Description:FIELD OF THE INVENTION
[0001] The present disclosure relates to a system and method for efficiently producing organic acid. Particularly, the present disclosure provides a method of production of an organic acid by integrated fermentation and adsorption system. More particularly, the present disclosure provides a method of production of lactic acid by integrated fermentation and adsorption system.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Lactic acid (LA) has widespread commercial applications in the food industry and is a building block for the most widely used biodegradable polymer, polylactic acid (PLA). The edible grade 88% LA is used as an acidulant in almost major food and beverage. Lactic Acid is generally produced through the biochemical route of microbial fermentation of carbohydrates and sugars such as glucose, maltose, lactose, or sucrose, derived from feedstocks such as dairy, beet sugar, molasses, whey, and barley malt. It can also be produced using the starch present in the grains such as wheat and rice, etc.
[0004] The demand for lactic acid is increasing at a considerable rate due to its wide range of applications. However, high cost of the raw materials, e.g., starch and refined sugars, has significant contribution towards production cost and represents one of the most severe obstacles for the fermentative production of lactic acid to compete with chemical synthesis. Lactic acid production can be made more economical by switching to cheaper feedstock like agri-waste (lignocellulosic biomass). Lignocellulosic biomass is considered a promising feedstock for lactic acid production due to its abundant availability and it is a sustainable resource. Ultimately, sugars from either 1G feedstock or 2G feedstock can be utilised to produce LA via fermentation route.
[0005] Sugars are derived from starch-based crops such as corn, wheat, rice etc. by enzymatic hydrolysis. However, lignocellulosic biomass is more complicated and requires additional pretreatment method before enzymatic hydrolysis can be done. In case the pretreatment is acidic, then H2SO4 is generally used. Similarly, for the enzymatic hydrolysis of the starchy 1st generation biomass, sulphuric acid is used for the pH adjustment. The usage of Sulphuric acid releases sulphate ions in the solution which is an impurity. This is dealt with in the downstream processing.
[0006] The downstream processing of lactic acid is one of the major bottlenecks in the industrial production of lactic acid, and approximately 40-70% of the operating and capital costs are due to the separation process. The generation of lactic acid during fermentation results in a decrease of pH, which is detrimental to the growth of microbial strains used for LA fermentation. In industrially employed methods, generally, calcium hydroxide is added to the fermentation broth to maintain the pH, which results in the formation of calcium lactate. LA is recovered by the precipitation method wherein the fermentation broth is acidified using sulfuric acid to convert calcium lactate to LA resulting in solid waste gypsum. Thus, alternative LA separation technologies such as adsorption have been investigated that do not yield salt waste. Adsorption by ion exchange resins is widely employed for bio-separation, and different ion exchangers such as poly(4-vinyl pyridine) resin (PVP), IRA-420, IRA-400 are reported for selective adsorption of lactic acid from the complex mixture of fermentation broth. The advantages include simplicity in operation, low energy consumption and high selectivity. It leads to a high LA yield with minimum waste generation.
[0007] Boonmee et al. [Arab J Sci Eng., 2016, 41, 2067–2075] discloses extractive fermentation with 155.8 g/L initial glucose and 364 g of anion exchange resin yielded a 1.2-fold increase in total lactate produced and a 5.9-fold increase in productivity compared with standard batch fermentation at the same glucose concentration. The addition of resin also served as a pH control strategy. Elution of the resin-bound lactate using 1 M HCl at 0.1 bed volume/min resulted in complete recovery of lactate.
[0008] CN111574360A discloses a method for separating lactic acid, which comprises the following steps: (1) carrying out ion exchange on the lactic acid-containing solution to obtain a lactic acid solution; (2) carrying out reduced pressure concentration on the lactic acid solution to obtain a lactic acid concentrated solution; (3) performing molecular distillation on the lactic acid concentrated solution to obtain refined lactic acid; wherein, in the lactic acid-containing solution, the content of lactic acid is 5-30 wt%.
