Scholarly article on topic 'Recent trends in lactic acid biotechnology: A brief review on production to purification'

Recent trends in lactic acid biotechnology: A brief review on production to purification Academic research paper on "Agriculture, forestry, and fisheries"

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Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Tayyba Ghaffar, Muhammad Irshad, Zahid Anwar, Tahir Aqil, Zubia Zulifqar, et al.

Abstract Lactic acid is one of the most important organic acid which is being extensively used around the globe in a range of industrial and biotechnological applications. From its very old history to date, many methods have been introduced to improve the optimization of lactic acid to get highest yields of the product of industrial interests. In serious consideration of the worldwide economic and lactic acid consumption issues there has been increasing research interest in the value of materials with natural origin, which are cheap, abundant and easily available all around the year. Recent trends showed that lactic acid production through fermentation is advantageous over chemical due to the environmental concerns of the modern world. The eco-friendly processing and fermentable capability of many of the agricultural and agro-industrial based raw materials or by-products respectively makes them attractive candidates in fermentation biotechnology to produce a value-added product with multiple applications. In fact, major advances have already been achieved in recent years in order to get pure lactic acid with optimal yield. The present review work is summarized on the multi-step processing technologies to produce lactic acid from different substances as a starting material potentially from various agro-industrial based biomasses. The information is also given on a purification through schematic representation of the product of quality interests.

Academic research paper on topic "Recent trends in lactic acid biotechnology: A brief review on production to purification"

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Recent trends in lactic acid biotechnology: A brief review on production to purification

Tayyba Ghaffara, Muhammad Irshada'*, Zahid Anwar a, Tahir Aqilb, Zubia Zulifqara, Asma Tariqa, Muhammad Kamrana, Nudrat Ehsana, Sajid Mehmood a

a Department of Biochemistry, NSMC, University of Gujrat, Pakistan b Department of Botany, University of Gujrat, Pakistan

ARTICLE INFO

ABSTRACT

Article history: Received 8 February 2014 Received in revised form 11 March 2014 Accepted 15 March 2014 Available online xxx

Keywords:

Green biotechnology Lactic acid Fermentation Product optimization Purification

Lactic acid is one of the most important organic acid which is being extensively used around the globe in a range of industrial and biotechnological applications. From its very old history to date, many methods have been introduced to improve the optimization of lactic acid to get highest yields of the product of industrial interests. In serious consideration of the worldwide economic and lactic acid consumption issues there has been increasing research interest in the value of materials with natural origin, which are cheap, abundant and easily available all around the year. Recent trends showed that lactic acid production through fermentation is advantageous over chemical due to the environmental concerns of the modern world. The eco-friendly processing and fermentable capability of many of the agricultural and agro-industrial based raw materials or by-products respectively makes them attractive candidates in fermentation biotechnology to produce a value-added product with multiple applications. In fact, major advances have already been achieved in recent years in order to get pure lactic acid with optimal yield. The present review work is summarized on the multi-step processing technologies to produce lactic acid from different substances as a starting material potentially from various agro-industrial based biomasses. The information is also given on a purification through schematic representation of the product of quality interests.

Copyright © 2014, The Egyptian Society of Radiation Sciences and Applications. Production

and hosting by Elsevier B.V. All rights reserved.

* Corresponding author. Tel.: +92 344 4931030.

E-mail addresses: mirshad.uog@gmail.com, muhammad.irshad@uog.edu.pk (M. Irshad). Peer review under responsibility of The Egyptian Society of Radiation Sciences and Applications

http://dx.doi.Org/10.1016/j.jrras.2014.03.002

1687-8507/Copyright © 2014, The Egyptian Society of Radiation Sciences and Applications. Production and hosting by Elsevier B.V. All rights reserved.

