Claims:1. A process for de-polymerization of lignocellulosic biomass, the process comprising the steps of:
taking the lignocellulosic biomass having size ranging from 1 mm to 50 mm;
contacting the lignocellulosic biomass with an aqueous metal catalyst solution to obtain a hydrolysate stream;
subjecting the hydrolysate stream to solid liquid separation to obtain a first liquid stream and a first solid stream; and
segregating solids and the metal catalyst from said first liquid stream.
2. The process as claimed in claim 1, wherein the aqueous metal catalyst solution comprises a mixture of a metal salt and a mineral acid.
3. The process as claimed in claim 2, wherein the metal salt is magnesium chloride, and wherein the mineral acid is selected from nitric acid, sulfuric acid, hydrochloric acid and mixtures thereof.
4. The process as claimed in claim 1, wherein the aqueous metal catalyst solution comprises an aqueous solution of: magnesium chloride having strength ranging from 1.5 M to 4.0 M, and a mineral acid in an amount ranging from 0.1% to 1.5 % w/v.
5. The process as claimed in claim 1, wherein the lignocellulosic biomass is contacted with the aqueous metal catalyst solution such that solid to liquid ratio ranges from 1:5 to 1:10.
6. The process as claimed in claim 1, wherein the step of contacting the lignocellulosic biomass with an aqueous metal catalyst solution comprises:
mixing the lignocellulosic biomass with the aqueous metal catalyst solution to form a premix, said premix having a solid to liquid ratio ranging from 1:5 to 1:10; and
subjecting said premix to an elevated temperature for a time period ranging from 1 hour to 5 hours under a stirring condition to obtain the hydrolysate stream.
7. The process as claimed in claim 6, wherein the premix is subjected to the elevated temperature ranging from 80°C to 120°C under stirring condition for a time period ranging from 1 hour to 5 hours in a first reactor to obtain the hydrolysate stream.
8. The process as claimed in claim 1, wherein the step of contacting the lignocellulosic biomass with an aqueous metal catalyst solution comprises:
mixing the lignocellulosic biomass with the aqueous metal catalyst solution to form a premix, said premix having a solid to liquid ratio ranging from 1:5 to 1:10;
subjecting said premix to an elevated temperature ranging from 80°C to 120°C for a time period ranging from 1 hour to 5 hours under stirring condition in a first reactor to obtain a slurry; and
contacting the slurry with a solid catalyst at a temperature ranging from 80°C to 120°C for a time period ranging from 20 minutes to 120 minutes under stirring condition in a second reactor to obtain the hydrolysate stream.
9. The process as claimed in claim 8, wherein the solid catalyst is selected from acid phosphates, acid resins, functional group-modified sulfonates, active protonated agents, lattice decrystalizing agents and mixtures thereof.
10. The process as claimed in claim 8, wherein the step of segregating solids and the metal catalyst from said first liquid stream includes subjecting the first liquid stream to any or a combination of: nano-filtration and column chromatography.
11. The process as claimed in claim 1, wherein the process comprises the steps of:
contacting the first solid stream with a catalyst to effect hydrolysis thereof;
subjecting the hydrolysate to solid liquid separation to obtain a second liquid stream and a second solid stream; and
segregating fermentable sugars and the catalyst from said second liquid stream.
12. In an embodiment, the catalyst is selected from the group including: (a) the metal catalyst segregated from the first liquid stream; (b) a solid catalyst selected from acid phosphate, acid resin, functional group-modified sulfonates, active protonated agents, lattice decrystalizing agents and mixtures thereof; (c) a bio-catalytic protein; and (d) combinations of the metal catalyst segregated from the first liquid stream, the solid catalyst and the bio-catalytic protein.

, Description:TECHNICAL FIELD
[0001] The present disclosure pertains to the technical field of production of biofuels. In particular, the present disclosure relates to a process for de-polymerization of lignocellulosic biomass.

BACKGROUND
[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] Lignocellulosic biomass (such as rice/wheat straw, corn cobs, sugarcane bagasse, agricultural residues, forestry wastes etc.) is one of the most abundant and relatively cheaper feedstock available in the world, and can be used for the production of sugars, alcohols, metabolites, proteins and the likes. However, the commercial use of biomass for such processes is limited by the inherent structure of lignocellulose, which is recalcitrant in nature, leading to the requirement of energy intensive operations for the disruption of such lignocellulosic biomass.