[0009] The literature describes the usage of ion exchange resins during fermentation for adsorption of lactic acid which results in the reduction of low value salts. However, the current literature does not focus on the presence of sulphate ions in the broth. These sulphate ions if not removed from the system will get adsorbed on the resin during fermentation and will become an impurity in the further purification. Thus, there is a need to develop a new method for efficient production of lactic acid with higher purity.

OBJECTS OF THE INVENTION
[0010] An objective of the present disclosure is to provide a method of production of an organic acid by integrated fermentation and adsorption system.
[0011] Another objective of the present disclosure is to provide a method of production of lactic acid by integrated fermentation and adsorption system.
[0012] Another objective of the present disclosure is to provide a simple method with reduced number of steps for lactic acid production with enhanced recovery, high purity and minimum waste generation.
[0013] Still another objective of the present disclosure is to provide a method of production of lactic acid without sulphate impurities.
[0014] Yet another objective of the present disclosure is to provide a method of production of lactic acid with pH control strategy that reduces impurities and low value products’ generation.

SUMMARY OF THE INVENTION
[0015] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0016] The present disclosure relates to a system and method for efficiently producing organic acid. Particularly, the present disclosure provides a method of production of an organic acid by integrated fermentation and adsorption system. More particularly, the present disclosure provides a method of production of lactic acid by integrated fermentation and adsorption system.
[0017] An aspect of the present disclosure is to provide a method of production of an organic acid by integrated fermentation and adsorption system comprising: a) pre-treating a biomass with one or more reagent to obtain a pretreated biomass; b) contacting the pretreated biomass of step a) with a neutralising reagent to neutralise the sulphate or chloride impurities and to obtain a suspension; c) initiating hydrolysis under condition using a hydrolysis reagent and continuing with fermentation with addition of one or more microbe and followed by maintaining pH via pH loop consisting of an ion-exchange resin column(s) and a solid liquid separation unit; d) processing by continuation fermentation till sugars are completely utilized by microbe and to obtain ion-exchange resin column(s) containing adsorbed organic acid; e) contacting the ion-exchanged resin column(s) of step d) with a base solution to desorb the organic acid solution; f) passing the desorbed organic acid solution of step e) through activated carbon bed and then filters to obtain a treated solution; and g) passing the treated solution of step f) through a cation exchange resin column to obtain a pure organic acid stream followed by concentration to obtain the desired concentration.
[0018] Another aspect of the present disclosure is to provide a method of production of lactic acid by integrated fermentation and adsorption system comprising: a) pre-treating a biomass with one or more reagent to obtain a pretreated biomass; b) contacting the pretreated biomass of step a) with a neutralising reagent to neutralise the sulphate or chloride impurities and to obtain a suspension; c) initiating hydrolysis under condition using a hydrolysis reagent and continuing with fermentation with addition of Lactic Acid Bacteria (LAB) and followed by maintaining pH via pH loop consisting of an ion-exchange resin column(s) and a solid liquid separation unit; d) processing by fermentation till sugars are completely utilized by microbe and to obtain ion-exchange resin column(s) containing adsorbed lactic acid; e) contacting the ion-exchanged resin column(s) of step d) with a base solution to desorb the lactic acid solution; f) passing the desorbed lactic acid solution of step e) through activated carbon bed and then filters to obtain a treated solution; and g) passing the treated solution of step f) through a cation exchange resin column to obtain a pure lactic acid stream followed by concentration to obtain the desired concentration.
[0019] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0021] Figure 1: Schematic for Integrated Fermentation and Adsorption for Lactic Acid Production.

DETAILED DESCRIPTION OF THE INVENTION
[0022] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0023] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0024] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0025] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0026] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it is individually recited herein.