1. Background introduction

From the histological point of view lactic acid has a long history of uses for fermentation and was first discovered in 1780 by Swedish chemist, Carl Wilhelm Scheele, who isolated the lactic acid from sour milk as an impure brown syrup and gave it a name based on its origins: 'Mjolksyra'. After nine years around in 1789, Lavoisier named this milk component "acide lactique", which became the core origin of the current terminology for lactic acid. For a very long time until 1857 it was being considered a milk component while later on that year Pasteur discovered another phenomenon and postulated lactic acid as a fermentation metabolite generated because of the involvement of certain microorganisms. In support with Pasteur's discovery a French scientist Fremy produced lactic acid by fermentation and this gave rise to first industrial production of lactic acid in the United States by a microbial process in 1881. From that time it has Wide applications in food, pharmaceutical, cosmetic and chemical industries etc (Narayanan, Roychoudhury, & Srivastava, 2004). The worldwide demand for lactic acid is estimated roughly to be 130 000 to 150 000 tons per year (Randhawa, ahmed, & akram, 2012). However, the global consumption of lactic acid is expected to increase rapidly in the near future (Wee, Kim, & Ryu, 2006).

2. Common aspects in the synthesis of lactic acid

Lactic acid can be synthesized industrially by two means either 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 raceme mixture (Randhawa et al., 2012). The existence of l(+)-

lactic acid which have high optical purity provides polylactic acids with high crystallinity and high melting point (Oh et al., 2005). One of the most expanding uses of lactic acid is its use in polymerization of lactic acid to form polylactic acid (PLA), a polymer of great interest because it can be produced from renewable means which is biodegradable in nature. Fig. 1 illustrates the production of PLA using starch as a potential starting substrate. Many PLA-based products are already available in the market, where they are used to replace the petroleum-based consumables (Ilmen, Koivuranta, Ruohonen, Suominen, & Penttila, 2007). Lactic acid is the simplest hydroxy acid which has an asymmetric carbon atom and is present in two optically active forms. In humans and other mammals only the l(+)- isomer is present, whereas the d(-)- and l(+)-both enantiomers can synthesized using an appropriate bacterial strains. Therefore, most 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. Commercially pure lactic acid can be synthesized by mi-crobial fermentation of the following carbohydrates such as glucose, sucrose, lactose, and starch/maltose derived from feed-stocks 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. Biomass of lignocelluloses is a low-cost and extensively available renewable carbon source as an alternative to these conventional feed-stocks that has no challenging food value (Pang, Zhuang, Tang, & Chen, 2010). Other biological agents capable of producing lactic acid are also used such as strains of Rhizopus, Escherichia, Bacillus, Kluyveromyces and Saccharomyces (Maas et al., 2008).

Widely used method for the production of lactic acid is Batch fermentation. Conditions for Fermentation are different for each industrial method but are usually in the range of 45-60 °C having a pH of 5.0-6.5 for Lactobacillus delbrueckii and

Fig. 1 - Production of Poly-L-lactic acid using starch as a substrate.

43 °C with a pH of 6.0-7.0 for Lactobacillus bulgaricus. The acid synthesized is neutralized by calcium hydroxide or calcium carbonate (Zhou, Causey, Hasona, Shanmugam, & Ingram, 2003). Fermentation takes 1-2 days under optimal lab conditions. The yield of lactic acid after the fermentation stage is 90-95 wt% based on the initial sugar or starch concentration. Rate of fermentation depends mainly on the parameters such as pH, temperature, initial substrate concentration and concentration of nitrogenous nutrients (Zhou et al., 2003). There has been a great interest in solving the issues such as PLA weakens at high temperature for the purpose to enhance the use of this renewable plastic (Omay & Guvenilir, 2012). Hydrolysis reaction of methyl lactate is use to enhance the performance of batch reactive distillation to produce lactic acid (Edreder, Mujtaba, & Emtir, 2010). Lactic acid bacteria are conventionally particular microbes that have complex nutrient necessities industrial wastes of food which have high moisture and loaded in carbon source have been considered as an eye-catching nutrient source for industrial production of lactic acid (Randhawa et al., 2012). Product recovery is an important step in lactic acid production that is associated to separation and purification of lactic acid from fermentation broth (Chakkrit, 2010). A conventional procedure for lactic acid production by lactose fermentation involves the purification steps that are necessary to attain the pure lactic acid. Alternatives to this industrialized procedure are being studied. Numerous studies on lactic acid purification have been conducted by using several different techniques for separation such as ion exchange, reactive extraction, membrane technology, distillation and electro-dialysis (Gonzalez, Alvarez, Riera, & Alvarez, 2008).