[0004] Lignocellulosic biomass is composed of cellulose, hemicellulose and lignin linked to each other via extensive covalent and hydrogen bonds. The de-polymerisation of polymeric sugars like cellulose or hemicellulose into their corresponding mono-saccharides is the first step in conversion of biomass to biofuels or other high value metabolites. In order to produce fermentable sugars, the biomass has to be subjected to a series of steps including size reduction (pre-processing), pre-treatment (typically a thermochemical process) and saccharification (a biochemical process). Saccharification is the rate limiting step and is conventionally carried out by using the mixture of cellulolytic enzymes (endo-cellulase, exo-cellulase and ß-glucosidases), which are difficult to produce, and hence, they need to be procured from commercial suppliers at a high cost. As a result, most of the existing processes available for biomass conversion are complex, time consuming and require high capital expenditure (CAPEX) and operational expenditure (OPEX). Therefore, it is important to develop an economically viable and sustainable process for production of fermentable sugars from biomass.
[0005] There is, therefore, a long standing need in the art of an economical and commercially viable process for de-polymerization of lignocellulosic biomass. The present disclosure fulfils the existing needs, at least in part, and provides an improved process for de-polymerization of lignocellulosic biomass.
[0006] 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.

OBJECTS
[0007] An object of the present disclosure is to arrive at a process for de-polymerization of lignocellulosic biomass that is economical.
[0008] An object of the present disclosure is to arrive at a process for de-polymerization of lignocellulosic biomass that affords reduction in both capital expenditure and operating expenditure.
[0009] Another object of the present disclosure is to arrive at a process for de-polymerization of lignocellulosic biomass that precludes the need of subjecting the lignocellulosic biomass to costly and energy intensive pre-treatment for deconstruction or dissolution of complex lignocellulose or carbohydrates.
[0010] Further object of the present disclosure is to arrive at a process for de-polymerization of lignocellulosic biomass that affords production of fermentable sugars reducing the need of enzyme (biocatalyst) dosage as compared to the conventional processes and with minimal production of inhibitors.
[0011] Still further object of the present disclosure is to arrive at a process for de-polymerization of lignocellulosic biomass that affords utilization of multiple lignocellulosic feedstock/biomass.
SUMMARY
[0012] The present disclosure pertains to the technical field of production of biofuels. In particular, the present disclosure relates to a process for de-polymerization of lignocellulosic biomass.
[0013] An aspect of the present disclosure relates to a process for de-polymerization of lignocellulosic biomass, the process including the steps of: (a) taking the lignocellulosic biomass having size ranging from 1 mm to 50 mm; (b) contacting the lignocellulosic biomass with an aqueous metal catalyst solution to obtain a hydrolysate stream; (c) subjecting the hydrolysate stream to solid liquid separation to obtain a first liquid stream and a first solid stream; and (d) segregating solids and the metal catalyst from said first liquid stream.
[0014] In an embodiment, the aqueous metal catalyst solution comprises a mixture of a metal salt and a mineral acid. In an embodiment, the metal salt is magnesium chloride. In an embodiment, the mineral acid is selected from nitric acid, sulfuric acid, hydrochloric acid and mixtures thereof. In an embodiment, the aqueous metal catalyst solution comprises an aqueous solution of: magnesium chloride having strength ranging from 1.5 M to 4.0 M, and a mineral acid in an amount ranging from 0.1% to 1.5 % w/v. In an embodiment, the lignocellulosic biomass is contacted with the aqueous metal catalyst solution such that solid to liquid ratio ranges from 1:5 to 1:10.
[0015] In an embodiment, the step of contacting the lignocellulosic biomass with an aqueous metal catalyst solution comprises: (i) mixing the lignocellulosic biomass with the aqueous metal catalyst solution to form a premix, said premix having a solid to liquid ratio ranging from 1:5 to 1:10; and (ii) subjecting said premix to an elevated temperature for a time period ranging from 1 hour to 5 hours under a stirring condition to obtain the hydrolysate stream.
[0016] In an embodiment, the premix is subjected to the elevated temperature ranging from 80°C to 120°C under stirring condition for a time period ranging from 1 hour to 5 hours in a first reactor to obtain the hydrolysate stream.