[0027] All processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0028] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0029] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0030] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0031] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description that follows, and the embodiments described herein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0032] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0033] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0034] The present disclosure provides a method for the production of an organic acid. More particularly, the present disclosure provides a method for the production of lactic acid by separate or one-pot hydrolysis and fermentation wherein the pH of the system is maintained by in-situ removal of lactic acid via adsorption. The process involves the removal of sulphate or chloride impurities and does not require the addition of base during fermentation, thereby simplifying the downstream processing. Weak base anion exchange resin has been selected for the present invention because it is more selective towards the adsorption of lactic acid. The elution is done by sodium hydroxide, which results in the formation of sodium lactate. Sodium lactate is then acidified using strong cation exchange resin to obtain lactic acid.
[0035] The sulphates or chlorides were adsorbed by the resin instead of the lactic acid during in-situ fermentation that lead to decreased purity and lesser recovery of lactic acid. However, the present disclosure is on the premise of a surprising discovery that addition of calcium hydroxide and using lactic acid for pH modulation in the process, resulted in higher recovery of the lactic acid with higher purity. The observed results are unexpected and surprising.
[0036] An embodiment of the present disclosure provides a method of production of an organic acid by integrated fermentation and adsorption system comprising: a) pre-treating a biomass with one or more reagent to obtain a pretreated biomass; b) contacting the pretreated biomass of step a) with a neutralising reagent to neutralise the sulphate or chloride impurities and to obtain a suspension; c) initiating hydrolysis under condition using a hydrolysis reagent and continuing with fermentation with addition of one or more microbe and followed by maintaining pH via pH loop consisting of an ion-exchange resin column(s) and a solid liquid separation unit; d) processing by fermentation till sugars are completely utilized by microbe and to obtain ion-exchange resin column(s) containing adsorbed organic acid; e) contacting the ion-exchanged resin column(s) of step d) with a base solution to desorb the organic acid solution; f) passing the desorbed organic acid solution of step e) through activated carbon bed and then filters to obtain a treated solution; and g) passing the treated solution of step f) through a cation exchange resin column to obtain a pure organic acid stream followed by concentration to obtain the desired concentration.
[0037] In an embodiment, the organic acid is selected from but not limited to a group consisting of lactic acid, citric acid and succinic acid.
[0038] In an embodiment, the microbes is selected from a group consisting of acid producing bacteria or yeast and combination thereof.
[0039] Another embodiment of the present disclosure provides a method of production of lactic acid by integrated fermentation and adsorption system comprising: a) pre-treating a biomass with one or more reagent to obtain a pretreated biomass; b) contacting the pretreated biomass of step a) with a neutralising reagent to neutralise the sulphate or chloride impurities and to obtain a suspension; c) initiating hydrolysis under condition using a hydrolysis reagent and continuing with fermentation with addition of Lactic Acid Bacteria (LAB) and followed by maintaining pH via pH loop consisting of an ion-exchange resin column(s) and a solid liquid separation unit; d) processing by fermentation till sugars are completely utilized by microbe and to obtain ion-exchange resin column(s) containing adsorbed lactic acid; e) contacting the ion-exchanged resin column(s) of step d) with a base solution to desorb the lactic acid solution; f) passing the desorbed lactic acid solution of step e) through activated carbon bed and then filters to obtain a treated solution; and g) passing the treated solution of step f) through a cation exchange resin column to obtain a pure lactic acid stream followed by concentration to obtain the desired concentration.
[0040] In an embodiment, the biomass is selected from a group consisting of but not limited to cellulose, hemi-cellulose, rice grain, wheat grain, rice straw, rice husk, wheat straw, wheat husk, bagasse, molasses and combination thereof.
[0041] In an embodiment, the reagent in step a) is selected from but not limited to a group consisting of sulphuric acid, sulphurous acid, hydrochloric acid, alpha amylase enzyme, lactic acid, glucoamylase enzyme, sodium hydroxide, magnesium hydroxide, potassium hydroxide, ammonium hydroxide, water, ethanol, acetic acid, formic acid and combination thereof.
