation process the culture is first grown in a series of inoculums vessels

and after that transferred to the fermentor. The size of inoculum is usually Ae- 8 of the liquid

volume in this fermentor. The fermentation is usually kept at BA0 A C( and at pH A0?.A by adding

a suitable base, such as ammonium hydroxide. &ther fermentations for lactic acid production are,

fed0batch, repeated batch, and continuous batch. %ut the higher concentration of lactic acid has

achieved in batch and fed0batch cultures than in others, whereas higher productivity has obtained

by continuous cultures. 2nother advantage of the continuous batch over batch culture is that the

process can be run for a long period of time./

B.+.+ 2ccording to the 3ournal by ee $+ ?)


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!%atch, fed0batch, repeated batch, and continuous fermentations are the most frequently

used methods for lactic acid production. Higher lactic acid concentrations may be obtained in

batch and fed0batch cultures than in continuous cultures, whereas higher productivity may be

achieved by the use of continuous cultures. 2nother advantage of the continuous culture

compared to the batch culture, is the possibility to continue the process for a longer period of

time./

B.+.B 2ccording to the 3ournal by Mao $+ )

!"ermentation using lactic acid bacteria is widely used in food fermentation. The lactic

acid bacteria need to withstand varying environmental conditions including differences intemperature, pH and salinity, depending on the specific application. 2n enhanced salt and pH

resistance of lactic acid bacteria is attractive in shrimp waste, fish, vegetables and seafood

fermentation./

B.+. 2ccording to


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fermentation. Hetero fermentative lactic acid bacteria ferment - mole of glucose to - mole of

lactic acid, - mole of ethanol, and - mole of (&+. &ne mole of 2T; is generated per mole of

glucose, resulting in less growth per mole of glucose metabolized. %ecause of the low energy

yields, lactic acid bacteria often grow more slowly than microbes capable of respiration, and

produce smaller colonies of + 7 B mm./

:icroorganisms for the lactic acid ;roduction

!There are large number of species of bacteria and some species of molds that possess the

ability to form relatively significant quantities of lactic acid from carbohydrates. Lactic acid

bacteria are important not only for the desirable reactions which they catalyze but also for theundesirable activities which they promote./

!%acteria and fungi are the two groups of microorganisms that can produce lactic

acid.2lthough most investigations of lactic acid production were carried out with lactic acid

bacteria $L2%), filamentous fungi such as Rhizopus , utilize glucose aerobically to produce lactic

acid. Rhizopus species such as R. oryzae and R. arrhizus have amylolytic enzyme activity, which

enables them to convert starch directly to L$N)0lactic acid, but it also requires vigorous aeration

because R. oryzae is an obligate aerobe. >n fungal fermentation, the low production rate, below P

@ B g L7- h7- is probably due to the low reaction rate caused by mass transfer limitation. The

lower product yield from fungal fermentation is attributed partially to the formation of

byproducts./!=everal attempts have been made to achieve higher cell density, lactic acid yield, and

productivity in fungal fermentation. Haung et al . produced lactic acid from potato starch

wastewater using R. oryzae and R. arrhizus . ;ark et al. produced lactic acid from waste paper by

using R. oryzae . Tay and Oang-6 immobilized R. oryzae cells in a fibrous bed to produce lactic


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acid from glucose and starch. 9osakai et al. cultured R. oryzae cells with the use of mycelial floc

formed by the addition of mineral support and poly ethylene oxide./!1arde et al. obtained lactic acid from wheat straw hemicellulose by using mixed culture

of Lactobacillus pentosus and Lactobacillus brevis. Oun et al. investigated the production of

lactic acid from single and mixed sugars using Enterococcus faecalis RKY1 . The volumetric

productivity, cell growth and concentration of lactic acid were highest in glucoseIfructose $mixed

sugar) than single sugar. Mivas et al . produced lactic acid from corn cobs by simultaneous

saccharification and fermentation using Lactobacillus rha nosus ./! ee et al. reported the economical L$N)0lactic acid production from sugar molasses by

batch fermentation of Enterococcus faecalis . 9ourkoutas et al . used immobilized Lactobacilluscasei cell on fruit pieces to produce lactic acid. Karita et al. reported the efficient production of