[0017] In an embodiment, the step of contacting the lignocellulosic biomass with an aqueous metal catalyst solution comprises: (i) mixing the lignocellulosic biomass with the aqueous metal catalyst solution to form a premix, said premix having a solid to liquid ratio ranging from 1:5 to 1:10; (ii) subjecting said premix to an elevated temperature ranging from 80°C to 120°C for a time period ranging from 1 hour to 5 hours under stirring condition in a first reactor to obtain a slurry; and (iii) contacting the slurry with a solid catalyst at a temperature ranging from 80°C to 120°C for a time period ranging from 20 minutes to 120 minutes under stirring condition in a second reactor to obtain the hydrolysate stream. In an embodiment, the solid catalyst is selected from acid phosphates, acid resins, functional group-modified sulfonates, active protonated agents, lattice decrystalizing agents and mixtures thereof.
[0018] In an embodiment, the step of segregating solids and the metal catalyst from said first liquid stream includes subjecting the first liquid stream to any or a combination of: nano-filtration and column chromatography.
[0019] In an embodiment, the process further includes the steps of: contacting the first solid stream and the solids with a catalyst to effect hydrolysis thereof; subjecting the hydrolysate to solid liquid separation to obtain a second liquid stream having fermentable sugars and a second solid stream. In an embodiment, the catalyst is selected from the group including: (a) the metal catalyst segregated from the first liquid stream; (b) a solid catalyst selected from BPO4, Amberlyst-120 H, Functional group-modified sulfonates, Active Protonated agents, Lattice decrystalizing agents and mixtures thereof; (c) a bio-catalyst; and (d) combinations of the metal catalyst segregated from the first liquid stream, the solid catalyst and the bio-catalyst.
[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 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.
[0022] FIG. 1A and 1B illustrate an exemplary schematic showing a process for de-polymerization of lignocellulosic biomass in accordance with an embodiment of the present disclosure.
[0023] FIG. 2 illustrates an exemplary schematic showing a process for de-polymerization of lignocellulosic biomass in accordance with another embodiment of the present disclosure.
[0024] FIG. 3 illustrates an exemplary graph showing results obtained from DNS assay upon de-polymerization of lignocellulosic biomass (rice straw and sugarcane baggasse), in accordance with an embodiment of the present disclosure.
[0025] FIG. 4A and 4B illustrate exemplary graphs showing results obtained from DNS assay upon de-polymerization of lignocellulosic biomass (rice straw and sugarcane baggasse), in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0026] The following is a detailed description of embodiments of the present invention. The embodiments are in such detail as to clearly communicate the invention. 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 invention as defined by the appended claims.
[0027] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0028] 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.
[0029] 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.”
[0030] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0031] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0032] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, 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.
[0033] 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 were individually recited herein.
[0034] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0035] All methods 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.
[0036] 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.
[0037] 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.
[0038] The present disclosure pertains to the technical field of production of biofuels. In particular, the present disclosure relates to a process for de-polymerization of lignocellulosic biomass.
[0039] An aspect of the present disclosure relates to a process for de-polymerization of lignocellulosic biomass, the process including the steps of: (a) taking the lignocellulosic biomass having size ranging from 1 mm to 50 mm; (b) contacting the lignocellulosic biomass with an aqueous metal catalyst solution to obtain a hydrolysate stream; (c) subjecting the hydrolysate stream to solid liquid separation to obtain a first liquid stream and a first solid stream; and (d) segregating solids and the metal catalyst from said first liquid stream.
[0040] In an embodiment, the lignocellulosic biomass is subjected to pre-processing (as known conventionally) before subjecting it to the advantageous process of the present disclosure. In an embodiment, the lignocellulosic biomass (also referred to herein alternatively and synonymously as “feedstock biomass”) is subjected to size reduction such that the lignocellulosic biomass is of size ranging from 1 mm to 50 mm, preferably, between 5 mm to 30 mm, and most preferably between 7 mm to 15 mm.
