Description:FIELD OF THE INVENTION
[0001] The present disclosure relates to convert the lignocellulosic material to useful product. Particularly, the present disclosure provides a method for production of sugars from a lignocellulosic biomass material.

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] WO2016169892A1 discloses a process for the preparation of a sugar product from lignocellulosic material comprising the step of: a) hydrolysing the lignocellulosic material enzymatically in one or more containers using an enzyme composition to obtain enzymatically hydrolysed lignocellulosic material, and b) optionally, recovering the enzymatically hydrolysed lignocellulosic material, wherein at least one of the containers has a volume of at least 1 m3 and wherein the enzymatic hydrolysis is carried out in the presence of a succinate buffer. The recycling is done with the enzymatic hydrolysis broth itself in WO2016169892A1.
[0004] WO2009150455A2 discloses the method comprising separating biomass derived waste, reducing the biomass to a substantially liquid form, enzymatically reducing the biomass substances therein using an enzyme mix chosen to maximize output from the waste material and fermenting the reduced mix to produce specific outputs from the waste material. A selected specific output material is extracted from the liquid for subsequent purification and processing, water and remaining solids are separated so that the water may be recycled or flushed and the solids may be composted, compressed for further use or put to landfill. The invention also considers specific biowaste categories for processing and converting and the adaptation of the apparatus to specific environments.
[0005] Lyu et al. [Bioresource Technology, 2019, 290, 121756] discloses that the addition of acids could effectively catalyze the hydrolysis of hemicellulose to C5 sugars and contribute to the subsequent enzymatic hydrolysis of cellulose. It was found that all three organic acids promote xylose production, and the copresence of AA?+?LA could limit the content of the fermentation inhibitor. The optimum proportion of three organic acids were 0.33?wt% AA?+?0.45?wt% LA?+?0.20?wt% FA, and the yield of C5 sugars after pretreatment and C6 sugar after enzymatic hydrolysis were 89.06% and 78.56%, respectively. The kinetic studies proved that byproduct-organic acids could promote xylose production and inhibit its further degradation and explained that xylose would accumulate at lower temperatures.
[0006] Dai et al. [Process Biochemistry, 2015, 50 (11), 1951-1957] discloses effects of sugars and solvents on phase separation and 2,3-butanediol distribution were investigated to obtain an appropriate sugaring-out extraction system. The system consisting of t-butanol/glucose/water was chosen to obtain the operation conditions according to 2,3-butanediol distribution and recovery, including glucose addition, 2,3-butanediol concentration and (NH4)2HPO4 concentration. The glucose-rich bottom phase was reused for fermentation of 2,3-butanediol after removing the solvent. When the fermentation broth (60.3 g/L 2,3-butanediol) was mixed with 30% (w/v) glucose, 1.8% (w/v) (NH4)2HPO4 and equal volume of t-butanol, 76.3% 2,3-butanediol was distributed into the top phase and 80.4% glucose into the bottom phase, and 78.0% soluble proteins and 86.8% lactic acid were separated from 2,3-butanediol. When the bottom phase was diluted to prepare fermentation medium, glucose consumption and 2,3-butanediol production were similar to those using freshly prepared normal fermentation medium. Sugaring-out extraction is a novel alternative separation for bio-based chemicals.
[0007] KR101544188B1 discloses a biomass pretreatment using an organic acid and recovering the used organic acid by electrodialysis and using the recovered organic acid for biomass pretreatment technology.
[0008] WO2016207147A1 discloses a process for preparing succinic acid from lignocellulosic material by enzymatic hydrolysis and fermentation. The process comprises a step of subjecting the enzymatically hydrolysed lignocellulosic material to a detoxification step by contacting the material with activated carbon.
