Method for producing surfactants

Abstract

Disclosed herein are methods of producing surfactants, in particular methods of producing alkyl polyglycosides from polysaccharide-containing materials using microwaves.

Description

[0001] Cross-reference

[0002] This application claims priority to Singapore Patent Application No. 10202303336W, filed on November 24, 2023, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present invention generally relates to methods for producing biobased surfactants from biomass. In particular, the present invention relates to methods for producing alkyl polyglycosides from polysaccharide-containing materials. Background Art

[0004] Surfactants, which are compounds that lower the surface tension between two substances, are widely used in various industries, including cleaning products, pharmaceuticals, and cosmetics. As a nonionic surfactant produced entirely from renewable resources, alkyl glycosides are eco-friendly and biodegradable, with excellent skin compatibility and surface activity, thus occupying a significant share of the current global surfactant market.

[0005] Currently, alkyl glycosides are produced on a large scale by direct Fischer glycosylation of monosaccharides with fatty alcohols. The raw material (anhydrous monosaccharides) is obtained by starch hydrolysis. The extended synthetic pathway and the strict requirements for raw material purity hinder economic competitiveness: the price of alkyl glycosides is approximately twice that of conventional fossil-based surfactant molecules, which limits their widespread use. Therefore, there is still a need for improved methods for producing alkyl glycosides that can achieve high yields and low production costs. Summary of the Invention

[0006] In one aspect, there is provided a method for producing alkyl polyglycosides from a polysaccharide-containing material, the method comprising: (i) contacting the polysaccharide-containing material with a catalyst and a fatty alcohol to form a mixture; (ii) using microwave heating to heat the mixture obtained in step (i) to produce alkyl polyglycosides. Brief Description of the Drawings

[0008] The present invention will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the drawings, wherein:

[0009] Figure 1 is a schematic representation of a general process flow diagram.

[0010] Figure 2 is a schematic representation of the LCA system boundaries for the production of butyl glycoside designed using microwave and conventional heating.

[0011] Figure 3 Shows the results of screening the reaction conditions for microwave-assisted transglycosylation. Figure 3a - 3d shows the effects of reaction temperature, reaction time, acid dosage, and water content on the yield of butyl glycoside, respectively. Reaction conditions: 3a: 500 mg of wheat bran, 7 mL of butanol, 50 mg of H 2 SO 4 (0.8 wt%), 3 h, using different reaction temperatures; 3b: at 90 °C, using different reaction times; 3c: using different wt% of H 2 SO 4 additive; and 3d: using different wt% of water additive. The experiments were conducted in triplicate for each condition, and the average yield of six products was reported, each with a corresponding standard deviation.

[0012] Figure 4 Shows the results of a comparative analysis of heating methods. 4a: Heating models of conventional and microwave systems; 4b: Real-time temperature and energy supply during microwave-assisted reactions; 4c: Total yields of alkyl glucosides in conventional and microwave systems during reactions; 4d: Kinetic study of the model alcoholysis reaction of cellobiose. The experiments for each condition were conducted in triplicate, and the average total product yield was reported, indicating the standard deviation. Each rate constant (k) is the average of three independent first-order kinetic curve measurements at a given temperature (T), where the standard deviation indicates variability; the activation energy (E a ) was derived from line fitting.

[0013] Figure 5 Shows the results of a comparison of engineering, environmental, and economic performances between microwave and conventional systems. 5a: Energy consumption; 5b: CO 2 emissions; 5c: Equipment cost; 5d: Operating costs of microwave and conventional systems. Each result represents the average of three independent simulations, each based on specific experimental data obtained under the same conditions, where the provided standard deviation indicates variability.

[0014] Figure 6 Shows the analysis results of the products obtained by microwave-assisted transglycosylation of wheat bran. 6a: Structural carbohydrate analysis of wheat bran before and after the reaction; 6b: Results of electrospray ionization mass spectrometry (ESI-MS) analysis to confirm the transglycosylation products; 6c: Results of high-performance liquid chromatography (HPLC) analysis; 6d: Results of heteronuclear single quantum coherence spectroscopy (HSQC) analysis. Reaction conditions: 500 mg of wheat bran, 7 mL of butanol, and 50 mg of H 2 SO 4 , heated by microwave at 90 °C for 3 h.

[0015] Figure 7Results of a comparison showing the influence of different heating methods on the bonding structure. 7a: Results of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis of the surface functional groups of wheat bran residue after reaction; 7b: Results of X-ray crystallography (XRD) analysis of the crystal structure of the sample; 7c: Photograph of the sample; 7d: Results of field emission scanning electron microscopy (FE-SEM) analysis of the morphology of the wheat bran sample; 7e: 13 Results of solid-state NMR analysis of C; 7f: Ratio of different types of carbon to C5 carbon in the sample.

[0016] The present invention is described in detail

[0017] The inventors of the present invention surprisingly found that the production of alkyl polyglycosides from polysaccharide-containing materials using microwaves can improve the yield of alkyl polyglycosides and / or reduce the production cost.

[0018] Accordingly, in one aspect, there is provided a method for producing alkyl polyglycosides from polysaccharide-containing materials, the method comprising: (i) contacting the polysaccharide-containing material with a catalyst and a fatty alcohol to form a mixture; (ii) heating the mixture obtained in step (i) using microwaves to produce alkyl polyglycosides.

[0019] In some instances, the method further comprises (iii) purifying the alkyl polyglycosides obtained in step (ii).

[0020] Alkyl polyglycosides are characterized by sugar units and hydrophobic alkyl chains. Alkyl polyglycosides differ in the length of the alkyl chain and the degree of polymerization of the sugar. Alkyl polyglycosides can be represented by the general formula G x –O–R, where G is the hydrophilic structural moiety derived from a reducing sugar, R is an alkyl group, and x is the degree of polymerization of the polyglycoside, i.e., the number of monosaccharide repeating units in the polyglycoside. The group –O–R is connected to G x via the anomeric carbon of the sugar residue to form an acetal functional group.

[0021] The alkyl polyglycoside can be linear or branched, saturated or unsaturated. Thus, in some instances, R is a linear alkyl group or a branched alkyl group, particularly a mono-branched alkyl group. In some instances, R is a saturated alkyl group. In some other instances, R is an unsaturated alkyl group. In some instances, R is a C2-C18, or C3-C17, or C4-C16, or C5-C15, or C6-C14, or C7-C13, or C8-C12, or C9-C11 alkyl group, or a C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, or C18 alkyl group. In some instances, R has an even number of carbon atoms. In some specific instances, R is a C4 alkyl group, i.e., the alkyl polyglycoside is a C4 alkyl polyglycoside. Examples of C4 alkyl polyglycosides include but are not limited to butyl polyglycosides of glucose, xylose, and arabinose.

[0022] Exemplary sugars from which G can be derived include but are not limited to glucose, xylose, arabinose, galactose, dextrose, sucrose, fructose, idose, gulose, maltose, isomaltose, maltotriose, lactose, cellobiose, mannose, ribose, lyxose, aldose, altrose, rhamnose, dextran, and talose. In some specific instances, G is derived from glucose, xylose, arabinose, galactose, and / or combinations thereof.

[0023] In some instances, the degree of polymerization x of a single alkyl polyglycoside molecule is 1, 2, 3, or 4. The average degree of polymerization x of a mixture of alkyl polyglycosides can be in the range of about 1.0 to about 4.0, or about 1.5 to about 3.5, or about 2.0 to about 3.0, or a number from about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4.0. In some specific instances, the average degree of polymerization x is in the range of about 1.0 to about 2.5.