[0041] In an embodiment, the aqueous metal catalyst solution comprises a mixture of a metal salt and a mineral acid. In an embodiment, the metal salt is magnesium chloride. In an embodiment, the mineral acid is selected from nitric acid, sulfuric acid, hydrochloric acid and mixtures thereof. In an embodiment, the aqueous metal catalyst solution comprises an aqueous solution of: magnesium chloride having strength ranging from 1.5 M to 4.0 M, and a mineral acid in an amount ranging from 0.1% to 1.5 % w/v. In an embodiment, the aqueous metal catalyst solution comprises an aqueous solution of: magnesium chloride having strength ranging from 2.5 M to 3.5 M, and a mineral acid in an amount ranging from 0.1% to 1.5 % w/v. In an embodiment, the lignocellulosic biomass is contacted with the aqueous metal catalyst solution such that solid to liquid ratio ranges from 1:5 to 1:10.
[0042] In an embodiment, the step of contacting the lignocellulosic biomass with an aqueous metal catalyst solution comprises: (i) mixing the lignocellulosic biomass with the aqueous metal catalyst solution to form a premix, said premix having a solid to liquid ratio ranging from 1:5 to 1:10; (ii) subjecting said premix to an elevated temperature ranging from 80°C to 120°C for a time period ranging from 1 hour to 5 hours under stirring condition in a first reactor to obtain a slurry; and (iii) contacting the slurry with a solid catalyst at a temperature ranging from 80°C to 120°C for a time period ranging from 20 minutes to 120 minutes under stirring condition in a second reactor to obtain the hydrolysate stream. In an embodiment, the solid catalyst is selected from acid phosphates, acid resins, functional group-modified sulfonates, active protonated agents, lattice decrystalizing agents and mixtures thereof. Non-limiting examples of acid phosphates include BPO4, H3PO4, H4P2O7, H5P3O10, H6P4O13, P2O10 and the likes. Non-limiting examples of acid resins include Amberlyst-15, Amberlyst-15 (wet), IR-118 (H+), IR-120 (H+), Amberlyst-XN 1010 and the likes. Non-limiting examples of functional group-modified sulfonates include CH3SO2OH, C2H5SO2OH, CH3C6H4SO3H (pTsOH) and the likes. Non-limiting examples of active protonated agents include H3O+, Fe(H2O)63+, HSO4–, H2PO4– and the likes. Non-limiting examples of lattice recrystallizing agents include CuSO4·5H2O, CuSO4·3H2O, MgCl2.6H2O, Na2SO4.10H2O, ZnCl2.6H2O, CaCl2·6H2O, ZnNO3·6H2O, Na2SO4·10H2O, LiClO3·3H2O, K2HPO4·6H2O, KF·4H2O, FeCl3·6H2O and the likes.
[0043] In an embodiment, the process further includes the steps of: contacting the first solid stream and the solids with a catalyst to effect hydrolysis thereof; and subjecting the hydrolysate to solid liquid separation to obtain a second liquid stream having fermentable sugars and a second solid stream. In an embodiment, the catalyst is selected from the group including: (a) the metal catalyst segregated from the first liquid stream; (b) a solid catalyst selected from acid phosphates, acid resins, functional group-modified sulfonates, active protonated agents, lattice decrystalizing agents and mixtures thereof; (c) a bio-catalyst; and (d) combinations of the metal catalyst segregated from the first liquid stream, the solid catalyst and the bio-catalyst. In an embodiment, the catalyst is a bio-catalyst.
[0044] In an embodiment, the step of segregating solids and the metal catalyst from said first liquid stream includes subjecting the first liquid stream to any or a combination of: nano-filtration and column chromatography.