L$N)0lactic acid from raw starch by !treptococcus bovis 1"8. (hauhan et al . used the statistical

screening of medium components by ;lacket0%urman design for lactic acid production by

Lactobacillus sp . K#P$1 using date 3uice. ;atil et al. produced lactic acid from cane sugar using

mutant of Lactobacillus %elbruec&ii '#() 2*+ . 4ohn et al. reported the solid state fermentation

for L0lactic acid production from agro wastes using Lactobacillus %elbruec&ii. 2mrane and

;rigen designed a two0stage continuous reactor to produce lactic acid from lactose by using

lactobacillus helveticus and obtained high product concentration of lactic acid at very low

dilution rate./!=enthuran et al . explained lactic acid production by immobilized Lactobacillus casei in

recycle batch reactor. "u and :athewsB reported the lactic acid production from lactose by

Lactobacillus plantaru . Kolasco0Hipolito et al. BA explained the continuous production of L$N)0

lactic acid from hydrolyzed sago starch using Lactobacillus lactis . 2mraneB? reported the

unstructured models for biomass formation, substrate consumption and lactic acid production

from whey using Lactobacillus helveticus ./


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!Kancib et al . explained the 3oint effect of nitrogen sources and %0vitamin

supplementation of date 3uice on lactic acid production by Lactobacillus casei sub sp.

rha nosus. &h et al . used agricultural resources for the production of lactic acid by

Enterococcus faecalis . =chepers et al. reported the continuous lactic acid production in whey

permeate with immobilized Lactobacillus helveticus . &hkouchi and >noue studied the direct

production of L$N)0lactic acid from starch and food wastes using Lactobacillus anihotivorans

L)- 18$11 .


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acid bacteria, such as Lactobacillus a ylophilus Lactobacillus a ylovorus and Lactobacillus

plantaru 0+ can convert starch directly to lactic acid. The most common bacterium for the

industrial production of lactic acid is Lactobacillus %elbruec&ii, which is employed in

fermentations utilizing corn dextrose media. &ther bacteria of industrial importance include

Lactobacillus bul aricus , which utilizes lactose as a carbon source and finds use in lactic acid

production from whey media, and Lactobacillus pentosus , which is able to utilize the pentoses of

sulfite waste liquor./

B.+.A 2ccording to the 3ournal by :uller $+ -)

!Lactate is a common end product of fermentations. =ome organisms, collectively calledthe lactic acid bacteria, form large amounts of lactate. Lactic acid bacteria are subdivided

according to their fermentation products. The homofermentative species produce a single end

product, lactic acid, whereas the heterofermentative species produce other compounds, mostly

ethanol and carbon dioxide, along with lactate. These differences are due to the employment of

different pathways for glucose oxidationF in homofermentative organisms glucose breakdown is

via glycolysis according to glucose to lactate./

B.+.? 2ccording to the 3ournal by *mesh $+ - )

!The research work evaluates the fermentative utilization of fruit peel wastes $mango,

orange, banana and pineapple) as substrates for lactic acid production by employing

Lactoctobacillus plantarum as the starter culture. Thus the presentstudy highlights a methodology

for recycling, reprocessingand eventual utilization of fruit waste for beneficial uses rather than

their discharge to the environment which might cause detrimental environmental effects./!The optimal growth temperature, pH and Ka(l concentration for the growth of

L.plantarum was found to be B J(,pH ? and +8 Ka(l. 2nalysis of the technological properties

of the culture was primarily done to evaluate its feasibility to be employed as a starter culture for


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industrial fermentation. The acidification activity analyses showed thatthe isolated L.plantarum

strains exhibited medium acidification range of .?A to . - QpH $change in pH) after ? hrs./!The highest lactic acid production was obtained from themango peels $- . 6 gIL) ,

whereas the other substrates viz.orange, banana and pineapple peels produced A. gIL, .?6 gIL

and .?6 gIL of lactic acid respectively. Thus the present study highlights a methodology for

recycling, reprocessingand eventual utilization of fruit waste for beneficialuses rather than their

discharge to the environmentwhich might cause detrimental environmental effects./