[0024] Polysaccharides are long-chain polymeric carbohydrates that contain monosaccharide units bonded together by glycosidic linkages. Polysaccharides range in structure from linear to highly branched. Examples of polysaccharides include structural polysaccharides (such as hemicellulose, cellulose, and chitin) and storage polysaccharides (such as starch, glycogen, and galactan). In some instances, the polysaccharide in the polysaccharide-containing material used in the methods described herein is mainly hemicellulose or cellulose. In some specific instances, the polysaccharide in the polysaccharide-containing material used in the methods described herein is mainly hemicellulose.

[0025] Hemicellulose is a polysaccharide composed of pentoses, hexoses, deoxyhexoses, and / or combinations thereof linked by β-(1–4)-glycosidic bonds. Pentoses (also known as pentosans) are monosaccharides having five carbon atoms. Examples include, but are not limited to, xylose and arabinose. Hexoses (also known as hexosans) are monosaccharides having six carbon atoms. Examples include, but are not limited to, glucose, mannose, and galactose. Deoxysugars are sugars in which a hydroxyl group is replaced by a hydrogen atom. Examples of deoxyhexoses include, but are not limited to, rhamnose. Based on the monosaccharides present, hemicellulose can be designated as different types, including, but not limited to, xylan, arabinoxylan, xyloglucan, heteroxylan, glucomannan, and arabinogalactan. In some examples, hemicellulose contains xylose, arabinose, glucose, mannose, galactose, and / or rhamnose, each in an amount of about 5 to about 80, or about 10 to about 70, or about 20 to about 60, or about 30 to about 50 weight %, or about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 weight %, measured against the total weight of the hemicellulose. In some specific examples, hemicellulose contains about 25 to about 30 weight % glucose, about 20 to about 25 weight % xylose, and about 10% arabinose.

[0026] Cellulose is a linear polysaccharide formed by the linkage of glucose units through β-(1–4)-glycosidic bonds. The number of glucose units that make up cellulose can range from several hundred to several thousand.

[0027] Lignin is a polymer made by crosslinking monolignols. Examples of the three main monolignols are p -coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol.

[0028] In some instances, the polysaccharide-containing material is lignocellulosic biomass or contains lignocellulosic biomass. Lignocellulosic biomass comprises hemicellulose, cellulose, and lignin. Any biomass rich in hemicellulose, cellulose, and lignin is often referred to as lignocellulosic biomass. In some instances, hemicellulose is present in the lignocellulosic biomass in an amount of about 10 to about 90, or about 20 to about 80, or about 30 to about 70, or about 40 to about 60 weight percent, or in an amount of about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 weight percent, measured relative to the total weight of the lignocellulosic biomass. In some instances, cellulose is present in the lignocellulosic biomass in an amount of about 5 to about 50, or about 10 to about 40, or about 20 to about 30 weight percent, or in an amount of about 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 weight percent. In some instances, lignin is present in the lignocellulosic biomass in an amount of about 5 to about 70, or about 10 to about 60, or about 20 to about 50, or about 30 to about 40 weight percent, or in an amount of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 weight percent. In some instances, the lignocellulosic biomass contains about 30 weight percent hemicellulose, about 10 weight percent cellulose, and about 10 weight percent lignin. The lignocellulosic biomass may also include other components such as starch, protein, fat, and / or moisture. Examples of lignocellulosic biomass include, but are not limited to, wheat bran, wheat straw, barley husk, barley straw, rice straw, rice husk, oat straw, ray straw, corn cob, corn stover, bagasse, sorghum straw, empty fruit bunches of oil palm, mesocarp fiber of oil palm, oil palm leaves, oil palm trunks, coconut husks, and other agricultural side streams. In a specific instance, the lignocellulosic biomass is wheat bran. The lignocellulosic biomass as used in the methods described herein is typically present in its native state, which means that, compared to its state of existence in nature, they have not undergone any chemical transformation, particularly extraction using solvents and / or by enzymatic means.

[0029] In some instances, the polysaccharide-containing material used undergoes mechanical treatment, including but not limited to grinding, milling, crushing, rolling, and combinations thereof. The mechanical treatment is typically carried out to increase the surface area available for reaction of the polysaccharide-containing material, typically by reducing the size of the polysaccharide-containing material. In some instances, after the mechanical treatment, the size of the polysaccharide-containing material is less than or not greater than about 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 mm.

[0030] In some instances, before performing step (i) of the methods described herein, the polysaccharide-containing material used has not undergone enzymatic treatment and / or acid treatment. In some other instances, before performing step (i) of the methods described herein, the polysaccharide-containing material used has undergone enzymatic treatment and / or acid treatment, i.e., as a pretreatment of the polysaccharide-containing material. Such treatments are typically designed to improve the miscibility of the polysaccharide-containing material and do not result in the extraction of any bioactive compounds. In some specific instances, the enzymatic treatment or acid treatment is carried out in the presence of a reagent that improves miscibility. An example of such a reagent is an emulsifier. Examples of emulsifiers include, but are not limited to, phospholipids and polyvinyl alcohol; phase transfer catalysts such as polyethylene glycol; and quaternary ammonium salts such as benzyltriethylammonium chloride, methyltrioctylammonium chloride, and methyltributylammonium chloride. In some specific instances, the enzymatic treatment and / or acid treatment is carried out under reduced moisture conditions. In some instances, reduced moisture conditions mean that the weight % of water in the total enzymatic or acid treatment reaction system is about 0 to about 5.0, or about 0.2 to about 4.8, or about 0.4 to about 4.6, or about 0.6 to about 4.4, or about 0.8 to about 4.2, or about 1.0 to about 4.0, or about 1.2 to about 3.8, or about 1.4 to about 3.6, or about 1.6 to about 3.4, or about 1.8 to about 3.2, or about 2.0 to about 3.0, or about 2.2 to about 2.8, or about 2.4 to about 2.6 weight %, or about 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0 weight %.

[0031] In some instances, the catalyst used in the methods described herein is an acid catalyst. In some instances, the catalyst is a homogeneous acid catalyst. In some instances, the catalyst is a liquid acid catalyst. In some instances, the catalyst is a protonic acid, either an inorganic protonic acid or an organic protonic acid. A protonic acid is an acid that forms positive hydrogen ions (also known as oxonium ions) in aqueous solution. Examples of inorganic protonic acids include, but are not limited to, sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, hydrofluoric acid, chloric acid, carbonic acid, and sulfurous acid. Examples of organic protonic acids include, but are not limited to, acetic acid, citric acid, propionic acid, folic acid, lactic acid, formic acid, and malic acid. In some specific instances, the catalyst is sulfuric acid. In some other specific instances, the catalyst is acetic acid.

[0032] Fatty alcohols (also referred to as long-chain alcohols) are high molecular weight, straight-chain primary alcohols. In the methods described herein, the fatty alcohols used can act as solvents and / or transglycosylation agents. Fatty alcohols typically have an even number of carbon atoms and a single alcohol group (–OH) attached to the terminal carbon. In some instances, the fatty alcohols used are saturated. In some instances, the fatty alcohols used are unsaturated. In some instances, the fatty alcohols used are linear. In some other instances, the fatty alcohols used are branched. Fatty alcohols are often represented by the number of carbon atoms in the molecule. For example, “C12 alcohol” is an alcohol having 12 carbon atoms. In some instances, the fatty alcohols used are C2-C18 alcohols. In some instances, the fatty alcohols are C4-C22, C6-C20, C8-C18, C10-C16, or C12-C14 alcohols. In some specific instances, the fatty alcohol is C4 alcohol. In some instances, isomeric alcohols can be used. In some specific instances, the fatty alcohol is butanol. Isomeric alcohols of butanol include 1-butanol, 2-butanol, tert-butanol, and isobutanol. In one specific instance, the fatty alcohol is 1-butanol.