2.1. Chemical synthesis of lactic acid

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 occurs at high atmospheric pressures in liquid phase. The crude of lactonitrile is recovered. Purification is done by distillation. Then it is hydrolyzed to lactic acid, either by concentrated H2SO4 or by HCl to produce the resultant lactic acid and ammonium salt. After 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 dl-lactic acid. Following reactions are involved in this process (Boontawan, Kanchanathawee, & Boontawan, 2011).

(a) Addition of Hydrogen CyanideCatalyst

Catalyst

(c) Esterification CH3CHOHCOOH + CH3OH CH3 / CHOHCOOCH3 + H2O

> CH3CHOHCN

Lactonitrile

CH3CHO + HCN

Acetaldehyde Hydrogen cyanide

(b) Hydrolysis by H2SO4

CH3CHOHCN +H2O + 1/2 H2SO4 /

Lactonitrile Sulphuric acid

CH3CHOHCOOH +12 (NH4)2SO4A

Lactic acid

Lactic acid Methanol

(d) Hydrolysis by H2O

Methyl lactate

Ammonium salt

CH3CHOHCOOCH3 +H2O/ CH3CHOHCOOH + CH3OH

Methyl lactate Lactic acid Methanol

2.2. Production of lactic acid by fermentation processes

Fermentation 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 (Boontawan et al., 2011). In 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 5-10% of the liquid volume in this fermentor. The fermentation is usually kept at 35-45 °C and at pH 5-6.5 by adding a suitable base, such as ammonium hydroxide (Gonzalez, Alvarez, Riera, & Alvarez, 2007). Other fermentations for lactic acid production are, fed-batch, repeated batch, and continuous batch. But the higher concentration of lactic acid has achieved in batch and fed-batch cultures than in others, whereas higher productivity has obtained by continuous cultures. Another advantage of the continuous batch over batch culture is that the process can be run for a long period of time (Vijayakumar, Aravindan, & Viruthagiri, 2008). l(+) lactic acid is produced commercially in fermentation processes by lactic acid bacteria or fungi such as Rhizopus oryzae in submerged culture. Rhizopus sp. can manufacture l(+) lactic acid from starch but the yield is very low as compared to lactic acid bacteria. 85% yield of l(+) lactic acid can be achieved using an airlift bioreactor under optimal conditions. The mycelia are not suitable enough for lactic acid as their morphology does not suit for fermentation because they increase the viscosity of the medium. They wrap up around the impellers and cause obstruction during sampling and in overflow lines. Small pellets of mycelia of R. oryzae are produced regulating the concentration of inoculated spores in pre culture. But there is a problem with pellets that they have insufficient mass transfer. Cotton like flock morphology can be obtained by mineral supports (Narayanan et al., 2004). An Overview of two production methods is given in the Fig. 2 (Vijayakumar et al., 2008; Wee et al., 2006).

3. Role of microbial cultures in lactic production

Lactic acid bacteria are generally gram-positive bacteria. They are non-motile, have non-spore-forming rods and cocci. They do not synthesize porphyrins and cytochromes there for why they cannot generate ATP. Lactic acid bacteria grow under anaerobic conditions as they do not use oxygen for their energy manufacture, but they are also capable of growing in the presence of oxygen. They remain protected from byproducts

of oxygen (e.g. H2O2) due to peroxidases they have and are aero tolerant anaerobes. They are distinguished from other organisms because of their capability to ferment hexoses to lactic acid. They are divided generally in two categories according to their fermentation patterns, homo fermentative and hetero fermentative bacteria (Vijayakumar et al., 2008).