B.+. 2ccording to the results of study by Mao

!"our Lactobacillus species were studied for their ability to grow at high Ka(l

concentrations and different initial pH values. 2mong these strains, Lactobacillus plantarum

strains A - and 2? indicated to be the most salt tolerant. %oth strains were able to ferment

glucose up to 68 salt and produce lactic acid even at - 8 salt. "or strain A -, the specific rate of

lactate production $qlac) and the yield of lactic acid relative to substrate $OpIs) remained constant

up to ?8 salt whereas the yield of biomass relative to substrate $OxIs) decreased at higher salt

concentrations. >n contrast, for strain 2?, OpIs decreased up to ?8 salt whereas OxIs did not vary

markedly. 2t 68 salt, decreasing performance in final biomass and lactic acid production was

observed. %oth strains were able to reduce pH to values lower than . within + h. 2 factorial

design was applied to study combined effects of salt and initial pH on the fermentation

parameters. >t is shown that salt and pH do not interact significantly within the established

experimental domain, and that pH is the more dominant factor. (onsidering overall performance,

it is concluded that 8 salt and pH between ?. 0?.? can be taken as appropriate conditions, for

the use of both strains as starter in processes where higher salt concentrations are preferred./


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3.2.8 According to Parker Domnick Hunter | Process Filtration - Buyers Guide

( tt!s"##$$$.!arker.com#literature#Domnick%2&Hunter%2&Process

%2&Filtration%2&Di'ision#PAFD literature#)i*e%2&+ciences

%2&)iterature#,nderstanding%2& acterial%2&and%2&! age

%2&contaminations.!d*

/0icro ial *ermentations are used *or t e !roduction o* a $ide 'ariety

o* !roducts including io! armaceuticals1 en ymes1 amino acids and

anti iotics. ontaminations caused y acteria or ! age can a'e a

signi4cant 4nancial im!act u!on manu*acturers as *ermentation ra$

materials must e re!laced1 additional do$ntime *or root cause analysis

incurred and delays to t e !roduction sc edule diminis *acility !roducti'ity.

Des!ite muc eing $ritten regarding t e maintenance o* ase!tic conditions

*or t e duration o* *ermentations contaminations continue to occur. 5 e

*ollo$ing article is intended as a !ractical guide to understanding $ y

contaminations occur in order to reduce t e risk o* t eir *uture occurrence.6

!Misk of contamination depends on the process "ermentation processes can vary greatly

in their scale, duration and complexity which relate to their purpose. =ome fermentations are

more susceptible to contaminations these include those that utilize nutrient0rich medias# contain

slow growing organisms# take a protracted length of time# are performed under moderate

temperature and pH ranges./!2 more complex process which uses multiple feeds and a high sampling frequency

correlate with an increased risk of contamination. The detrimental effects of these additional

operations on process robustness should be considered although they are frequently ignored as

http://buyersguide.waterworld.com/parker-domnick-hunter-process-filtration.htmlhttps://www.parker.com/literature/Domnick%20Hunter%20Process%20Filtration%20Division/PAFD_literature/Life%20Sciences%20Literature/Understanding%20bacterial%20and%20phage%20contaminations.pdfhttps://www.parker.com/literature/Domnick%20Hunter%20Process%20Filtration%20Division/PAFD_literature/Life%20Sciences%20Literature/Understanding%20bacterial%20and%20phage%20contaminations.pdfhttps://www.parker.com/literature/Domnick%20Hunter%20Process%20Filtration%20Division/PAFD_literature/Life%20Sciences%20Literature/Understanding%20bacterial%20and%20phage%20contaminations.pdfhttps://www.parker.com/literature/Domnick%20Hunter%20Process%20Filtration%20Division/PAFD_literature/Life%20Sciences%20Literature/Understanding%20bacterial%20and%20phage%20contaminations.pdfhttp://buyersguide.waterworld.com/parker-domnick-hunter-process-filtration.htmlhttps://www.parker.com/literature/Domnick%20Hunter%20Process%20Filtration%20Division/PAFD_literature/Life%20Sciences%20Literature/Understanding%20bacterial%20and%20phage%20contaminations.pdfhttps://www.parker.com/literature/Domnick%20Hunter%20Process%20Filtration%20Division/PAFD_literature/Life%20Sciences%20Literature/Understanding%20bacterial%20and%20phage%20contaminations.pdfhttps://www.parker.com/literature/Domnick%20Hunter%20Process%20Filtration%20Division/PAFD_literature/Life%20Sciences%20Literature/Understanding%20bacterial%20and%20phage%20contaminations.pdf