[0042] In an embodiment, the neutralising reagent in step b) is selected from but not limited to a group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonium hydroxide, magnesium hydroxide, lactic acid, succinic acid, citric acid, water and combination thereof. The pH is conditioned to 6-9. Preferably, the pH is set at 7. For acid treated, the pH will be increased from 2 to 7. For base treated, the pH will be reduced from 13 to 7.
[0043] In an embodiment, the condition for fermenting the biomass using LAB in step c) includes temperature in the range of 30-40 °C for a period of 48 to 120 hrs with agitation at a speed in the range of 100 to 300 rpm. Preferably, the temperature is 37 °C and at a speed of 250 rpm.
[0044] In an embodiment, the hydrolysis in step c) is selected from separate hydrolysis and fermentation (SHF) and hybrid hydrolysis and fermentation (HHF).
[0045] In an embodiment, the hydrolysis reagent in step c) for hydrolysis is an enzyme complex composed of but not limited to glucoamylase, cellulase, ß-glucosidase, xylanase, endoglucanase, cellobiohydrolase and combination thereof.
[0046] In an embodiment, the SHF in step c) includes addition of enzyme complex of 3-15 FPU/g biomass or 0.4-1.2 mg/kg biomass for hydrolysis at a temperature ranging from 30 – 60 °C and separation of the hydrolysate after 24-48 hrs and then addition of microbes to the hydrolysate for fermentation.
[0047] In an embodiment, the HHF in step c) includes addition of enzyme complex of 3-15 FPU/g biomass or 0.4-1.2 mg/kg biomass for hydrolysis at a temperature ranging from 30 – 60 °C and addition of microbes for fermentation in the same reaction vessel after 4 to 24 hrs of hydrolysis.
[0048] In an embodiment, the SHF includes hydrolysis for a period in the range of 4 to 72 hrs and fermentation for a period in the range of 4 to 72 hrs.
[0049] In an embodiment, the HHF includes hydrolysis and fermentation for a period in the range of 24 to 72 hrs.
[0050] In an embodiment, the pH conditioning during hydrolysis consists of decreasing the pH from 8±1 to 5±0.5 by adding lactic acid for lignocellulosic biomass.
[0051] In an embodiment, the pH conditioning during hydrolysis consists of lowering the pH from 7±1 to 6±1 for cooked grains biomass by using lactic acid.
[0052] In an embodiment, the pH control at the start of the fermentation in step (d) for SHF consists of adding a neutralising reagent or circulating the fermentation broth through ion-exchange resin column to maintain the pH within the range of 5±0.5 to 6±0.5. During the fermentation, the pH control consists of circulating the fermentation broth either through solid liquid separation unit and ion-exchange resin column or directly through ion-exchange resin columns to maintain the pH within the range of 5±0.5 to 6±0.5.
[0053] In an embodiment, the pH control at the start of the fermentation in step (d) for HHF consists of adding a neutralising reagent or circulating the fermentation broth through solid liquid separation unit and ion-exchange resin column to maintain the pH within the range of 5±0.5 to 6±0.5. During the fermentation, the pH control consists of circulating the fermentation broth through solid liquid separation unit and ion-exchange resin column to maintain the pH within the range of 5±0.5 to 6±0.5.
[0054] In an embodiment, the neutralising reagent in step (d) is selected from a group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonium hydroxide, magnesium hydroxide and combination thereof.
[0055] In an embodiment, the solid-liquid separation unit consists of but not limited to a group of centrifuge, cyclones, filters, decanters, sieve shakers, sedimentation vessels and combination thereof.
[0056] In an embodiment, the base in step e) is selected from but not limited to a group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide and combination thereof. Preferably, the base is 1N sodium hydroxide.
[0057] In an embodiment, the anion exchange resin is selected from weak anion exchange resin. The weakly basic anion exchange resin is selected from but not limited to polyalkylamine groups attached to styrene and divinylbenzene copolymer. In some embodiment, the anion exchange resin is selected from a group consisting of but not limited to resins supplied by Cytiva, Dowex, Purolite, AmberLite, Indion, and combination thereof.