[0009] Biochemicals have widespread commercial applications and have the potential to replace crude oil-based chemicals that have a detrimental effect on the environment. Lactic Acid (LA), Succinic Acid (SA) and Citric Acid (CA) are organic acids and all have widespread usage in the food and pharmaceutical industry. They are primarily used as acidity regulators, taste enhancers in almost all major food and beverages and are also used extensively in the pharmaceutical sector also. For sustainability, all these organic acids can be produced through the biochemical route of microbial fermentation of carbohydrates and sugars. Thus, maximum recovery of sugars will significantly improve the yield of the process and also improve its economics. These sugars can be sourced from Lignocellulosic biomass (LCB) which is available in abundance.
[0010] LCB contains both Cellulose and Hemicellulose which yield C6 & C5 sugars respectively. The recovery of sugars from LCB (2G) is generally done via enzymatic hydrolysis. The enzymatic hydrolysis process uses enzymes (bio-catalyst) and these enzymes are substrate, temperature and pH specific. Enzymes are very specific to pH and have a narrow working range. Since 2G biomass is hygroscopic, it adsorbs acid/alkali during its pre-treatment, which are released during hydrolysis. This disturbs the pH and accordingly reduces the efficacy of the enzyme due to which the time of hydrolysis is increased. To counter this effect, buffers can be added, but they are an additional cost to the process. In case the buffers are not used, then the released acid/alkali will increase/decrease the pH of the process and decrease the enzyme efficiency leading to increased process time and lower product yield.
[0011] The C6 & C5 sugars are further utilised by the organisms to produce the biochemicals such as organic acids. However, not all strains can utilise both C5 or C6 types of the sugars to produce the organic acids. In most cases, either only C6 is utilised or only C5 is utilised. The unutilised sugars are generally discarded which is a loss. However, these sugars can be utilised to produce other biochemicals such as, xylose & xylitol can be obtained from C5 sugars. Thus, rendering flexibility to the process.
[0012] During the downstream processing of the organic acids, wastewater is generated in the process that contains residual products such as sugars, acids. These unutilised sugars pass through the downstream processing section and if this water is directly sent to the treatment plant, then these useful recoverable products would be washed out of the system.
[0013] Thus, there is a need to develop a novel low-cost method to counter the above issues that utilizes effluent stream to increase the sugar recovery and simultaneously improve the yield of organic acids with reduced water footprint and time.

OBJECTS OF THE INVENTION
[0014] An object of the present invention is to provide a method for production of sugars from a lignocellulosic biomass material.
[0015] Another object of the present invention is to provide a method for production of sugars that utilizes the target produced organic acid as a buffer in the process.
[0016] Still another object of the present invention is to provide a novel method that utilizes effluent stream to increase the sugar recovery and simultaneously improve the yield of organic acids with reduced water footprint and time.
[0017] Yet another object of the present invention is to reduce the operating cost, capital cost and environmental impact of the process.

SUMMARY OF THE INVENTION
[0018] 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.
[0019] An aspect of the present disclosure is to provide a method for production of sugars from a lignocellulosic biomass material comprising: a) pre-treating 5 to 20% w/v of the lignocellulosic biomass material with 0.1-20% w/v of one or more reagent to obtain a pretreated slurry; b) subjecting the pretreated slurry to solid-liquid separation to separate a liquid stream and a solid residue; c) adjusting the pH of the solid residue from step b) using a neutralising stream to obtain a slurry; d) hydrolysing 5-20 % w/v of the slurry from step c) in a fermenter/reactor using enyzme (2-15 FPU/g of biomass) and a buffer to obtain sugars; e) processing-by fermentation of the sugars to produce an organic acid in the fermentation broth; f) downstream-processing of the fermentation broth to produce organic acid and an effluent stream containing residual sugars, organic acid & its conjugate salt; and g) recycling the effluent stream of step f) in step a) or step c) or step d).
[0020] 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
[0021] The following drawings form part of the present specification and are included to further illustrate aspects of the present invention. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0022] Figure 1 illustrates a schematic for enhanced sugar recovery by sugar enrichment & buffered enzymatic hydrolysis.

DETAILED DESCRIPTION OF THE INVENTION
[0023] 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.
[0024] 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.”