[0045] FIG. 1A illustrates an exemplary schematic showing various steps involved in the process for de-polymerization of lignocellulosic biomass in accordance with an embodiment of the present disclosure. As can be seen from FIG. 1, the lignocellulosic biomass of appropriate size (102) is mixed with at least a part of the aqueous metal catalyst solution (104a) using a mixer (106), such as a counter-current mixer, to form the premix (108). The premix (108) can then be introduced in the first reactor (110), where the premix (108) can further be mixed with the aqueous metal catalyst solution (104b) such that the final premix has a solid to liquid (S/L) ratio ranging from 1:5 to 1:10. Alternatively, the lignocellulosic biomass (102) can directly be mixed with the aqueous metal catalyst solution (104) in the first reactor (110). The premix (108) is then subjected to the elevated temperature ranging from 80°C to 120°C for a time period ranging from 1 hour to 5 hours under stirring condition (e.g. at a speed of 300 to 500 RPM) to effect hydrolysis of the lignocellulosic biomass. The partly hydrolyzed lignocellulosic biomass (112) (referred to herein synonymously and alternatively as “slurry”) can be conveyed to a second reactor (120), wherein it can be mixed with the solid catalyst (114) and subjected to the temperature ranging from 80°C to 120°C for a time period ranging from 20 minutes to 120 minutes under stirring condition (e.g. at a speed of 300 to 500 RPM) to obtain the hydrolysate stream (116). The hydrolysate stream (116) is then subjected to the solid liquid separation in a separator (130) to obtain a first liquid stream (118) and a first solid stream (122). Any conventional solid liquid separator such as filter press or such other filtration assembly, as known to or appreciated by persons skilled in the art may be used. The first liquid stream (118) can then be subjected to nano-filtration (e.g. using NF membrane with cut-off of 100-300 g/mol) and/or column chromatography employing specific resins known conventionally (generally shown as 140) to segregate solids (125), metal catalyst (104) and fermentable sugars (135). The metal catalyst (104) can then again be reused (either directly or after regeneration thereof) and mixed with another batch of lignocellulosic biomass to effect hydrolysis thereof.
[0046] As can be seen from FIG. 1B, the first solid stream (122) and the and solids (125) are mixed with a catalyst (124), such as a biocatalyst, in a third reactor (150) to effect hydrolysis of the lignocellulosic biomass resulting in generation of a hydrolysate (126). The hydrolysis in the third reactor (150) may be effected at a temperature ranging from 50°C to 200°C and at a pH ranging from 1.0 to 7.0. The hydrolysate (126) is then subjected to solid liquid separation in a separator (160) to obtain a second liquid stream having fermentable sugars (128) and a second solid stream (130). The second solid stream (130) may be rejected/discarded. The fermentable sugars (135 and 128) so obtained, which typically includes glucose, xylose and arabinose, may be subjected to fermentation to produce bio-fuels such as ethanol.
[0047] In another embodiment, the step of contacting the lignocellulosic biomass with an aqueous metal catalyst solution comprises: (i) mixing the lignocellulosic biomass with the aqueous metal catalyst solution to form a premix, said premix having a solid to liquid ratio ranging from 1:5 to 1:10; and (ii) subjecting said premix to an elevated temperature for a time period ranging from 1 hour to 5 hours under a stirring condition to obtain the hydrolysate stream. In an embodiment, the premix is subjected to the elevated temperature ranging from 80°C to 120°C under stirring condition for a time period ranging from 1 hour to 5 hours in a first reactor to obtain the hydrolysate stream.
[0048] In an embodiment, the process further includes the steps of: contacting the first solid stream and the solids with a catalyst to effect hydrolysis thereof; and subjecting the hydrolysate to solid liquid separation to obtain a second liquid stream having fermentable sugars and a second solid stream. In an embodiment, the catalyst is selected from the group including: (a) the metal catalyst segregated from the first liquid stream; (b) a solid catalyst selected from acid phosphates, acid resins, functional group-modified sulfonates, active protonated agents, lattice decrystalizing agents and mixtures thereof; (c) a bio-catalyst; and (d) combinations of the metal catalyst segregated from the first liquid stream, the solid catalyst and the bio-catalyst. In an embodiment, the catalyst is a biocatalyst. In an embodiment, the step of segregating solids and the metal catalyst from said first liquid stream includes subjecting the first liquid stream to any or a combination of: nano-filtration and column chromatography.