[0058] In an embodiment, the cation exchange resin is selected from strong cation exchange resin. The strongly acidic cation exchange resin is selected from but not limited to sulfonic acid groups attached to styrene and divinylbenzene copolymer. In some embodiment, the cation exchange resin is selected from a group consisting of but not limited to resins supplied by Cytiva, Dowex, Purolite, AmberLite, Indion, and combination thereof.
[0059] In an embodiment, the present disclosure provides a method for production of lactic acid from biomass by integrated fermentation and adsorption system comprising of a fermenter connected to solid liquid separation unit and one or more columns packed with anion exchange resin, with continuous circulation of fermentation broth through the column/columns for maintaining the pH of the fermentation broth. Further, the downstream processing steps involve the desorption of lactic acid from the ion exchange column and is done by base such as sodium hydroxide. Further, the decolorization of the above solution is carried out by passing through a bed of activated charcoal. The activated charcoal is removed by filtration and then the acidification of the solution is carried out by passing through cation exchange resin to obtain the pure lactic acid (Figure 1).
[0060] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
EXAMPLES
[0061] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
Comparative Example 1: LA production from Rice Straw by SHF
[0062] The biomass was pretreated with 1 M sulfuric acid in a reactor. The pretreated slurry was subjected to solid-liquid separation to separate the liquid containing C5 sugars (xylose). The solids were then mixed with water to achieve a loading of 7.5 % (w/v). The pH of the resultant suspension was increased from 2 to 5 using Ca(OH)2. Post this, the solution is transferred to a fermenter/reactor and sterilised. After sterilisation, enzymatic hydrolysis was carried out at 50 oC using cellulase enzyme complex for 72 h. The residual solids in the hydrolysate were removed by centrifugation. The sugar concentration in the liquid hydrolysate was then analysed by HPLC.
[0063] Post separation, the hydrolysate was fed into a fermenter and the fermentation was initiated by addition of inoculum at 37 ?C under aseptic condition. Fermentation was then carried out at 37 oC at 250 rpm agitation. The pH of the media was maintained at 6.5 by the use of pH loop consisting of the ion-exchange column and the solid liquid separation unit. Samples were collected at regular intervals until the glucose was almost completely utilised by the microbe. The sugar concentration was analysed by HPLC. When the fermentation was completed, the pH was increased to 7 by circulation of the entire broth through the pH circuit. The ion-exchange columns were then processed for downstream separation of LA as described in Example – 4.
Example 1: LA production from Rice grain by SHF
[0064] The grain was treated with 1 M sulfuric acid and alpha amylase enzyme in a reactor at a pH of 6.5, temperature of 90 oC for 2 hours with a solid loading of 35 % (w/w). Then the temperature of the reactor was reduced to 60 oC and pH was decreased to 5 using lactic acid and glucoamylase enzyme was added to the solution. The conditions were maintained for 16 hours. Then the slurry was subjected to solid-liquid separation to separate the liquid containing C6 sugars (glucose). The pH of the solution containing sugars was increased from 5 to 7 using Ca(OH)2 during which the sulphate impurities in the pretreated biomass were precipitated out. The pH of the suspension was then decreased to 6.5 by using lactic acid and subsequently sterilised for fermentation.
[0065] Post sterilisation, the fermentation was initiated by addition of inoculum at 37 ?C under aseptic condition. The fermenter agitator was kept at 250 rpm and the temperature of the fermenter was set at 37 oC. The pH of the media was maintained at 6.5 by the use of pH loop consisting of the ion-exchange column and the solid liquid separation unit. Samples were collected at regular intervals until the glucose was almost completely utilised by the microbe. The sugar concentration was analysed by HPLC. Though LA fermentation is an anaerobic fermentation, no nitrogen was purged in the fermenter to reduce the operating cost of industrial fermentation. After 48 h, when the fermentation was complete, the pH was increased to 7 by circulation of the entire broth through the pH circuit. The ion-exchange columns were then processed for downstream separation of LA as described in Example-4. The recovery of the lactic acid based on the sugars present in the fermentation broth was in the range of 70-90% and the purity of Lactic Acid was greater than 90%.The result of Example 1 indicates higher recovery of lactic acid with higher purity.