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] The present disclosure provides a novel method for the production of reducing sugars from lignocellulosic biomass materials (Figure 1). The process involves using the effluent streams of the downstream process containing reducing sugars and salts. This process not only reduces the water footprint of the process but also increases recovery of the sugars. The effluent stream containing the target product salts, is used to generate a buffer for the pH range specific to the enzyme which, increases the efficiency of the enzyme. Additionally, the effluent stream sugars are further concentrated which aids in recovery of the sugar reducing the water footprint of the process. Thus, this strategy increases the process efficiency and simultaneously reduces its environmental footprint through recycling. Moreover, this novel method has widespread application and can be used in the production of organic acids such as lactic acid (LA), succinic acid (SA) and citric acid (CA).
[0036] An embodiment of the present disclosure provides a method for production of sugars from a lignocellulosic biomass material comprising: a) pre-treating 5 to 20% w/v of the lignocellulosic biomass material with 0.1-20% w/v of one or more reagent to obtain a pretreated slurry; b) subjecting the pretreated slurry to solid-liquid separation to separate a liquid stream and a solid residue; c) adjusting the pH of the solid residue from step b) using a neutralising stream to obtain a slurry; d) hydrolysing 5-20 % w/v of the slurry from step c) in a fermenter/reactor using enyzme (2-15 FPU/g of biomass) and a buffer to obtain sugars; e) processing by fermentation of the sugars to produce an organic acid in the fermentation broth; f) downstream-processing of the fermentation broth to produce organic acid and an effluent stream containing residual sugars, organic acid & its conjugate salt; and g) recycling the effluent stream of step f) in step a) or step c) or step d).
[0037] In an embodiment, the lignocellulosic biomass material is selected from a group consisting of but not limited to cellulose, hemi-cellulose, rice straw, rice husk, wheat straw, wheat husk, bagasse, molasses, soya straw and combination thereof.
[0038] In an embodiment, the reagent in step a) for pretreatment is selected from a group consisting of but not limited to sulphuric acid, sulphurous acid, hydrochloric acid, lactic acid, sodium hydroxide, magnesium hydroxide, potassium hydroxide, ammonium hydroxide, water, ethanol, acetic acid, formic acid and combination thereof.
[0039] In an embodiment, the solid-liquid separation unit in step b) is selected from a group consisting of centrifuge, cyclones, filters, decanters, sieve shakers, sedimentation vessels and combination thereof.
[0040] In an embodiment, the neutralizing stream in step c) for maintaining pH is selected from a group consisting of sulphuric acid, nitric acid, hydrochloric acid, lactic acid, succinic acid, citric acid, sodium hydroxide, calcium hydroxide, ammonium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, sodium lactate, calcium lactate, potassium lactate, sodium succinate, calcium succinate, potassium succinate, sodium citrate, calcium citrate, potassium citrate, water and combination thereof.
[0041] In an embodiment, the method further comprises an effluent stream of the downstream processing which is mixed with step c) or step d) or step a).
[0042] In an embodiment, the effluent stream contains 0.1 to 10 % w/v of C5 sugars or C6 sugars, lactic acid, succinic acid, citric acid, lactic acid salt, succinic acid salt, citric acid salt and combination thereof.
[0043] In an embodiment, the liquid stream in step b) is C5 sugars, C6 sugars, lignin and combination thereof.
[0044] In an embodiment, the C5 sugar is xylose, arabinose and combination thereof. The C6 sugar is glucose, mannose, and combination thereof. The effluent stream of the downstream processing is utilized for enrichment of the sugars and preparation of the buffer to reduce the water footprint of the entire process.
[0045] In an embodiment, the buffer is selected from the target product organic acid in the process.
[0046] In an embodiment, the buffer in step d) for maintaining pH is selected from a group consisting of lactic acid, succinic acid, citric acid, sodium hydroxide, calcium hydroxide, ammonium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate in varying conc. of 0.1-10 %w/v and combination thereof to maintain a pH in the range of 4 to 6.