[0049] FIG. 2 illustrates an exemplary schematic showing various steps in the process for de-polymerization of lignocellulosic biomass in accordance with an embodiment of the present disclosure. As can be seen from FIG. 2, the lignocellulosic biomass of appropriate size (202) is mixed with at least a part of the aqueous metal catalyst solution (204a) using a mixer (206), such as a counter-current mixer, to form the premix (208). The premix (208) can then be introduced in the first reactor (210), where the premix (208) can further be mixed with the aqueous metal catalyst solution (204b) such that the final premix has a solid to liquid (S/L) ratio ranging from 1:5 to 1:10. Alternatively, the lignocellulosic biomass (202) can directly be mixed with the aqueous metal catalyst solution (204) in the first reactor (210) such that the premix has a solid to liquid (S/L) ratio ranging from 1:5 to 1:10. The premix (208) is then subjected to the elevated temperature ranging from 80°C to 120°C for a time period ranging from 1 hour to 5 hours, preferably, for about 2 hours, under stirring condition (e.g. at a speed of 300 to 500 RPM) to effect hydrolysis of the lignocellulosic biomass generating a hydrolysate stream (216). The hydrolysate stream (216) is then subjected to the solid liquid separation in a separator (230) to obtain a first liquid stream (218) and a first solid stream (222). Any conventional solid liquid separator such as filter press or such other filtration assembly, as known to or appreciated by persons skilled in the art may be used. The first liquid stream (218) can then be subjected to nano-filtration (e.g. using NF membrane with cut-off of 100-300 g/mol) and/or column chromatography employing specific resins known conventionally (generally shown as 240), to segregate solids (225) and the metal catalyst (204). The metal catalyst (204) can again be reused (either directly or after regeneration thereof) and mixed with another batch of lignocellulosic biomass to effect hydrolysis thereof. The first solid stream (222) and the solids (225) are mixed with a catalyst (224), such as a biocatalyst, in a second reactor (250) to effect hydrolysis of the lignocellulosic biomass that may be present in the solid streams (222 and 225) resulting in generation of a hydrolysate (226). The hydrolysis in the second reactor (250) may be effected at a temperature ranging from 40°C to 60°C and at a pH ranging from 3.0 to 6.0. The hydrolysate (226) is then subjected to solid liquid separation in a separator (260) to obtain a second liquid stream having fermentable sugars (228) and a second solid stream (230). The second solid stream (230) may be rejected/discarded. The fermentable sugars (228) so obtained, which typically includes glucose, xylose and arabinose, may be subjected to fermentation to produce bio-fuels such as ethanol.
[0050] While the foregoing description discloses various embodiments of the disclosure, other and further embodiments of the invention may be devised without departing from the basic scope of the disclosure. 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
[0051] Lignocellulosic biomass and pre-processing thereof
[0052] Raw materials (cellulose, lignocellulosic material, and starchy materials) were procured from local market. Before subjecting them to hydrolysis, the lignocellulosic materials (rice straw and sugarcane bagasse) were size reduced to ~10mm length using biomass shredder and analyzed for its chemical composition (provided below in Table 1). The moisture content of the size reduced biomass was ~10 % wt. The commercial cellulose and starch grains (powdered) were directly used for hydrolysis to produce fermentable sugars.
Table 1: Compositions of Lignocellulosic biomass
Component Rice straw
Con. (% wt.) Sugarcane bagasse
Con. (% wt.)
Glucan 29.5 32
Xylan 15.4 16.1
Arabinan 3.8 2.8
ASL 4.1 3.1
AIL 14.5 16.8
Extractives 12.5 5.2
Ash (Inorganic) 9.2 3.8
Moisture 10 12

[0053] De-polymerization of the lignocellulosic biomass
[0054] The pre-processed substrates (2 g dry weight) prepared above were transferred to Teflon screw capped pressure tubes (100 mL capacity). Then, 20 mL of catalyst solution (3 M MgCl2 + 1.5 % w/v of HNO3) was added thereto. The solid to liquid ratio in the start of the hydrolysis reaction was maintained at 1: 10. To keep the contents in motion, magnetic bead was added to each of the reaction tubes. The hydrolysis reaction was carried at 100°C for 2 h, at mixing speed of 500 RPM to obtain the slurry.
[0055] The slurry was then mixed with 0.5 % Wt. of BPO4 at 120°C for 1 h under stirring conditions (500 RPM) to obtain the hydrolysate stream. The pH of the reaction mixture was acidic (~1.5). After completion of hydrolysis, 10 mL of extra water (ambient temperature) was added to dissolve the released sugars. The produced sugars were then determined with standard method of DNS assay.
[0056] The hydrolysate stream was then filtered to afford solid liquid separation. The liquid stream (first liquid stream) was then subjected to nano-filtration using NF membrane with cut-off of 200 g/mol to separate metal catalyst, fermentable sugars and solids.