[0033] In some instances, in step (i) of the methods described herein, the catalyst and the fatty alcohol are added simultaneously to the polysaccharide-containing material. In some other instances, in step (i) of the methods described herein, the catalyst and the fatty alcohol are added sequentially to the polysaccharide-containing material. In some instances, the fatty alcohol is added first and then the catalyst is added to the polysaccharide-containing material. In some other instances, the catalyst is added first and then the fatty alcohol is added to the polysaccharide-containing material.

[0034] In some instances, steps (i) and (ii) are carried out simultaneously. In some other instances, steps (i) and (ii) are carried out sequentially. In some instances, when steps (i) and (ii) are carried out sequentially, step (ii) is carried out after step (i) is completed. The time taken to complete step (i) can depend on various factors such as the polysaccharide-containing material used, the amounts of catalyst and fatty alcohol, size and properties, and can be determined by those skilled in the art without undue experimentation. In some instances, the time taken to complete step (i) is about 5 to about 120, or about 10 to about 110, or about 20 to about 100, or about 30 to about 90, or about 40 to about 80, or about 50 to about 70 seconds, or about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 seconds. In some other instances, the time taken to complete step (i) is about 5 to about 120, or about 10 to about 110, or about 20 to about 100, or about 30 to about 90, or about 40 to about 80, or about 50 to about 70 minutes, or about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 minutes.

[0035] In some instances, the temperature in step (ii) is in the range of about 70 to about 180, or about 80 to about 170, or about 90 to about 160, or about 100 to about 150, or about 110 to about 140, or about 120 to about 130 °C, or at about 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or 180 °C. In some specific instances, the temperature is about 90 to about 150 °C. In some other specific instances, the temperature is about 90 to about 100 °C. The temperature used in the methods described herein is generally lower than the temperature used in conventional heating methods. In some instances, the temperature used in step (ii) is at least about 10, 20, 30, 40, 50, 60, 70, 80, 90, or 95% lower than the temperature used in the corresponding conventional heating method.

[0036] Using microwaves, the target temperature in step (ii) can be reached rapidly. In some examples, the time taken to reach the target temperature in step (ii) is within a few minutes or seconds. In some examples, the time taken is in the range of about 10 seconds to about 10 minutes, or about 20 seconds to about 9 minutes, or about 30 seconds to about 8 minutes, or about 40 seconds to about 7 minutes, or about 50 seconds to about 6 minutes, or about 1 to about 5 minutes, or about 2 to about 4 minutes, or about 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 seconds, or about 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 minutes. In some specific examples, the time taken is about 1 to about 2 minutes.

[0037] In some examples, step (ii) is carried out for about 10 minutes to about 24 hours, or about 20 minutes to about 22 hours, or about 30 minutes to about 20 hours, or about 1 to about 18 hours, or about 2 to about 16 hours, or about 3 to about 14 hours, or about 4 to about 12 hours, or about 5 to about 10 hours, or about 6 to about 8 hours, or about 5, 10, 15, 20, 30, 40, or 50 minutes, or about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 hours. In some specific examples, step (ii) is carried out for about 1 to about 9 hours. In some specific examples, step (ii) is carried out for about 3 to 5 hours.

[0038] Stirring is generally used to carry out step (i) and / or step (ii) of the methods described herein. This means that the reactor in which the method is carried out is equipped with a stirring mechanism. Examples of suitable stirring mechanisms include stirrers equipped with "anchor" type or "impeller" type blades. In some examples, the stirring mechanism is set at a speed of about 20 to about 200, or about 30 to about 190, or about 40 to about 180, or about 50 to about 170, or about 60 to about 160, or about 70 to about 150, or about 80 to about 140, or about 90 to about 130, or about 100 to about 120 rpm, or at about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, or 200 rpm.

[0039] In some instances, the weight % of the polysaccharide-containing material in the total reaction system is about 1 to about 20, or about 2 to about 19, or about 3 to about 18, or about 4 to about 17, or about 5 to about 16, or about 6 to about 15, or about 7 to about 14, or about 8 to about 13, or about 9 to about 12, or about 10 to about 11 weight %, or about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 weight %. In some specific instances, the weight % of the polysaccharide-containing material is about 8 to about 10 weight %.

[0040] In some instances, the weight % of the catalyst in the total reaction system is about 0.1 to about 5.0, or about 0.2 to about 4.8, or 0.3 to about 4.6, or about 0.4 to about 4.4, or about 0.5 to about 4.2, or about 0.6 to about 4.0, or about 0.7 to about 3.8, or about 0.8 to about 3.6, or about 0.9 to about 3.4, or about 1.0 to about 3.2, or about 1.2 to about 3.0, or about 1.4 to about 2.8, or about 1.6 to about 2.6, or about 1.8 to about 2.4, or about 2.0 to about 2.2 weight %, or about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0 weight %. In some specific instances, the weight % of the catalyst is about 0.8 to about 1.0 weight %, or about 0.9 weight %.

[0041] In some instances, the weight % of the fatty alcohol in the total reaction system is about 5 to about 95, or about 10 to about 90, or about 15 to about 85, or about 20 to about 80, or about 25 to about 75, or about 30 to about 70, or about 35 to about 65, or about 40 to about 60, or about 45 to about 55 weight %, or about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95 weight %. In some specific instances, the weight % of the fatty alcohol is about 90 to about 95 weight %.

[0042] In some instances, the reaction system is free of water. In some other instances, water will make up the remainder of the reaction system. Thus, in some instances, the weight % of water in the total reaction system is from about 0 to about 10.0, or about 0.5 to about 9.5, or about 1.0 to about 9.0, or about 1.5 to about 8.5, or about 2.0 to about 8.0, or about 2.5 to about 7.5, or about 3.0 to about 7.0, or about 3.5 to about 6.5, or about 4.0 to about 6.0, or about 4.5 to about 5.5 weight %, or about 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2, 7.4, 7.6, 7.8, 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8, or 10.0 weight %. In some specific instances, the weight % of water is from about 0 to about 2.5%, or about 0 weight %.

[0043] In some instances, the methods described herein are carried out in the absence of any solvents (other than the fatty alcohols used). In particular, steps (i) and / or (ii) of the method are carried out in the absence of any organic solvents (other than the fatty alcohols used) and preferably also in the absence of water (other than that provided by the reactants, particularly the catalyst).

[0044] In some instances, the weight ratio of the polysaccharide-containing material to the catalyst is from about 20:1 to 2:1, or about 18:1 to about 4:1, or about 16:1 to about 6:1, or about 14:1 to about 8:1, or about 12:1 to about 10:1, or about 20:1, 19:1, 18:1, 17:1, 16:1, 15:1, 14:1, 13:1, 12:1, 11:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, or 2:1. In some specific instances, the weight ratio of the polysaccharide-containing material to the catalyst is about 10:1.