[0047] In an embodiment, the enzymatic hydrolysis in step d) is selected from Separate Hydrolysis (SH) or Hybrid Hydrolysis & Fermentation (HHF) for lignocellulosic biomass. The enzymatic hydrolysis is carried out for a period of 2 to 72 hrs in SH. The enzymatic hydrolysis and fermentation is carried out simultaneously for a period in the range of 24 to 72 hrs in HHF.
[0048] In an embodiment, the enzyme used in step d) is composed of but not limited to glucoamylase, cellulase, ß-glucosidase, xylanase, endoglucanase, cellobiohydrolase and combination thereof. The enzyme complex is added in the range of 2 to 15 FPU/g biomass for hydrolysis.
[0049] In an embodiment, the enzymatic hydrolysis in step d) is carried out at a temperature in the range of 40 to 60 °C for a period in the range of 2 to 120 hrs. Preferably, at a temperature of 50 °C for a period in the range of 2 to 72 hrs.
[0050] In an embodiment, the fermentation in step e) comprises transferring the slurry in the fermenter under aseptic condition followed by increasing the pH in the range of 6 to 7, preferably pH of 6.5 by addition of alkali and fermentation is carried out at a temperature in the range of 35-40 °C, preferably at 37 °C for a period of 24 to 50 hrs, preferably 48 hrs.
[0051] In an embodiment, the alkali is selected from a group consisting of sodium hydroxide, calcium hydroxide, ammonium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate and combination thereof.
[0052] In an embodiment, the downstream processing is selected from a group consisting of adsorption, esterification-hydrolysis, precipitation, membrane separation, electrodialysis and combination thereof. The residual organic acid and the residual salt is recycled in the process.
[0053] In an embodiment, the method further comprises of separating the concentrated sugars from the downstream processing effluent stream and is diverted for production of biochemical.
[0054] 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
[0055] 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: Hydrolysis of Rice Straw
[0056] The biomass was pretreated with 1 M sulphuric acid in a reactor. The pretreated slurry was subjected to solid-liquid separation. The solids were then mixed with water and the pH of the resultant suspension was increased to 5 using Ca(OH)2. Then the slurry (5-10% solids) was transferred to a fermenter/reactor and sterilised. After sterilisation, enzymatic hydrolysis was carried out at 50 °C using enzyme complex for 24-72 h. The sugar concentration in the liquid hydrolysate was then analysed by HPLC.
[0057] The fermentation of the hydrolysed slurry 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 ?C at 250 rpm agitation. The pH of the media was maintained at 6.5 by the use of pH loop. After 48 h, when the fermentation was complete, the fermentation broth was subjected to adsorption with ion-exchange columns for downstream separation of LA.
Example 1: Hydrolysis of Rice Straw using recycled Lactic Acid stream
[0058] The effluent stream of the anion-exchange downstream process from comparative example 1 was mixed with acid pre-treated biomass. The pH of the resultant suspension was increased to 5 using Ca(OH)2. Then lactic acid buffer was added to the solution to maintain pH 5. Then the slurry (5-10% solids) was transferred to a fermenter/reactor and sterilised. After sterilisation, enzymatic hydrolysis was carried out at 50°C using enzyme complex for 24-72 h. The sugar concentration in the liquid hydrolysate was then analysed by HPLC. The concentration of C5 sugar post enzymatic hydrolysis was increased by >40%and the total sugars increased by >13% as compared to initial.
Example 2: Hydrolysis of Rice Straw using Lactic Acid buffer
[0059] The biomass was pretreated with 1 M sulphuric 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 and the pH of the resultant suspension was increased to 5 using Ca(OH)2. Then lactic acid buffer was added to the solution to maintain pH at 5. Then the slurry (5-10% solids) was transferred to a fermenter/reactor and sterilised. After sterilisation, enzymatic hydrolysis was carried out at 50 °C using enzyme complex for 24-72 h. The sugar concentration in the liquid hydrolysate was then analysed by HPLC.
[0060] A relatively better yield (>20%) of sugars was obtained as compared to non-buffer hydrolysis.