14/25

process performance is easier to quantify than the risk of process failure. &nce a contamination

has occurred the contaminating organism should be identified. :any manufacturers will be

aware of the organisms they typically encounter in their local environment. (ontamination by an

organism that has been previously encountered might indicate a common source./

(ontaminations in small0scale fermenters

!%ench0scale fermenters are used in laboratories for research or development while large0

scale fermenters with capacities of hundreds of thousands of litres are used for the commercial

scale production of biomass, metabolites and enzymes. =mall0scale fermenters are typically

designed for process flexibility rather than operating robustness. The ingress of contaminatingmicrobes in these fermenters can occur by the following routesF =ilicone tubing used to deliver

feeds to the fermenter where insufficient care has been taken with tubing connections# Through

bottom entry stirrer seal assemblies where a single0mechanical seal has been used and is not

being continuously supplied with steam in order to prevent a hot spot# >mproperly connected air

vent filters# >mproper cleaning of the sparger# ;oor tightening of the fermenter top lid screws./!(ontaminations in production0scale fermenters ;roduction fermenters are more heavily

engineered and typically hard0piped with contaminations being more frequently attributable to

tainted inocula or failures in the sterilization of liquids and gases entering the vessel. "ailure to

inoculate fermenters with a pure culture of the producer organism is likely to lead to be

damaging to the process if the contaminating organism can compete with the producer under the

conditions within the vessel./

(ontaminated inocula

!The isolation of pure cultures is critical to avoiding frequent contaminations. :ethods

for isolating pure cultures include dilution to extinction, pour plating and streak plating.

'eveloping production strains requires considerable time, effort and expense. &nce the


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development is complete the culture should be appropriately stored either at reduced temperature

or by storage in a dehydrated form. The quality of these stock cultures should be monitored in

order to ensure purity, viability and productivity by culturing in shake flasks and observing a

characteristic growth profile. The preparation of an inoculum from the stored stock of cells

requires manual operations during which the risk of contamination occurring is increased. 1ood

laboratory aseptic technique is required through the inoculum preparation process. =amples

should be taken throughout this process even though the results are unlikely to be available

before the inoculum reaches the production process. 'etection of unwanted microbial species in

these samples facilitates root causes analysis when contaminations occur./!The contamination of fermenters has a significant financial impact on manufacturers.

The likely source of a contamination may depend on scale or the complexity of the fermentation

process being operated. The prevention of contaminations can be achieved by good equipment

design, the following of standard operating procedures and a detailed understanding of the

various sterilization processes that ensure a sterile barrier is maintained around the fermenter.

"iltration can be used for the sterilization of liquids and gases entering the fermenter. ;re0

filtration of air entering the fermenter can help protect against phage contaminations./!Mesearchers concluded that %oth Lactobacillus plantaru strains can produce lactic acid

and reduce the pH to values lower than . at salt concentrations up to 68. 2t high salt

concentrations uncoupling between growth and energy production indicates that lactic acid

production is still possible even in detrimental conditions for growth. "actorial designs indicate

for both L. plantaru strains, that salt and pH did not interact significantly within the

experimental domain and that pH was the most determining factor for glucose fermentation, in

the range of salt concentration tested./!'epending on the strains and parameters, maximum specific growth rate, cell biomass

and lactic acid production were at salt concentrations of either -.B8 or +.A8. However since the


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ability of both strains to grow without lag phase up to 8 salt, it is concluded that a 8 salt

concentration and initial pH between ?. and ?.? can be a good compromise for their use. These

more drastic conditions would still allow an efficient lactic acid production to prevent growth of

spoilage microorganisms. (onsidering that either L. plantaru A - or 2? present potential to be

used in processes containing high salt concentration, the choice of one of the two strains for raw

material processing will depend mainly on the type of carbohydrate to be added in. >f glucose is

planned to be used as a growth substrate for acidification, strain A - would be preferred to strain