Example 2: LA production from Rice Straw by SHF
[0066] The biomass was pretreated with 1 M sulfuric acid in a reactor. The pretreated slurry was subjected to solid-liquid separation to separate the liquid containing C5 sugars (xylose). The solids were then mixed with water to achieve a loading of 7.5 % (w/v). The pH of the resultant suspension was increased from 2 to 7 using Ca(OH)2 during which the sulphate impurities in the pretreated biomass were precipitated out. The pH of the suspension was further decreased to 5 by using lactic acid and then the solution is transferred to a fermenter/reactor and sterilised. After sterilisation, enzymatic hydrolysis was carried out at 50 oC using cellulase enzyme complex for 72 h. The residual solids in the hydrolysate were removed by centrifugation. The sugar concentration in the liquid hydrolysate was then analysed by HPLC.
[0067] Post separation, the hydrolysate was fed into a fermenter and the fermentation was initiated by addition of inoculum at 37 ?C under aseptic condition. The pH of the solution was increased to 6.5 by addition of Ca(OH)2. Fermentation was then carried out at 37 oC at 250 rpm agitation. The pH of the media was maintained at 6.5 by the use of pH loop consisting of the ion-exchange column and the solid liquid separation unit. Samples were collected at regular intervals until the glucose was almost completely utilised by the microbe. The sugar concentration was analysed by HPLC. Though LAB fermentation is an anaerobic fermentation, no nitrogen was purged in the fermenter to reduce the operating cost of industrial fermentation. After 48 h, when the fermentation was complete, the pH was increased to 7 by circulation of the entire broth through the pH circuit. The ion-exchange columns were then processed for downstream separation of LA as described in Example-4. The recovery of the lactic acid based on the sugars present in the fermentation broth was in the range of 60-85% and the purity of Lactic Acid was greater than 90%. The result of Example 2 indicates higher recovery of lactic acid with higher purity.
Example 3: LA production from Rice Straw by Hybrid Hydrolysis & Fermentation (HHF)
[0068] The pretreated lignocellulosic biomass was fed into fermenter and pH was adjusted from 2 to7 by addition of Ca(OH)2 followed by reduction of pH to 5 using lactic acid. The temperature was maintained at 50 ?C. Hydrolysis was initiated by the addition of cellulase enzyme complex. Fermentation was started after 24 h of enzymatic hydrolysis by aseptic addition of the Lactic Acid Bacteria (LAB).The pH of the fermentation media was maintained at 5.0 using pH loop consisting of the ion-exchange column and the solid liquid separation unit. Samples were collected at regular intervals to analyse the sugar and other metabolites by HPLC. After 36 hours of LAB addition, the pH was increased to 7 by circulation of the entire broth through the pH circuit. The ion-exchange columns were then processed for downstream separation of LA as described in Example 4. The recovery of the lactic acid was in the range of 50-85%.
Example 4: Downstream Processing of LA from fermentation broth
[0069] The ion exchange resin columns of Comparative Example-1, Example-1, Example-2 & Example-3 which contain the adsorbed Lactic Acid are first treated with 1 M NaOH solution to desorb the lactic acid. This desorbed solution is then passed through activated carbon bed and then through the filters. The treated solution is then passed through cation exchange resin column. The resultant mixture is then concentrated, and pure lactic acid is obtained. The recovery of the lactic acid from the resin was greater than 90-95%.
[0070] Comparatively, the sulphates were reduced by >12% and the yield of LA increased by >21%.