[0045] The fatty alcohol is usually in excess, i.e., unreacted fatty alcohol will remain after the reaction is completed and / or after the polysaccharide-containing material has reacted completely or substantially. In some examples, the weight ratio of the fatty alcohol to the polysaccharide-containing material is about 20:1 to 2:1, or about 18:1 to about 4:1, or about 16:1 to about 6:1, or about 14:1 to about 8:1, or about 12:1 to about 10:1, or about 20:1, 19:1, 18:1, 17:1, 16:1, 15:1, 14:1, 13:1, 12:1, 11:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, or 2:1. In some specific examples, the weight ratio of the fatty alcohol to the polysaccharide-containing material is about 12:1 to about 10:1, or about 11:1.

[0046] In some examples, the weight ratio of the catalyst to the fatty alcohol is about 1:150 to about 1:10, or about 1:140 to about 1:20, or about 1:130 to about 1:30, or about 1:120 to about 1:40, or about 1:110 to about 1:50, or about 1:100 to about 1:60, or about 1:90 to about 1:70, or about 1:150, 1:145, 1:140, 1:135, 1:130, 1:125, 1:120, 1:115, 1:110, 1:105, 1:100, 1:95, 1:90, 1:85, 1:80, 1:75, 1:70, 1:65, 1:60, 1:55, 1:50, 1:45, 1:40, 1:35, 1:30, 1:25, 1:20, 1:15, or 1:10. In some specific examples, the weight ratio of the catalyst to the fatty alcohol is about 1:110.

[0047] In some specific examples, the weight ratio of the polysaccharide-containing material: fatty alcohol: catalyst is about 10:110:1.

[0048] In some specific examples of the method as described herein, the polysaccharide-containing material is wheat bran, the catalyst is sulfuric acid, the alcohol is 1-butanol, the temperature in step (ii) is about 90 to about 100 °C, step (ii) is carried out for about 5 hours, the weight % of wheat bran in the total reaction system is about 8 to about 10 weight %, the weight % of sulfuric acid in the total reaction system is about 0.8 to about 1.0 weight %, the weight % of 1-butanol in the total reaction system is about 0.9 to about 90 weight %, and the weight % of water in the total reaction system is about 0%.

[0049] In some examples, the method as described herein is an enzyme-free method, i.e., no enzyme is used in the method, or specifically, no enzyme is used in step (i) or (ii). In some other examples, the method as described herein is a microorganism-free method, i.e., no microorganism is used in the method, or specifically, no microorganism is used in step (i) or (ii).

[0050] After completion or cessation of step (ii), purification step (iii) is carried out. A cooling process is typically carried out to reduce the temperature to a level suitable for carrying out purification step (iii). In some instances, the temperature is reduced to about 10 to about 70, or about 15 to about 65, or about 20 to about 60, or about 25 to about 55, or about 30 to about 50, or about 35 to about 45 °C, or about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 °C.

[0051] Purification step (iii) is typically carried out to remove any excess and / or unreacted reagents, and / or to concentrate the produced alkyl polyglycoside. Such excess or unreacted reagents typically include unreacted polysaccharide-containing materials, fatty alcohols, and / or catalysts. Any suitable method or combination thereof can be used to carry out purification step (iii). Examples of suitable purification methods include, but are not limited to, filtration, neutralization, distillation, evaporation, crystallization, centrifugation, and / or chromatography. Filtration and / or centrifugation are typically used to separate and / or remove any solid residues. Neutralization is typically carried out to deactivate the catalyst. The reagent used in neutralization varies depending on the length of the hydrocarbon alkyl chain. Examples of neutralization reagents include, but are not limited to, sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH 4 OH), magnesium hydroxide (Mg(OH) 2 ), calcium hydroxide (Ca(OH) 2 ), sodium carbonate (Na 2 CO 3 ), calcium carbonate (CaCO 3 ), and organic bases such as triethanolamine. In some instances, the reagent used in neutralization is a solid reagent. Distillation, evaporation, and / or filtration are typically carried out to remove excess fatty alcohol. If any solvent other than fatty alcohol is used, such solvent can also be removed in purification step (iii). Any unreacted reagent can be separated, purified, and / or recycled for future production cycles.

[0052] The methods described herein are typically carried out at atmospheric pressure, although reduced pressure and / or increased pressure can also be used for at least part of the method, particularly steps (i), (ii), and / or (iii) of the method. In some specific examples, step (i) is carried out at atmospheric pressure, reduced pressure, or increased pressure. In some specific examples, step (ii) is carried out at atmospheric pressure, reduced pressure, or increased pressure. In some specific examples, step (iii) is carried out at atmospheric pressure, reduced pressure, or increased pressure. In some more specific examples, step (iii) is carried out at reduced pressure. As used herein, the term "reduced" pressure means a pressure that is about 5 to about 50, or about 10 to about 45, about 15 to about 40, about 20 to about 35, about 25 to about 30%, or at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50% lower than atmospheric pressure. As used herein, the term "increased" pressure means a pressure that is about 5 to about 50, or about 10 to about 45, about 15 to about 40, about 20 to about 35, about 25 to about 30%, or at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50% higher than atmospheric pressure.

[0053] Depending on the polysaccharide-containing material and / or fatty alcohol used, the methods described herein can be used to produce various alkyl polyglycosides. Examples of alkyl polyglycosides produced using the methods described herein include, but are not limited to, alkyl glucosides, alkyl xylosides, alkyl arabinosides, and mixtures thereof. When the fatty alcohol used is butanol, specific examples include, but are not limited to, butyl glucoside, butyl xyloside, butyl arabinoside, and mixtures thereof.

[0054] Compared to alkyl polyglycosides made using the corresponding conventional methods, alkyl polyglycosides made by the methods described herein exhibit improved yields. In some examples, the yield of alkyl polyglycoside is at least about 10, 20, 30, 40, 50, 60, 70, 80, or 90 wt%. In some examples, compared to alkyl polyglycosides made using the corresponding conventional methods with all reaction conditions the same, the methods described herein result in at least 10, 20, 30, 40, 50, 60, 70, 80, or 90% greater improved yields of alkyl polyglycoside.

[0055] Compared to using the corresponding conventional methods, the methods described herein also result in reduced reaction time or production time required to obtain a specific amount of alkyl polyglycoside. In some examples, compared to alkyl polyglycosides made using the corresponding conventional methods with all reaction conditions the same, the methods described herein result in at least 10, 20, 30, 40, 50, 60, 70, 80, or 90% reduction in production time.

[0056] The alkyl polyglycosides made by the methods described herein can be in liquid form or in solid form, such as in the form of flakes or beads, depending on the nature of the alkyl hydrocarbon chain R. When the alkyl polyglycosides made by the methods described herein are in liquid form, further processing (such as evaporation, concentration, crystallization, and / or filtration) can be carried out to concentrate the obtained product.

[0057] The alkyl polyglycosides made by the methods described herein can be used in a variety of products and in a variety of forms of products. The products include consumer products such as detergents, soaps, shampoos, and emulsions. The products can be in forms such as liquid, semi-liquid, suspension, emulsion, gel, or solid.

[0058] The invention illustratively described herein can be suitably practiced in the absence of any one or more elements, one or more limitations that are not specifically disclosed herein. Thus, for example, terms such as "comprising", "including", "containing", etc. should be understood broadly rather than restrictively. Additionally, the terms and expressions used herein have been used as descriptive terms and not of limitation, and are not intended to exclude any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed invention. Accordingly, it is understood that although the invention has been specifically disclosed by preferred embodiments and optional features, modifications and variations of the invention embodied herein can be made by those skilled in the art, and such modifications and variations are considered to be within the scope of the invention.

[0059] As used in this application, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. For example, the term "genetic marker" includes multiple genetic markers, including mixtures and their combinations.