Example 3: Hydrolysis of Rice Straw using Succinic Acid Buffer
[0061] The biomass was pretreated with 1 M sulphuric 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 and the pH of the resultant suspension was increased to 5 using Ca(OH)2. Then succinic acid buffer was added to the solution to maintain pH at 5. Then the slurry (5-10% solids) was transferred to a fermenter/reactor and sterilised. After sterilisation, enzymatic hydrolysis was carried out at 50 °C using enzyme complex for 24-72 h. The sugar concentration in the liquid hydrolysate was then analysed by HPLC. The yield of sugars obtained was more than 15% higher compared to non-buffer hydrolysis.

Example 4: Hydrolysis of Rice Straw using Citric Acid Buffer
[0062] The biomass was pretreated with 1 M sulphuric 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 and the pH of the resultant suspension was increased to 5 using Ca(OH)2. Then Citric acid buffer was added to the solution to maintain pH at 5. Then the slurry (5-10% solids)was transferred to a fermenter/reactor and sterilised. After sterilisation, enzymatic hydrolysis was carried out at 50°C using enzyme complex for 24-72 h. The sugar concentration in the liquid hydrolysate was then analysed by HPLC.
[0063] The sugar yields obtained was more than 19% higher as compared to non-buffer hydrolysis.
Example 5: Hydrolysis of Wheat Straw using Lactic Acid buffer
[0064] The biomass was pretreated with 1 M sulphuric 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 and the pH of the resultant suspension was increased to 5 using Ca(OH)2. Then lactic acid buffer was added to the solution to maintain pH 5. Then the slurry (5-10% solids)was transferred to a fermenter/reactor and sterilised. After sterilisation, enzymatic hydrolysis was carried out at 50°C using enzyme complex for 24-72 h. The sugar concentration in the liquid hydrolysate was then analysed by HPLC.
[0065] Better yield (>15%) of sugars was obtained as compared to non-buffer hydrolysis.
Experiment Hydrolysis Sugar Yield(g/L)
Glucose Xylose
Comparative Example 1 29.86 4.11
Example 1 (present invention) 30.44 7.85

[0066] 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 PRESENT INVENTION
[0067] The method of the present invention utilizes the downstream processing effluent stream containing residual sugars and recycles them in the system. This recycling method helps in increasing the concentration of the residual sugars significantly. After continuous recycling and increasing the sugar concentration to a certain level, the stream in whole or part can be sent for recovery of the concentrated sugars. Thus, sugar recovery can be increased many fold.
[0068] For further enhancement of the sugar recovery, the current novel method utilizes the target product organic acid (LA or SA or CA) to create a buffer system that improves the efficiency of the hydrolysis process. The target product buffer can be separated and recovered in the downstream process post fermentation of the sugars. This ensures no impurity is introduced in the system that would increase the downstream processing cost.
[0069] The present invention also improves the organic acid yield of the process by recycling the residual organic acid or its conjugate salt back to the hydrolysis or pretreatment section instead of sending it to the wastewater treatment zone to further reduce the water footprint.
[0070] These novel steps ensure better yield and recovery of the sugars and the final product with reduced water footprint.
[0071] These steps reduce the operating cost, capital cost and environmental impact of the process.
, Claims:1. A method for production of sugars from a lignocellulosic biomass material comprising:
a) pre-treating 5 to 20% w/v of the lignocellulosic biomass material with 0.1-20% w/v of one or more reagent to obtain a pretreated slurry;
b) subjecting the pretreated slurry to solid-liquid separation to separate a liquid stream and a solid residue;
c) adjusting the pH of the solid residue from step b) using a neutralising stream to obtain a slurry;
d) hydrolysing 5-20 % w/v of the slurry from step c) in a fermenter/reactor using enyzme (2-15 FPU/g of biomass) and a buffer to obtain sugars;
e) processing by fermentation of the sugars to produce an organic acid in the fermentation broth;
f) downstream-processing of the fermentation broth to produce organic acid and an effluent stream containing residual sugars, organic acid & its conjugate salt; and
g) recycling the effluent stream of step f) in step a) or step c) or step d).