2?.!Kotwithstanding, for economical reasons the use of other alternative carbon sources,

containing complex carbohydrates such as starch or glycogen, may be preferred. "or instance,

the ability of strain 2? to ferment glycogen contained in mussel processing wastes has been

reported $;intado et al. -GGG). The use of this type of wastes would present economical

advantages. &ther types of seafood processing wastes might also be considered for lactic acid

production, which opens a broad range of applications to be investigated./

3.3 SEPARATION

B.B.- 2ccording to the 3ournal by


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procedure converts all of the lactic acid to calcium lactate, kills bacteria, coagulates protein of

the medium, removes excess calcium carbonate and helps to decompose any residual sugar in the

medium. n

one procedure, the heated and filtered fermentation broth is concentrated to allow crystallization

of calcium lactate, followed by addition of sulfuric acid to remove the calcium as calcium

sulfate./!The lactic acid is then re0crystallized as calcium lactate, and activated carbon is used to

remove colored impurities. 2s an alternative to the latter step, the zinc salts of lactic acid are

sometimes prepared because of the relatively lower solubility of zinc lactate. >n other procedure,

the free lactic acid is solvent extracted with isopropyl ether directly from the heated and filtered

fermentation broth. This is a counter current continuous extraction, and the lactic acid is

recovered from the isopropyl ether by further counter0current washing of the solvent with water.

>n a third procedure, the methyl ester of the free lactic acid is prepared, and this is separated from

the fermentation broth by distillation followed by hydrolysis of the ester by boiling in dilute

water solution $the methyl ester decomposes in water)./!The lactic acid is then obtained from the aqueous solution by evaporation of the water,

and the methanol is recovered by distillation. >n a fourth procedure, secondary or tertiary alkyl

amine salts of lactic acid are formed and then extracted from aqueous solution with organic

solvents# the solvent is removed by evaporation, and the salt then is decomposed to yield the free

acid. 2n older procedure, not utilized commercially to any extent today, involves direct high0

vacuum steam distillation of the lactic acid from the fermentation broth, but decomposition of

some of the lactic acid occurs./!The fermentation broth is generally heated to J( to kill the bacteria and then acidified

with sulfuric acid to pH -.6. The clarified lactic liquor is then ion exchanged and concentrated to

6 8. =mell and taste can be improved further by oxidative treatment with hydrogen peroxide.


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The lactic acid obtained at this stage is suitable for some food industries. The lactic acid

produced from biological fermentation requires extensive purification operations. >t is of

particular importance that the recovery processing equipment be resistant to the corrosive

action of the high concentrations of lactic acid that accumulate. Therefore, special stainless steel

equipment is most often employed for this purpose./

B.B.+ 2ccording to the 3ournal by Taskila $+ -+)

!%iotechnical production of lactic acid may be based on several alternative micro0

organisms. >n addition to lactic acid bacteria filamentous fungi $ e. . Rhizopus spp.), other gram0

positive bacteria $ e. . /acillus coa ulans ) and metabolically engineered yeasts have been used

also in industrial scale. The advantage of fungi is that they are active at and tolerate low medium

pH. Low pH reduces significantly the consumption of neutralizing agent $(a$&H)+) in the

fermentation stage and subsequent formation of gypsum $(a=& ) in the product recovery stage./!The advantage of filamentous fungi, /acillus spp. and yeasts compared to lactic acid

bacteria is their simple nutrient requirement in the fermentation medium. "ilamentous fungi and

/acillus spp. are better suited to lignocellulosic fermentation raw materials as they are in general

able to utilize pentose sugars in addition to hexoses. 2naerobic fermentation is generally

speaking more feasible and this favors yeasts and lactic acid bacteria. hen optimized the

technical parameters such as product yield, M; and final product concentration are quite similar

for each of these production organisms./

B.B.B. 2ccording to 'unuwila $+ B) =eparation ;rocess for %iobased Lactic 2cid

!2ll commercially viable, lactic acid0producing microorganisms presently require

neutralization during fermentation to ensure that the pH does not become low enough to kill the

microbes. To obtain the acid, a cation elimination process is necessary, wherein the base cation