[0057] The solids from the filtration unit and solids from the nano-filtration unit were then charged in a separate tube and mixed with biocatalyst (cellulase loading: 10 filter paper units/g of substrate) at pH 5.5 and maintained at a temperature of about 50°C for 24 h to effect hydrolysis thereof. After completion of the hydrolysis, 10 mL of extra water (ambient temperature) was added to the hydrolysate stream to dissolve the released sugars. The produced sugars were then determined with standard method of DNS assay. Results obtained from the DNS assay are shown in the graph provided at FIG. 3.
[0058] De-polymerization of lignocellulosic biomass in a batch reactor
[0059] The pre-processed substrates (10 g dry weight) obtained above were transferred to Parr reactor (400 mL capacity) with Teflon liner. Then, 100 mL of catalyst solution (3 M MgCl2 + 1.5 % w/v of HNO3) was added to the material containing tubes. The solid to liquid ratio in the start of the hydrolysis reaction was maintained at 1: 10. To keep the contents in motion, the stirrer was kept on. The primary hydrolysis reaction was carried at 100 °C for 2 h, at mixing speed of 300 RPM. The secondary hydrolysis was carried with 0.5 % Wt. of BPO4 solid at 120°C for 1 h under mixing (500 RPM). The pH of the reaction mixture was acidic (~1.5). After completion of hydrolysis, 50 mL of extra water (ambient temperature) was added to dissolve the released sugars. The produced sugars were then determined with standard method of DNS assay. Results obtained from the DNS assay are shown in the graph provided at FIG. 4A and 4B.
[0060] The chemo-hydrolysis process when carried out with rice straw, wheat straw and sugarcane bagasse (as lignocellulosic biomass), an average hydrolysis of 35% – 45% could be observed. Interestingly, the process of the instant disclosure, when carried out with food grains like rice, wheat, millets etc. (as lignocellulosic biomass), the hydrolysis in the range of 20% to 45% could be achieved. Accordingly, the chemo-catalytic method of the instant disclosure for conversion of lignocellulosic biomass to glucose and other monomeric sugars is attractive from a bio-refinery point of view, as the two energy-intensive and time consuming unit operations of thermochemical pre-treatment and conventional enzymatic hydrolysis could be achieved in a single step. This would lead to considerable reduction in both capital expenditure and operating expenditure, thus making utilization of the lignocellulosic biomass more economically viable than the conventional methods. Further, the process of the present disclosure affords hydrolysis at relatively lower temperatures and at a high solid loading of about 10% w/v. The process of the present disclosure also affords near complete recovery of the catalyst from the hydrolysate, which can conveniently be recycled for solubilization/hydrolysis of fresh feedstock/biomass. Further, the catalyst-free sugar stream is completely fermentable using commonly available (conventional) microorganisms. Consequently, the advantageous process of the instant disclosure precludes the need of subjecting the lignocellulosic biomass to costly and energy intensive pre-treatment for deconstruction or dissolution of complex lignocellulose or carbohydrates, and affords production of fermentable sugars reducing the need of enzyme (biocatalyst) dosage by almost 75% as compared to the conventional processes and with minimal production of inhibitors. Lastly, the process of the instant disclosure affords utilization of multiple lignocellulosic feedstock/biomass such as rice straw, sugarcane bagasse, wheat straw, starchy food grains and other carbohydrate based biomass.

ADVANTAGES
[0061] The present disclosure relates to a process for de-polymerization of lignocellulosic biomass that is economical.
[0062] The present disclosure relates to a process for de-polymerization of lignocellulosic biomass that affords reduction in both capital expenditure and operating expenditure.
[0063] The present disclosure relates to a process for de-polymerization of lignocellulosic biomass that precludes the need of subjecting the lignocellulosic biomass to costly and energy intensive pre-treatment for deconstruction or dissolution of complex lignocellulose or carbohydrates.
[0064] The present disclosure relates to a process for de-polymerization of lignocellulosic biomass that affords production of fermentable sugars reducing the need of enzyme (biocatalyst) dosage by almost 75% as compared to the conventional processes and with minimal production of inhibitors.
[0065] The present disclosure relates to a process for de-polymerization of lignocellulosic biomass that affords utilization of multiple lignocellulosic feedstock/biomass such as rice straw, sugarcane bagasse, wheat straw, starchy food grains and other carbohydrate based biomass.