Microorganisms which have capability to ferment cheap raw materials rapidly, require small amount of nitrogenous nutrients, provide high yields of required stereo specific lactic acid under low pH and high temperature conditions, produce small amounts of cell mass and slight amounts of other byproducts are industrially desirable (Narayanan et al., 2004). Most of the lactic acid production was carried out by using microorganisms such as lactic acid bacteria (LAB), and filamentous fungi, e.g. Rhizopus. They utilize glucose in aerobic conditions to produce lactic acid. Rhizopus species, R. oryzae and R. arrhizus, can convert starch directly to l(+)-lactic acid due to their amylolytic enzyme activity (Wee et al., 2006). Fungi have drawn a great attention in Lactic acid production such as R. oryzae. industrial fermentation has been improved the yield of the desired product by using The immobilization property of microorganisms which has been attractive for

Fig. 2 - A schematic representations of the two manufacturing processes of lactic acid.

industrial fermentation (Tanyildizi, Bulut, Selen, & Ozer, 2012). Efforts have been made to improve the production of lactic acid through metabolic engineering approaches (Wee et al., 2006). Yeasts, such as Saccharomyces cerevisiae, are more resistant to low pHs as compared to lactic acid bacteria. genetically engineered yeast has been prepared for producing lactic acid and has applied for large-scale production on experimental basis (Ishida et al., 2005). Mixed culture of Lactobacillus pentosus and Lactobacillus brevis were used by Garde to produce lactic acid from wheat straw hemicelluloses. Yun established the production of lactic acid using Entero-coccus faecalis RKY1 from single and mixed sugars (Vijayakumar et al., 2008). Escherichia coli were also used for the production of l-lactate and d-lactate. JP203 (pta:Tn5 phoA_-lacZ ppc:cat supE hsdS ara proAlacY galK rpsL xyl mtl), were reported as the best E. coli strains for production of d-lactate, the strain has numerous antibiotic resistance genes (kan and tet) (Zhou et al., 2003). Enterococcus faecium No. 78 has been used for the production of lactic acid in repeated batch fermentation mode. It was separated from puto, which is a type of fermented rice in the Philippines sago starch was used as the sole carbon source which was enzymatically liquefied (Nolasco-Hipolito et al., 2012). A Bacillus sp. strain 2-6 has been isolated for production of l-lactic acid at 55uC from soil samples. It is a good lactic acid producer because of its thermo-phillic characteristic and optically pure l-lactic acid can be formed by this strain under open circumstance without any sterilization (Qin et al., 2009).

4. Raw material for lactic acid production

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 by-products and availability for whole year (Randhawa et al., 2012).

E. faecalis has been used to hydrolyze Agricultural resources such as wheat, barley, and corn by commercial amylolytic enzymes RKY1 and fermented into lactic acid. Lactic acid productivities obtained were at >0.8 g/L h although no added nutrients were provided to those resources, using barley and wheat (Oh et al., 2005). Attempts have been also made for lactic acid production from sugar cane molasses as a cheap raw substrate through fermentation by using indigenous bacterial culture (L. delbrueckii). The conditions are optimized for fermentation taking into consideration fermentation time, substrate level and temperature as factors for main process.

Recently several authors have reported the valorization of lignocellulosic materials by biotechnology elsewhere in different sectors in addition with their suitable applications (Anwar, Gulfraz, & Irshad, 2014; Asgher, Shahid, Kamal, & Iqbal, 2014; Iqbal, Kyazze, & Keshavarz, 2013; Shahzadi et al., 2014). Lignocellulosic biomass was used for the production of lactic acid as an alternate to above conventional feed-stocks (Fig. 3). Lignocellulose is composed of and cellulose and hemicullolose that is made up of hexose and pentose sugar

surrounded in phenolic polymer lignin matrix. the main procedure relies on hydrolysis by cellulolytic and hemicellulolytic enzymes to obtain sugars from lignocelluloses which are fermentable. A pretreatment, either chemical or mechanical is required of the lignocellulose to reduce the size of particle, to remove the lignin or to modify it and to improve the convenience of the polysaccharides for the purpose of enzymatic hydrolysis (Maas et al., 2008). Supplementation of fermentation media is very necessary for the fast production of lactic acid with adequate nutrients. Yeast extract is used as the most general nutrient for production of lactic acid, but this may cause of increase in production costs considerably. A byproduct from the process of corn steeping has been utilized effectively for lactic acid production as an alternate. Since the corn steep liquor is derived from corn, 85% of its nitrogen content consists of amino acids, peptides and proteins (Wee et al., 2006). For production of optically pure D-lactic acid from raw glycerol, five technical schemes have been planned. These were pretended and assessed economically based on five fermentative scenarios by using engineered strains of E. coli (Posada, Cardona, & Gonzalez, 2012).