19/25

needed to neutralize the acid during fermentation is replaced by protonation. ;reviously, several

strategies have been pursued by a number of researchersF/!The gypsum process, wherein sulfuric acid is used to acidify the calcium salt of lactic

acid $calcium lactate is produced by neutralizing the fermentation broth with lime), results in

stoichiometric production of calcium sulfate $gypsum), which has low quality and limited

commercial value. %oth the acid and the base are irreversibly consumed during the associated

chemical processes./!5lectrodialysis, which uses a conventional concentrating electrodialysis step followed

by watersplitting electrodialysis to convert the salt to acid and base, is an alternative. Kumerous

economic studies have indicated that this process is costly in both capital $membranes) andoperating costs $electrical power), and probably is not feasible for commodity chemical

production./!5xtraction of lactic acid by polar organic solvents, water0soluble trialkyl amines, and

water0immiscible long0chain trialkyl amines in the presence of pressurized carbon dioxide have

been studied. Kone of these techniques is commercially viable because of long residence times

and large processing volumes./!The proposed separation process was designed to overcome the limitations of the

existing technologies. "urthermore, the technical challenges associated with the unit operations

of the proposed separation process were identified. ;lausible solutions for investigation during

;hase >> will be proposed./

B.B. 2ccording to efthilia 2rvaniti, :ichael 1oldsworthy et al.

/:icrobial cells were removed using filtration or flocculation. Then lactic acid solvent

extraction or distillation is then used to purify the product. >t can be purified further by use of

activated carbon and ion0exchange resins, other techniques include electrodialysis or purification

via intermediate ester formation./


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B.B.A 2ccording to Ki3u Karayanan et al.

!The broth containing calcium lactate is filtered to remove cells, carbon treated,

evaporated and acidified with sulphuric acid to get lactic acid and calcium sulphate. The

insoluble calcium sulphate is removed by filtration# lactic acid is obtained by hydrolysis,

esterification, distillation and hydrolysis./

B.B.? 2ccording to >.= *dachan et al.

!Two0step process was used in separating and purifying lactic acid first by liquid0liquid

extraction followed by back extraction, liquid liquid extraction was done using trioctylamine as

extractant. Then to recover the lactic acid back extraction was used and the solution was reacted

with KaoH./

3.4 PURIFICATION

B. .- 2ccording to the 3ournal by


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and 6 8. >t is prepared by employing sulfuric acid to remove the calcium from the calcium

lactate derived from the heated and filtered fermentation broth, followed by filtration,

concentration, and refiltration to remove additional calcium sulfate. Thus, this grade of lactic

acid contains many of the impurities from the fermentation medium, and it finds many industrial

uses where purity of the product is not essential as, for example, in the deliming of hides in the

leather industry.

B. .+ 2ccording to the 3ournal by 1haffar $+ - )

!The recovery of lactic acidmust be improved in order to reduce lactic acid losses and to increase

purity. ;urification or product recovery is an important step in production of lactic acid that isassociated with separation and purification of lactic acid form fermentation broth. "ermentation

broth contains a number of impurities such as residual sugars, color, nutrients and other organic

acids, as part of cell mass.These impurities must be removed from the broth in order to

achievemore pure lactic acid./!To recover and purify the L$R)0lactic acid produced from the microbial fermentation

media economically and efficiently, ion exchange chromatography is used among the variety of

downstream operations. >t is extremely selective and gives product recovery at very low cost

within a short period of time. The other purposes were to analyze the end product purity, to check

adsorption or desorption behaviors of lactic acid and to examine the applicability of this method

for industrial usage./

B. .B 2ccording to the 3ournal by 9omesu $+ -B)

!The development of an efficient method of separation and purification of the lactic acid

from fermentation broth is very important, since these steps are responsible for A 8 of the


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production costs. 2 considerable amount of researches have done a great deal of work on the

purification procedures./!Hybrid short path evaporation is an alternative separation process with potential for

recovery and concentration of thermally unstable molecules such as lactic acid. >t has been

recognized as a potential method because of its low evaporation temperature and short residence

time that minimize thermal decomposition problems./

B. . 2ccording to 5vangelista $-GG )

!Lactic acid was purified by filtration, carbon treatment and evaporation. 2ctivated

carbon is mixed with the crude extract to remove the colored components. The spent carbon is

then filtered out and the filtrate is sent to the evaporator where excess water is evaporated under

mild vacuum at moderate temperature $ .A atm and J() to B 8 calcium lactate concentration.