Lactic Acid (g/L) Sulphates (g/L)
Example-2 (Present invention) 16.98 1.66
Comparative Example-1 14.03 1.87
[0071] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

ADVANTAGES OF THE INVENTION
[0072] The recovery of the sugars in the hydrolysis is also better with the present strategy. Novel pH control strategy during hydrolysis of acid pretreated biomass wherein the sulphate or chloride impurities are neutralised with neutralising reagent as defined above preferably calcium hydroxide. The sulphate or chloride impurities if present will decrease the efficiency of ion-exchange column during in-situ adsorption. Additionally, the problem of sulphate or chloride impurities in the product is also solved in the present invention.
[0073] The pH control strategy of using the target product organic acid leads to reduced contamination issues compared to conventional mineral acids.
[0074] In industrially employed methods, generally calcium hydroxide is added to the fermentation broth to maintain the pH which results in formation of calcium lactate. LA is recovered by precipitation method wherein the fermentation broth is acidified using sulfuric acid to convert calcium lactate to LA resulting in solid waste gypsum for which disposal is an issue. Further, removal of gypsum from the LA containing fermentation broth requires an energy intensive process of vacuum filtration and evaporation. In present invention, the pH control during fermentation is by in-situ adsorption of acid and hence, there is no generation of gypsum which is an advantage of the present invention.
[0075] Reduced number of process steps and better purity of final product compared to precipitation method.
[0076] There is no requirement of addition of base during fermentation, thus reduced operating expenditure & capital expenditure.
[0077] The inhibitory effects of certain chemicals that are released during fermentation of lignocellulosic biomass are prevented by simultaneous adsorption.
[0078] The present invention provided higher recovery of lactic acid with higher purity.
, Claims:1. A method of production of an organic acid by integrated fermentation and adsorption system comprising:
a) pre-treating a biomass with one or more reagent to obtain a pretreated biomass;
b) contacting the pretreated biomass of step a) with a neutralising reagent to neutralise the sulphate or chloride impurities and to obtain a suspension;
c) initiating hydrolysis under condition using a hydrolysis reagent and continuing with fermentation with addition of one or more microbes and followed by maintaining pH via pH loop consisting of an ion-exchange resin column(s) and a solid liquid separation unit;
d) processing by continuation fermentation till sugars are completely utilized by microbes and to obtain ion-exchange resin column(s) containing adsorbed organic acid;
e) contacting the ion-exchanged resin column(s) of step d) with a base solution to desorb the organic acid solution;
f) passing the desorbed organic acid solution of step e) through activated carbon bed and then filters to obtain a treated solution; and
g) passing the treated solution of step f) through a cation exchange resin column to obtain a pure organic acid stream followed by concentration to obtain the desired concentration.
2. The method as claimed in claim 1, wherein the organic acid is selected from a group consisting of lactic acid, citric acid and succinic acid.
3. The method as claimed in claim 1, wherein the microbes is selected from a group consisting of acid producing bacteria or yeast and combination thereof.
4. The method as claimed in claim 1, wherein the method of production of lactic acid by integrated fermentation and adsorption system comprising:
a) pre-treating a biomass with one or more reagent to obtain a pretreated biomass;
b) contacting the pretreated biomass of step a) with a neutralising reagent to neutralise the sulphate or chloride impurities and to obtain a suspension;
c) initiating hydrolysis under condition using a hydrolysis reagent and continuing with fermentation with addition of Lactic Acid Bacteria (LAB) and followed by maintaining pH via pH loop consisting of an ion-exchange resin column(s) and a solid liquid separation unit;
d) processing by fermentation till sugars are completely utilized by microbe and to obtain ion-exchange resin column(s) containing adsorbed lactic acid;
e) contacting the ion-exchanged resin column(s) of step d) with a base solution to desorb the lactic acid solution;
f) passing the desorbed lactic acid solution of step e) through activated carbon bed and then filters to obtain a treated solution; and
g) passing the treated solution of step f) through a cation exchange resin column to obtain a pure lactic acid stream followed by concentration to obtain the desired concentration.