5. Optimization of lactic acid fermentation

A range of procedure variables have been optimized in the production of lactic acid using wastes raw materials as a substrate. It has been found that productivity is affected by temperature, fermentation time and the level of substrate. The highest yield has been obtained after 7 days of fermentation in media possessing 18% substrate level having a mean value of 7.76 ± 0.08 g/100 mL (77.6 g/L) at temperature of 42 °C. The maximum recovery was 78.30%.of lactic acid with respect to initial whole sugar contents of the media (9.91 ± 0.20 g/

100 mL) (Randhawa et al., 2012). R. oryzae NRRL 395 which immobilized in polyurethane foam has been used in Lactic acid production by using response surface methodology. Three independent variables; pH, glucose concentration, and rate of agitation has been explained by a 23 full-factorial central composite design (Tanyildizi et al., 2012). Maximum production of lactic acid was achieved 93.2 g/L by using a glucose concentration of 150 g/L, pH of 6.39 and rate of agitation 147 rpm. Agitation rate and concentration of glucose have found to be as limiting factors. So, any variation in these parameters can alter the production of lactic acid. Lactic acid production is not affected by the Initial pH due to neutralizing agent added. Production of lactic acid under optimum conditions using immobilized whole cells was calculated about 55% that is higher than the lactic acid production from suspension culture systems (Tanyildizi et al., 2012). In another study, calcium alginate has been utilized to immobilize L. delbruecfeii bacteria by using pineapple waste. Various important factors such as temperature, pH, calcium alginate concentration, beads diameter and inoculum size have to be consider systematically for the successful production of lactic acid. Yeast strains having heterologous l-lactate dehydrogenases can be used for lactic acid production. As these microbes can survive in acidic environments, it was identified that at low pH, cells are stressed by lactic acid (Valli et al., 2006). Two low-cost nitrogen sources such as yeast autolysate (YA) and corn steep liquor (CSL) have been used for The production of d(-) lactic acid with Lactobacillus LMI8 sp. To verify maximal lactic acid production a central composite design was used. The results of the experiments have evaluated by surface response methodology. The assays were carried in Erlenmeyer flasks of 250 mL consisting of 100 mL of production medium which was maintained by refrigerated incubation at a temperature of 37 ± 1 °C for 48 h at 200 rpm. CSL and interactions between CSL

I».1«. -; -V/W»*™--^ ^.IIHHI';:' .»'i i' "WJfc

Sugarcane waste Banana waste Barley waste Peanut husk

Fig. 3 - Lignocellulosic substrates for lactic acid production.

and YA was found to be affecting significantly Lactic acid production. Maximum production of d(+) lactic acid calculated was 41.42 g/L - a central value, which corresponded to 5 g/L of YA and 15 g/L of CSL (de Lima, Coelho, Blanco, & Contiero, 2009). Two response surface methodologies including central composite designs have been applied successfully to assess the effect of corn steep liquor, cheese whey, ammonium sulfate, and pH and temperature control on lactic acid fermentation by using Lactobacillus sp. LMI8 which was isolated from wastewater of cassava flour. In the first design, ammonium sulfate and corn steep liquor were investigated as cheap nitrogen sources in a combination with some other components to replace yeast extract for economical production. The best results have been achieved with 15 g/L of corn steep liquor, 55 g/L of lactose and 5.625 g/L of ammonium sulfate. A second central composite design has been applied After explaining the optimal nutritional conditions for production of lactic acid, to determine the level to which pH and temperature affect the lactic acid production with the aim of improving the fermentation production (Edreder et al., 2010). Production of lactic acid by immobilized cells of Lactococcus lactis IO-1 from glucose has been studied using cells immobilized either by encapsulation in microcapsules or entrapment in beads of alginate in membrane of alginate. The process is optimized by Taguchi method using shake flasks and then further processed in a production bioreactor (Sirisansaneeyakul et al., 2007).