This preparation is then acidified with ?B8 sulfuric acid to precipitate calcium sulfate, which is

filtered out. The lactic acid is bleached a second time and then evaporated to A+ or 6+8

concentration./!Lactic acid was purified by calcium lactate crystallization. The crude extract is bleached

with activated carbon and then acidified slightly before undergoing a second bleaching. 5xcess

water is evaporated under vacuum to obtain a density of -.-+ kgIm. 2t this concentration,

calcium lactate crystallizes upon cooling. The crystals may be redissolved, treated with sodium

sulfide to remove heavy metals, bleached, and recrystallized to improve purity./!Lactic acid was purified by liquid0liquid extraction The crude extract is filtered,

acidified with sulfuric acid and the resulting calcium sulfate precipitate is filtered out. The crude

lactic acidis bleached with activated carbon and the heavy metals, calcium, and amino acids are removed

by ion exchange. 5xcess water is evaporated under vacuum to about 8 lactic acid

concentration before it enters the countercurrent extraction columns. The lactic acid is extracted


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by diisopropyl ether in the first countercurrent extraction column. The extracted aqueous solution

still contains + 8 of the total lactic acid in the crude lactic acid, which can be concentrated

further for technical applications. The acid is recovered from the solvent by countercurrent

extraction into water in the second countercurrent extraction column. the remaining solvent is

boiled off from the aqueous solution and the acid is concentrated by evaporating the excess water

to obtain food0grade lactic acid. The product is relatively free from ash but may contain other

impurities from raw materials./!Lactic acid was purified by esterification and distillation (rude lactic acid is fed into a

heated reactor where it reacts with methanol under the influence of small amounts of sulfuric

acid.The molar ratio of lactic acid to methanol is kept at -F-.A. The vapors distilling from the reactor

consist of methyl lactate, methanol, and water, with traces of lactic acid. This mixture is

introduced into the middle of a fractionating column. :ethanol, the most volatile component,

rises to the top of the column, and is collected, condensed to a liquid and returned to the reactor.

The bottom fraction contains methyl lactate, lactic acid and water, which are collected in a kettle.

Hydrolysis of the methyl lactate takes place in the fractionating column and is completed in the

kettle. The methanol is boiled off and sent back to the reactor via the fractionating column./

B. .A 2ccording to =un et al.

!They used two reactors with a rectifying column carried out recovery of lactic acid

from the fermentation broth. 2mmonium lactate obtained by fermentation was used directly to

produce butyl lactate by reacting with butanol for ? h, and the esterification yield of ammonium

lactate was 6 . 8 cation exchange resin which was modified by =n(l+ replaced sulphuric acid

as a catalyst, and neutral ammonium lactate replaced former lactic acid as a starting material

butyl lactate was rectified, and the purified butyl lactate was sequentially hydrolyzed into lactic


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acid in presence of the cation exchange resin in the HN form as a catalyst for h, and the

hydrolysis yield was 6G. 8 and the purity of recovered lactic acid was G 8./

B. .? 2ccording to 4.


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B. .6 2ccording to garde, 2rvid et al.!The first separation process is a microfiltration process for removal of cells, colloids and

particles. 5lectrodialysis process lactate and other ionic material are concentrated. ater is

removed from the diluate circuit of the electrodialysis by an reverse osmosis unit to insure a

satisfactorilyconductivity. >n the nanofiltration process divalent cations are retained and

removed. %y adding an inorganic acid before nanofiltration lactate is converted to lactic acid./!The lactic acid is extracted through anion0exchange membranes, driven by a

combination of diffusion and electrical migration. 2n alkaline solution on the other side of the

membranescollects the lactate ions. Hydroxide ions flows back into the fermentation broth, cleaning the ion0

exchange membranes from organic buildup of fouling and replacing the removed lactate ions./

process flow literature

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