[0060] As used herein, the term "about" typically means ±5% of the stated value, more typically ±4% of the stated value, more typically ±3% of the stated value, more typically ±2% of the stated value, even more typically ±1% of the stated value, and even more typically ±0.5% of the stated value.

[0061] Throughout this disclosure, some examples may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the disclosed range. Accordingly, the description of a range should be considered to specifically disclose all possible sub-ranges as well as the individual values within that range. For example, the description of a range such as 1 - 6 should be considered to specifically disclose sub-ranges such as 1 - 3, 1 - 4, 1 - 5, 2 - 4, 2 - 6, 3 - 6, etc., as well as the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0062] As used herein, "w / w", "by weight", "weight %", "percent by weight", "wt%", and other grammatical variants are used synonymously to denote the ratio of the mass of a component in a composition to the mass of the entire composition (unless otherwise specified). For example, when the amount of a particular component is stated as 1 weight % (w / w) of a composition, the mass of that component is 1% of the mass of the entire composition. Similarly, when the amount of a component is 50% (w / w) of the composition, the mass of that component is 50% of the entire mass of the composition. When only a concentration, amount, or percentage (without units) is listed, it is understood that the concentration or percentage is a concentration or percentage by weight.

[0063] Some examples may also be described herein broadly and generally. Each of the narrower species and subgeneric groupings falling within the overall disclosure also forms part of the disclosure. This includes the general description of the examples, where conditional or negative limitations remove any subject matter from the genus, whether or not the deleted material is specifically recited herein.

[0064] The present invention is described herein broadly and generally. Each of the narrower species and subgeneric groupings falling within the overall disclosure also forms part of the invention. This includes the general description of the invention, where conditional or negative limitations remove any subject matter from the genus, whether or not the deleted material is specifically recited herein.

[0065] Other examples are in the following claims and non-limiting examples. Additionally, when describing the features or aspects of the present invention in terms of a Markush group, those skilled in the art will recognize that the invention is also thereby described in terms of any single member or subgroup of members of the Markush group. Examples

[0066] Materials and Methods

[0067] Chemicals and Materials

[0068] Wheat bran biomass was obtained as an agricultural by-product stream from Wilmar International Limited. The wheat bran was ground prior to use to achieve a uniform particle size distribution (<1 mm). It includes 1-butanol (>99.8%), sulfuric acid (H 2 SO 4 )(96.0–98.0%), sodium hydroxide (NaOH) (>98.0%), D-(+)-cellobiose (>99.0%), D-(+)-glucose (>99.5%), L-(+)-arabinose (>99.5%), D-(+)-xylose (>99.0%), dimethyl sulfoxide (DMSO) (>99.9%), and deuterium sulfate (D 2 SO 4)(96.0–98.0%) of the chemicals were purchased from Sigma-Aldrich. Deuterated methanol (CD 3 OD) (>99.9%) and deuterium oxide (D 2 O) (>99.9%) were sourced from Cambridge Isotope Laboratories. All chemicals were of analytical grade and used without further purification.

[0069] Biomass Characterization

[0070] The complete compositional analysis of wheat bran was carried out using the gravimetric method (Anderson and Ydesdale, 1980) specifically for cereal-based products. The received wheat bran was found to include cellulose (8.3 ± 0.2 wt%), hemicellulose (30.4 ± 2.3 wt%), starch (21.5 ± 0.8 wt%), Klason lignin (10.9 ± 0.4 wt%), protein (12.6 ± 0.7 wt%), fat (3.5 ± 1.0 wt%), and moisture (12.8 ± 1.7 wt%). Additionally, the carbohydrate distribution of wheat bran was analyzed by the National Renewable Energy Laboratory method (Sluiter et al., 2008), revealing glucose (26.7 ± 1.5 wt%), xylose (20.0 ± 0.9 wt%), and arabinose (9.6 ± 0.4 wt%). All analyses were performed in triplicate.

[0071] General Procedures

[0072] A typical transglycosylation reaction involved adding 500 mg of wheat bran, 7 mL of 1-butanol, and 50 mg of H 2 SO 4 to a 100 mL Teflon reaction vessel. The sealed vessel was then placed in an Anton Paar Multiwave Pro reactor equipped with a P / T-sensor. During the reaction, the mixture was rapidly heated to the set temperature within approximately 60 to 120 s and maintained at this constant temperature for 1 to 9 h. Once the reaction was complete, the reactor automatically cooled the mixture to 55 °C using the built-in convection fan.

[0073] For the conventional heating process, the reaction mixture was stirred in a pressurized tube immersed in an oil bath. Both the reaction vessel and the oil bath were heated from room temperature and gradually reached the set temperature, taking about 20 - 30 min. The temperature was then maintained at the set point for a fixed duration.

[0074] After cooling, the product mixture was centrifuged to separate the wheat bran residue from the liquid fraction. The residue was rinsed three times with 10 mL of acetone. The combined aliquots were neutralized with 6 M NaOH to a pH of approximately 7. Excess acetone and butanol were removed under reduced pressure via rotary evaporation. The concentrated product was extracted with water to a final volume of 25 mL and subsequently analyzed using high-performance liquid chromatography (HPLC) to quantify the product: butyl glycoside. Quantification was based on carbon mass balance:

[0075]

[0076] m p is the measured carbon mass of the product (α / β-Glu-OBu, α / β-Xyl-OBu, or α / β-Ara-OBu) obtained from HPLC measurements. f(carbon) eff is the effective carbon mass fraction of the product, calculated as: (carbon mass per molecule of product – carbon mass per molecule of butanol) / carbon mass per molecule of product. m s refers to the carbon mass of glucose, xylose, or arabinose in the wheat bran material.

[0077] Analytical Methods

[0078] Quantification of the alkyl glycoside product was carried out using an HPLC Shimadzu DGU-20A5R system equipped with a Hi-Plex H column (7.7 × 300 mm × 8 μm) operating at a temperature of 60 °C. A refractive index detector was employed and maintained at the same temperature for detection. The mobile phase consisted of 5 mM H 2 SO 4 aqueous solution at a flow rate of 0.6 mL / min. Typically, the aqueous reaction mixture was filtered through a 0.45 μm PES syringe filter. Subsequently, a 10 μL volume of this filtered sample was injected into the HPLC system for analysis. Quantification relied on the external standard method, using standard alkyl glycoside compounds synthesized by Fischer glycosylation of glucose, xylose, and arabinose and purified by column chromatography to construct a calibration curve. The limits of detection (LOD) and quantification (LOQ) were calculated according to the guidelines of the International Conference on Harmonization (ICH), which employed the slope and standard deviation of the calibration curve. These parameters were obtained using the OriginPro2021 program. The concentration of the test solution was greater than the LOD and LOQ.

[0079] Performed on samples dissolved in D 2 O using a Bruker Ascend400 NMR spectrometer operating at 400 MHz 11H liquid nuclear magnetic resonance (NMR) and 1 1H– 13 13C liquid heteronuclear single quantum coherence spectroscopy (HSQC). Solid-state 13 13C NMR spectroscopy of wheat bran residue was performed using a Bruker AVNEO400 solid NMR spectrometer operating at a spinning rate of 10 kHz. Qualitative analysis of the products was carried out based on their molecular weights using electrospray ionization mass spectrometry (ESI-MS) on a Bruker MicroTOF-Q system, where the filtered reaction aqueous solution was directly injected into the spectrometer chamber at 10 μL / min. The surface functional groups of the reacted wheat bran residue were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) in absorption mode at a resolution of 4 cm -1 −1 in the spectral range of 400–4000 cm -1 −1 with 64 scans using a Thermo Scientific Nicolet iS50 FT-IR spectrometer. X-ray crystallography (XRD) measurements from 10° to 90° were performed using a Bruker D8 Advance X-ray diffractometer operating at room temperature with Cu Kα radiation ( 40 kV, 20 mA) to determine the crystal structure of the solid samples. The surface morphology of the wheat bran residue samples was analyzed using a JEOL JSM-7610F field emission scanning electron microscope (FE-SEM) at an accelerating voltage of 15 kV after coating with platinum using a JEOL JFC-1300 sputter coater before observation.