6. Purification of lactic acid

The recovery of lactic acid must be improved in order to reduce lactic acid losses and to increase purity (Gonzalez et al., 2008). Purification or product recovery is an important step in production of lactic acid that is associated with separation and purification of lactic acid form fermentation broth. Fermentation 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 achieve more pure lactic acid. To recover and purify the l(+)-lactic acid produced from the microbial fermentation media economically and efficiently, ion exchange chromatography is used among the variety of downstream operations. It 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. Process strengthening and monomer grade lactic acid has been achieved in high purity by advancement of a new membrane-integrated technology. It has lesser the processing steps, chemical requirement and energy expenditure. The fastidious modular design provides a great elasticity in action of the system which the modern industrialized sector is looking for dreadfully in this era of shrunken profit edge. With the optimized participation of nanofiltration and microfiltration membrane modules in a steady production system, a logically high change of 76-77 L/m-2 h-1 has gained for a bigger than 95% pure l(+) lactic acid (Pal & Dey, 2012). Commercial production of pure lactic acid has also been carried out in many areas using strong-acid cation-exchange resins as solid catalysts (Zhang, Ma, & Yang, 2004). Surface active molecules such as enzymes and proteins are separated in aqueous solution by a simple and low cost method known as foam separation. Applicability and efficiency of foam separation technique has been studied by lactic acid broth, yeast extract and spent brewer's residual beer was used to examine the partial purification of products and recovery of important components from industrial waste stream (Kurt, 2006). Investigation has been carried out to check the usability of nanofiltration in a definite process of lactic acid production based on old bipolar electro-dialysis operations. DK nanofiltration membrane was used for recovery rate and purification of lactic acid efficiency. Magnesium and calcium ions are removed by nanofiltration efficiently from a sodium lactate fermentation broth before its conversion and concentration by electrodialysis (first level of potential integration). Maximum removal of impurities and lactic acid recovery has been achieved at maximum pressures of transmembrane. Phosphate and Sulfate ions are also partially

Fig. 4 - Substantial purification of lactic acid from fermentation broths by several membrane-based unit operations (columns).

removed (40% rejection). Lactic acid can also be extracted from aqueous solution using n-butanol as an extractant. Factors such as pH, mixing time, initial concentration of lactic acid, and volume ratio between the organic and the aqueous phase affect the extraction of lactic acid. Degree of lactic acid extraction and distribution coefficient increases when the pH of aqueous solution is decreased. The pH effect is considerably marked when the pH of the aqueous solution is less than 1. Initial concentrations of lactic acid and organic-to aqueous volume ratio appear to have positive effect on the degree of extraction and distribution coefficient. As the n-butanol is miscible partially in water, so integration of aqueous phase into organic phase in the extraction has a great organic-to-aqueous volume ratio (Chawong & Rattanaphanee, 2011). Lactic acid can be separated and substantially purified from fermentation broths by several membrane-based unit operations as shown in the Fig. 4.

7. Conclusions

Due to the growing demand of l(+) lactic acid for a wide range of applications in addition with the production of biodegradable plastic (PLA), it is necessary to make improvement in the conventional fermentation-based lactic acid production processes with efficient and sustainable method. Membrane based hybrid reactor system have proved successful in this goal without generating any negative environmental crash (Fig. 4). The lactic acid production is significantly influenced by fermentation time, temperature and substrate levels. Lactic acid bacteria, regarded generally as safe, that produce lactic acid optimal under conditions at 30 °C and pH 5 in the customized MRS broth containing 2% yeast extract and 2% glucose (Adesokan, Odetoyinbo, & Okanlawon, 2009). Similarly, Biswas (2005) has also reported that under controlled pH condition, there is a significant increase in the level of production of lactic acid when compared to uncontrolled conditions. Recently, lignocellulosic materials have received a great attention as possible feed stocks to substitute the edible starch material. Low cost cellulosic materials such as industrial wastes, agricultural waste and forestry waste are recommended as cost effective feed stocks for large scale fermentation (Tang, Bu, Deng, Zhu, & Jiang, 2012). The separation and purification of lactic acid from the fermentation broth are major components of the production expenditure (Matsumoto, Panigrahi, Murakami, & Kondo, 2011). However, there is still a big need for the researches to be carried out in order to produce lactic acid biotechnologically and commercially within the lowest cost, lowering the cost of the raw materials and improvement of high-performance microorganisms producing lactic acid (Vijayakumar et al., 2008).

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