2. The method as claimed in claim 1, wherein the lignocellulosic biomass material is selected from a group consisting of but not limited to cellulose, hemi-cellulose, rice straw, rice husk, wheat straw, wheat husk, bagasse, molasses, soya straw and combination thereof.
3. The method as claimed in claim 1, wherein the reagent in step a) for pretreatment is selected from a group consisting of but not limited to sulphuric acid, sulphurous acid, hydrochloric acid, lactic acid, sodium hydroxide, magnesium hydroxide, potassium hydroxide, ammonium hydroxide, water, ethanol, acetic acid, formic acid and combination thereof.
4. The method as claimed in claim 1, wherein the solid-liquid separation unit in step b) is selected from a group consisting of centrifuge, cyclones, filters, decanters, sieve shakers, sedimentation vessels and combination thereof.
5. The method as claimed in claim 1, wherein the neutralizing stream in step c) for maintaining pH is selected from a group consisting of sulphuric acid, nitric acid, hydrochloric acid, lactic acid, succinic acid, citric acid, sodium hydroxide, calcium hydroxide, ammonium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, sodium lactate, calcium lactate, potassium lactate, sodium succinate, calcium succinate, potassium succinate, sodium citrate, calcium citrate, potassium citrate, water and combination thereof.
6. The method as claimed in claim 1, wherein the method further comprises an effluent stream of the downstream processing which is mixed with step c) or step d) or step a).
7. The method as claimed in claim 6, wherein the effluent stream contains 0.1 to 10 % w/v of C5 sugars, C6 sugars, lactic acid, succinic acid, citric acid, lactic acid salt, succinic acid salt, citric acid salt and combination thereof.
8. The method as claimed in claim 1, wherein the liquid stream in step b) is C5 sugars, C6 sugars, lignin and combination thereof.
9. The method as claimed in claim 8, wherein the C5 sugar is xylose, arabinose and combination.
10. The method as claimed in claim 1, wherein the buffer is selected from the target product organic acid in the process.
11. The method as claimed in claim 1, wherein the buffer in step d) for maintaining pH is selected from a group consisting of lactic acid, succinic acid, citric acid, sodium hydroxide, calcium hydroxide, ammonium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate in varying conc. of 0.1-10 % w/v and combination thereof to maintain the pH in the range of 4 to 6.
12. The method as claimed in claim 1, wherein the enzymatic hydrolysis in step d) is selected from Separate Hydrolysis (SH) or Hybrid Hydrolysis & Fermentation (HHF) for lignocellulosic biomass.
13. The method as claimed in claim 12, wherein the enzymatic hydrolysis is carried out for a period of 2 to 72 hrs in SH.
14. The method as claimed in claim 12, wherein the enzymatic hydrolysis and fermentation is carried out simultaneously for a period in the range of 24 to 72 hrs in HHF.
15. The method as claimed in claim 1, wherein the enzyme used in step d) is composed of but not limited to glycoamylase, cellulase, ß-glucosidase, xylanase, endoglucanase, cellobiohydrolase and combination thereof.
16. The method as claimed in claim 1, wherein the enzymatic hydrolysis in step d) is carried out at a temperature in the range of 40 to 60 °C for a period in the range of 2 to 120 hrs.
17. The method as claimed in claim 1, wherein the fermentation in step e) comprises transferring the slurry in the fermenter under aseptic condition followed by increasing the pH in the range of 6 to 7 by addition of an alkali and fermentation is carried out at a temperature in the range of 35-40 °C for a period of 24 to 72 hrs.
18. The method as claimed in claim 17, wherein the alkali is selected from a group consisting of sodium hydroxide, calcium hydroxide, ammonium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate and combination thereof.
19. The method as claimed in claim 1, wherein the downstream processing is selected from a group consisting of adsorption, esterification-hydrolysis, precipitation, membrane separation, electrodialysis and combination thereof.
20. The method as claimed in claim 1, wherein the method further comprises of separating the concentrated sugars from the downstream processing effluent stream and is diverted for production of biochemical.