[0080] Hydrogen-Deuterium Exchange Experiments

[0081] To compare the extent of hydrogen bond network disruption by different heating methods, hydrogen–deuterium (H–D) exchange experiments were carried out according to a method reported in the literature (with minor modifications). Briefly, transglycosylation of wheat bran was carried out using a method similar to the general procedure, where CD 3 OD was used instead of butanol and D 2 2SO 4 4 was used instead of H 2 2SO 4 4. The resulting mixture was vacuum filtered, and the recovered wheat bran residue was washed with CD 3 OD to remove the excess acid. After drying, the solid was analyzed using ATR-FTIR. A sugar ring O–D peak was observed near a wavenumber of 2500 cm -1 −1, which was significantly different from the O–H peak (3400 cm -1 −1) of the non-deuterated sugar. Since the breakage of hydrogen bonds is a prerequisite for H–D exchange, the detection of the O–D peak in the IR spectrum indicates significant disruption of the hydrogen bond network.

[0082] Process Modeling

[0083] Process modeling for microwave heating and conventional heating processes was performed using the ASPEN PLUS V12 program. Figure 1 ) Briefly, wheat bran obtained as an agricultural by-product stream was ground into a powder and combined with 1-butanol before entering the transglycosylation reactor. Sulfuric acid was added to the mixture. Then, the heating unit HX-1 was activated to heat the mixture to the reaction temperature and maintain it at that temperature. After leaving the transglycosylation reactor (R-1), the product stream was filtered by a filter press to separate the unreacted wheat bran residue from the process stream. Since the residual wheat bran still contains a significant carbohydrate content, it can be reused as a raw material for alternative applications (such as biofuel production or animal feed) instead of being disposed of as waste. The liquid fraction enters the neutralization reactor (R-2), where caustic soda is added to neutralize the acid catalyst, forming insoluble sulfates. Subsequently, the product mixture undergoes a secondary filtration process to remove the salts, which act as by-products and desiccants, binding and extracting the water generated during the process. The filtrate is then introduced into an evaporator (EVA) to separate the butanol in the gas phase and the product in the liquid phase. The butanol vapor is condensed into a liquid by a condenser (HX-2) and recycled for future production cycles. The main difference between the designs lies in the transglycosylation reactor type and the heating unit: the microwave design utilizes a microwave reactor driven by a microwave radiator (HX-1), while the conventional process employs a stirred tank reactor surrounded by a heat exchanger (HX-1). Under both microwave and conventional heating conditions, batch reaction data obtained from experiments with a duration of 5 h at 90 °C were used for modeling purposes. The microwave heating configuration was determined to be a semi-continuous process, processing 100 kg / h of wheat bran and producing approximately 24 kg / h of butyl glycoside. To ensure a proper comparison, the feed flow rate of the conventional heating was adjusted to produce an equivalent product output.

[0084] Techno-Economic Analysis (TEA)

[0085] Based on the process model, a preliminary TEA was conducted to evaluate the economic performance of the two designs. The analysis focused on cost estimations by analyzing two key parameters (naked module cost and operating cost). The CAPCOST program (Turton, 2013) was used to estimate the naked module costs of all process units except grinders and mixers. Due to limited process information in the model, the standard method described in the Turton approach could not be used to estimate grinder costs. Therefore, grinder costs were excluded to maintain the consistency and rigor of the cost estimation results. The mixer served as a virtual module for simulation purposes only. In actual implementation, the wheat bran and butanol streams could be directly introduced into the stirred reactor tank. Thus, the mixer was excluded from this study. The construction material for all process units except evaporators and condensers was assumed to be 316 stainless steel. This material was the most cost-effective option capable of withstanding the required degree of corrosion in the process. The materials for evaporators and condensers were assumed to be carbon steel as these units were used to recover non-corrosive butanol from the process. The latest Chemical Engineering Plant Cost Index (CEPCI) value of 750 was used for the estimation. The CAPCOST program was also used to estimate the operating (process facilities and raw materials) costs. The unit costs of heating and cooling media were obtained using Turton's method (Turton, 2013), while the unit costs of all materials were cited from relevant online databases. The cost of wheat bran was not included in the study as the background involved integrating the process into an existing wheat flour production facility. Thus, wheat bran could be obtained directly as an agricultural by-product.

[0086] Life Cycle Assessment

[0087] As Figure 2 shown, an ex-ante LCA was conducted. The system boundaries included the production of raw materials required for the process and the process itself. Two main indicators were selected to evaluate the environmental impacts of the microwave and conventional processes: (1) primary energy consumption, which included the energy required for raw material production and the heat exchanger load in the process, and (2) CO 2 emissions caused by the same factors. To calculate the equivalent primary energy consumption in operation and material production, conversion factors of 1.17 MJ of primary energy / MJ of heat and 12.7 MJ of primary energy / kWh of electricity from the GaBi database were applied. The CO 2 emissions and energy consumption of raw materials were estimated based on data from the Federal LCA Commons database or relevant literature. For the CO 2 emissions generated during operation, the GHG (greenhouse gas) emission conversion factor facilitated the conversion of process energy into CO 2 emissions.

[0088] Statistical Analysis

[0089] All experiments were conducted independently in triplicate. The results of three independent experiments were used for TEA and LCA studies. Numbers report the mean values, where error bars represent the standard deviation. One-way ANOVA (P < 0.05) was used to analyze the statistical differences between the results.

[0090] Results and Discussion

[0091] Green Surfactant Production via Microwave-Assisted Transglycosylation of Wheat Bran

[0092] Wheat bran is a carbohydrate-rich biomass, and its components mainly include hemicellulose, cellulose, lignin, and protein. According to the structural carbohydrate analysis, the main monosaccharide units of wheat bran consist of glucose (∼27 wt%), xylose (∼20 wt%), and arabinose (∼10 wt%). In the initial test, the transglycosylation of wheat bran was carried out under microwave heating, using butanol as the solvent and transglycosylation agent, and 0.8 wt% (wt% of the total system) H 2 SO 4 as the acid catalyst. The analysis of the solid residue after 3 h of reaction showed a significant reduction in monosaccharide units (especially pentoses) ( Figure 6 a), indicating the efficient conversion of polysaccharides in wheat bran. To confirm the transglycosylation products, ESI-MS analysis was performed. Two representative signals at m / z 229.13 and 259.14 were detected in the ESI-MS spectrum ( Figure 6 b), which were attributed to the butyl glycosides of pentoses [(C 9 H 18 O 5 )+Na] + and the butyl glycosides of hexoses [(C 10 H 20 O 6 )+Na] + . The butyl glycosides were further separated by HPLC. By comparing with the standard samples, the glycosides of pentoses were identified as butyl xyloside (Xyl-OBu) and butyl arabinoside (Ara-OBu), while the glycosides of hexoses were identified as butyl glucoside (Glu-OBu) ( Figure 6 c).