5. The method as claimed in claim 1, wherein the biomass is selected from a group consisting of cellulose, hemi-cellulose, rice grain, wheat grain, rice straw, rice husk, wheat straw, wheat husk, bagasse, molasses and combination thereof.
6. The method as claimed in claim 1, wherein the reagent in step a) is selected from a group consisting of sulphuric acid, sulphurous acid, hydrochloric acid, alpha amylase enzyme, lactic acid, glucoamylase enzyme, sodium hydroxide, magnesium hydroxide, potassium hydroxide, ammonium hydroxide, water, ethanol, acetic acid, formic acid and combination thereof.
7. The method as claimed in claim 1, wherein the neutralising reagent in step b) is selected from a group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonium hydroxide, magnesium hydroxide, lactic acid, succinic acid, citric acid, water and combination thereof.
8. The method as claimed in claim 1, wherein the condition for fermenting the biomass using microbe in step c) includes temperature in the range of 30-40 °C for a period of 48 to 120 hrs with agitation at a speed in the range of 200 to 300 rpm.
9. The method as claimed in claim 1, wherein the hydrolysis in step c) is selected from separate hydrolysis and fermentation (SHF) and hybrid hydrolysis and fermentation (HHF).
10. The method as claimed in claim 1, wherein the hydrolysis reagent in step c) for hydrolysis is an enzyme complex composed of glucoamylase, cellulase, ß-glucosidase, xylanase, endoglucanase, cellobiohydrolase and combination thereof.
11. The method as claimed in claim 9, wherein the SHF in step c) includes addition of enzyme complex of 3-15 FPU/g biomass or 0.4-1.2 mg/kg biomass for hydrolysis at a temperature ranging from 30 – 60 °C and separation of the hydrolysate after 24-48 hrs and then addition of microbes to the hydrolysate for fermentation.
12. The method as claimed in claim 9, wherein the HHF in step c) includes addition of enzyme complex of 3-15 FPU/g biomass or 0.4-1.2 mg/kg biomass for hydrolysis at a temperature ranging from 30 – 60 °C and addition of microbes for fermentation after 4 to 24 hrs.
13. The method as claimed in claim 9, wherein the SHF includes hydrolysis for a period in the range of 4 to 72 hrs and fermentation for a period in the range of 4 to 72 hrs.
14. The method as claimed in claim 9, wherein the HHF includes hydrolysis and fermentation for a period in the range of 24 to 72 hrs.
15. The method as claimed in claim 9, wherein the pH condition during hydrolysis consists of decreasing the pH from 8±1 to 5±0.5 by adding lactic acid for lignocellulosic biomass.
16. The method as claimed in claim 9, wherein the pH condition during hydrolysis consists of lowering the pH from 7±1 to 6±1 for cooked grains biomass by using lactic acid.
17. The method as claimed in claim 9, wherein the pH control during fermentation for SHF consists of circulating the fermentation broth either through solid liquid separation unit and ion-exchange resin column or directly through ion-exchange resin columns to maintain the pH within the range of 5±0.5 to 6±0.5.
18. The method as claimed in claim 9, wherein the pH control during fermentation for HHF consists of circulating the fermentation broth through solid liquid separation unit and ion-exchange resin column or directly through to maintain the pH within the range of 5±0.5 to 6±0.5.
19. The method as claimed in claim 9, wherein the solid-liquid separation unit consists of a group of centrifuge, cyclones, filters, decanters, sieve shakers, sedimentation vessels and combination thereof.
20. The method as claimed in claim 1, wherein the base in step e) is selected from a group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide and combination thereof.
21. The method as claimed in claim 1, wherein the anion exchange resin is selected from weak anion exchange resin.
22. The method as claimed in claim 1, wherein the cation exchange resin is selected from strong cation exchange resin.