[0093] In the 1In the 1H NMR spectrum, representative doublets were confirmed at 4.82 / 4.36 ppm, 4.79 / 4.31 ppm, and 4.84 / 4.25 ppm, respectively, attributed to the acetal protons in the diastereoisomers of Glu-OBu, Xyl-OBu, and Ara-OBu. Considering that the acetal protons of Glu-OBu, Xyl-OBu, and Ara-OBu would overlap in the one-dimensional spectrum of the mixed product, HSQC was performed, and the diastereoisomers of Glu-OBu, Xyl-OBu, and Ara-OBu with pyranose ring structures were clearly distinguished and confirmed in HSQC( Figure 6 d), and the butyl glycoside of arabinose with a furanose ring structure was also detected as a by-product. Since the alkyl chain is hydrophobic and the sugar head group is hydrophilic, Xyl-OBu, Ara-OBu, and Glu-OBu have been identified as green surfactants.

[0094] Through the transglycosylation process, wheat bran biomass directly produces Glu-OBu, Xyl-OBu, and Ara-OBu surfactants in a microwave heating environment at 90 °C. Historically, the transglycosylation of carbohydrate biomass typically occurs at reaction temperatures greater than 130 °C to ensure a suitable product yield. However, with the help of microwave technology, the transglycosylation of wheat bran biomass can occur at a lower temperature of 90 °C.

[0095] Effects of Time, Temperature, Acid Concentration, and Water Content

[0096] The effects of reaction time, temperature, acid concentration, and water content were further explored. As Figure 3 shown in a, after a 3-h reaction, the total yield of alkyl glycosides was 6% at 70 °C. Increasing to 90 °C led to a significant improvement in transglycosylation (26%), as evidenced by the higher yields of Xyl-OBu and Ara-OBu rather than Glu-OBu. This observation indicates that the transglycosylation process mainly occurs in hemicellulose, suggesting that the hemicellulose part in wheat bran is more prone to transglycosylation than other carbohydrate components. Further increasing the reaction temperature to 150 °C further improved the yield to 35%. Reaction temperatures greater than 150 °C led to the humification and carbonization of wheat bran. At 90 °C, a monotonically decreasing trend was observed starting from 5 h( Figure 3 b).

[0097] As Figure 3 shown in c, in the absence of H 2 SO 4In the case of almost no reaction occurs, but when the concentration increases to a high value of 5 wt%, a decrease in the total yield is also observed. Further analysis of the product distribution reveals that the yield of Glu-OBu product increases with the increase in acid concentration. On the contrary, the yields of Xyl-OBu and Ara-OBu products increase, reach a plateau at an acid dosage of 0.8 wt%, and then decrease as the acid concentration reaches 5 wt%. This indicates that the surfactant molecules derived from pentoses are less stable than those derived from hexoses and are therefore more prone to humification in highly concentrated and dehydrated acid environments. Further screening of Amber lys t, ZSM, Al 2 O 3 and Dowex as solid acid catalysts, however, gave poor results (see Table 1), which indicates that microwave-assisted transglycosylation is mainly catalyzed by free H + rather than Bronsted acid sites at / near the solid surface. Several Lewis acid catalysts were investigated, including Cu 2 SO 4 、Fe 2 SO 4 、SnCl 2 、ZnSO 4 and CrCl 3 (see Table 1). However, none of them showed significant activity towards the desired transformation. This lack of reactivity can be attributed to their lower acidity compared to proton acids.

[0098] Table 1. Yields (wt%) obtained by using different solid acid catalysts (wt%) and different Lewis acid catalysts (mmol).

[0099]

[0100]

[0101] To prevent humification during the conversion of carbohydrate biomass, a catalytic amount of water can be added to inhibit dehydration. However, in this system, up to a concentration of 2.4 wt%, the addition of water had no significant effect on the reaction; beyond this threshold, an inhibitory effect was observed, as Figure 3 shown in d. The possible reason is that water can hydrolyze the glycosidic bonds in surfactant molecules and dilute the acid strength, thus adversely affecting the product yield. It is reasonable that when the water content is below 2.4 wt%, the promoting effect due to reduced humification offsets the hindering effect. Once the water content exceeds 2.4 wt%, the dilution effect outweighs the benefits, resulting in a significant decrease in yield.

[0102] Mechanistic Studies

[0103] Microwave Heating vs. Conventional Heating

[0104] The microwave system heats the reaction via an inside-out approach, where microwave radiation directly transfers energy to the molecules of the reaction mixture, causing dipole rotation and ionic conduction, while the conventional system heats via conduction through the reactor wall and convective heat transfer ( Figure 4 a). Except for the intense fluctuations within the first 60 - 120 s, the reaction temperature and energy supply in the microwave system are generally stable ( Figure 4 b). Nevertheless, the reaction rate and product yield are significantly enhanced by microwave heating ( Figure 4 c). In particular, under microwave heating conditions, an optimized yield of 26% is achieved in 5 h at 90 °C, while under conventional heating, the reaction takes more than 10 h to reach an optimized yield of 17% (60% in the microwave system). The reduced time and improved yield observed under microwave radiation suggest possible non-thermal activation induced by microwaves during the biomass conversion process.

[0105] Effect of Microwave on Hydrogen Bonds

[0106] Proton - deuterium (H - D) exchange experiments were conducted to investigate the activation of hydrogen bonds in wheat bran by microwaves. In the presence (solid line) or absence (dashed line) of 0.8 wt% D 2 SO 4 and, the raw wheat bran was treated with deuterated methanol (CD 3 OD) at 90 °C by conventional heating or microwave heating ( Figure 7 a). The resulting samples were monitored by ATR - FTIR to estimate the degree of H - D exchange by taking advantage of the significant difference between the OH peak (at approximately 3400 cm -1 ) and the OD peak (at approximately 2500 cm -1 ). In the absence of D 2 SO 4 , some H - D exchange occurred after conventional heating treatment, while a lower degree of H - D exchange occurred after microwave treatment. Conversely, with the addition of D 2 SO 4 , the degree of H - D exchange in the microwave system increased significantly, while the improvement in the degree of H - D exchange in the conventional system was less, indicating that partially protonated hydroxyl groups are more likely to be activated by microwaves, leading to the activation of the hydrogen bond network within wheat bran.

[0107] XRD spectra showed that the wheat bran samples remained almost unchanged after conventional heating treatment, while the samples treated by microwave heating showed two weak peaks at approximately 26° and 44° ( Figure 7 b), possibly attributed to graphitic carbon. This further indicates that the microwave environment not only activates hydrogen bonds but also enhances the dehydration of hydroxyl groups. The primary dehydration of hydroxyl groups is one of the possible pathways to initiate the transglycosylation reaction. Despite the similar macroscopic morphology of the treated wheat bran (Figure 7 c), but FE-SEM clearly shows that microwave heating significantly disrupts the connections between the components of wheat bran compared to conventional heating ( Figure 7 d).

[0108] Effect of Microwave on Glycosidic Bonds

[0109] The effect of microwaves on the activation of chemical bonds, particularly glycosidic bonds in wheat bran, was further investigated. For this purpose, solid-state 13 C NMR analysis of the treated samples was carried out ( Figure 7 e). Peaks at approximately 100.2, 78.9, 70.4, and 59.7 ppm were attributed to C1, C4, C2,3,5, and C6 of the pyranose ring, respectively. The C1 peak was further deconvoluted into two bands for cellulose and hemicellulose, while the C4 peak was also deconvoluted into bands for crystalline cellulose and amorphous cellulose / hemicellulose. The C1 and C4 peaks are mainly affected by the widely present β-(1,4) glycosidic bonds in carbohydrate biomass. The distribution of these carbon bands was normalized and compared based on C2,3,5. It was shown that C4 (amorphous cellulose / hemicellulose) and C6 were significantly consumed ( Figure 7 f). A possible explanation is that the microwave activation mechanism follows an H + transfer pathway from the protonated C6 hydroxyl group to the O atom of the glycosidic bond (C1-O-C4).

[0110] To further demonstrate the microwave activation effect on glycosidic bonds, a kinetic study was carried out using cellobiose as a model compound. Compared to the case of the conventional heating system, the reaction rate in the microwave system increased significantly with increasing reaction temperature, and the apparent activation energy in the microwave system was 106 kJ / mol, much lower than that of the conventional heating system (148 kJ / mol) ( Figure 4 d). The decrease in the activation energy of the microwave system is a strong indicator of the lower energy barrier of the reaction under microwave radiation, indicating that microwave radiation catalyzes the reaction by stabilizing the transition state or by providing a different reaction pathway. The mechanistic influence of the microwave-assisted reaction indicates a specific, non-thermal effect on the chemical structure of the carbohydrate moiety in wheat bran particularly through the resonance frequency vibration of the OH group on the C6 carbon. Under microwave radiation, this OH group vibrates at its resonance frequency, resulting in proton dissociation. This selective vibration and subsequent protonation promote the disruption of the hydrogen bond network, as evidenced by a higher degree of H-D exchange. In addition, the same mechanism promotes the transfer of protons from the activated, protonated C6 hydroxyl group to the oxygen atom of the glycosidic bond, effectively promoting its cleavage. 13The difference in carbon ratios observed in solid-state NMR spectra further confirmed this. Additionally, kinetic studies revealing lower activation energies under microwave conditions supported this theory, indicating that microwave radiation catalyzes reactions by providing an alternative, non-thermal pathway for bond breaking that is not available under conventional thermal conditions. These results together suggest that due to the activation of both intermolecular hydrogen bonds and recalcitrant glycosidic bonds, the transglycosylation reaction is particularly favorable in a microwave environment, leading to the efficient conversion of wheat bran biomass to alkyl glycosides at lower temperatures.

[0111] Life Cycle Assessment and Cost Estimation

[0112] LCA analysis showed that when compared to the conventional heating process, the microwave process demonstrated higher energy efficiency, resulting in a 42% reduction in energy consumption ( Figure 5 a). The primary energy consumption in both the microwave and conventional designs was mainly attributed to plant operation, accounting for 77% and 82% respectively. Although the impact of material energy consumption was relatively small, the microwave process could significantly reduce the energy use associated with acid catalysts and basic neutralizing agents by approximately two-thirds. This improvement was attributed to increased conversion efficiency and reduced catalyst requirements per unit mass of product. Additionally, due to a significant reduction in heating and cooling requirements during the separation process in the product stream, the overall operating energy consumption experienced a 45% reduction. Overall, integrating the microwave reactor into the process led to a significant reduction in primary energy consumption.

[0113] The carbon footprint of the process is shown as Figure 5 b. When manufacturing unit mass of butyl glycoside, the microwave process led to a 56% reduction in CO 2 emissions compared to the conventional process. As expected, plant operation accounted for the majority of emissions, mainly due to the large heating and cooling loads required when operating the evaporator and condenser for butanol recovery. The reduced consumption of acid catalysts and basic reagents significantly contributed to reducing the carbon footprint associated with these chemicals. This finding indicates that replacing conventional heating methods with microwave heating in the transglycosylation process can achieve a more environmentally friendly production process.

[0114] To better understand the engineering advantages of microwave heating in butyl glycoside production, process models for both microwave heating and conventional heating designs were developed using wheat bran as the raw material. As Figure 5As shown in c), due to the large process load required to separate a large amount of unreacted butanol from the process stream, the evaporator cost accounts for the largest share among all process units. Notably, the combined cost of the transglycosylation reactor and the evaporator in the microwave heating design is 45% lower than that in the conventional heating design, mainly due to the significantly lower stream flow rates required to achieve the same product yield in the microwave process as in the conventional process. In addition, due to the reduced consumption of the acid catalyst and the associated neutralization load using sodium hydroxide, the raw material cost is significantly lower in the microwave design. Despite the overall lower utility cost of the microwave design, the utility cost of the transglycosylation reactor is approximately five times higher than that of the conventional process ( Figure 5 d), and this difference can be traced back to the difference in the form of energy used to drive the transglycosylation reactor. The heating load in the microwave reactor is provided by electricity, whose unit cost is nine times higher than that of the heating medium (low-pressure steam) used in the conventional-designed tank reactor, thus resulting in a significantly higher energy cost for the transglycosylation reactor in the microwave design. The manufacturing cost of the alkyl polyglycoside produced by the microwave method is estimated to be 7 USD / kg, which is 30% lower than the cost produced by conventional heating (Table 2). Compared with biosurfactants synthesized by microorganisms (such as sophorolipid and rhamnolipid), microwave synthesis is significantly more cost-effective, by a factor of 3 to 100 times.

[0115] Table 2. Manufacturing costs of microwave and conventional heating designs.

[0116]

[0117]

[0118] Overall, microwave heating shows economic and environmental advantages for the alcoholysis process applied to lignocellulosic biomass. In particular, it results in a 42% reduction in energy consumption, a 56% reduction in CO 2 emissions, a 44% reduction in equipment cost, and a 35% reduction in operating cost, resulting in a production cost of 7 USD / kg for butyl glycoside.

[0119] Conclusions

[0120] In summary, microwave-assisted transglycosylation significantly improves the conversion efficiency of wheat bran to alkyl polyglycosides, achieving a total surfactant yield of 29% at 90 °C. Compared with the conventional heating method, this represents a 53% increase in yield and a 72% reduction in reaction time. LCA and TEA show significant reductions in the following aspects: energy consumption (42%), CO 2Emissions (56%) and equipment, operation, and production costs (over 30%). These findings suggest that microwave treatment could provide a more efficient, cost-effective, and environmentally friendly method for surfactant production from agricultural waste, with potential implications for a wider range of biomass conversion applications.

[0121] References

[0122] Anderson, N.E., Ydesdale, F.M.C., 1980. An analysis of the dietary fiber content of a standard wheat bran. J. Food Sci. 45(2), 336–340.

[0123] Sluiter, A., Hames, B., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., Crocker, D., 2008. Determination of structural carbohydrates and lignin in biomass. Laboratory Analytical Procedure (LAP). National Renewable Energy Laboratory.

[0124] Turton, R., 2013. Analysis, Synthesis, and Design of Chemical Processes, 4th international ed. Pearson, Upper Saddle River, NJ.

Claims

1. A method for producing alkyl polysaccharide from a polysaccharide-containing material, the method comprising the following steps: (i) contacting the polysaccharide-containing material with a catalyst and a fatty alcohol to form a mixture; (ii) heating the mixture obtained in step (i) using microwaves to produce the alkyl polyglycoside.

2. The method according to claim 1, further comprising: (iii) purifying the alkyl polysaccharide obtained in step (ii).

3. The method according to claim 1 or 2, wherein the method is an enzyme-free method and / or a microorganism-free method.

4. The method according to claim 1 or 2, wherein the polysaccharide is hemicellulose.

5. The method according to claim 4, wherein the hemicellulose is formed from monosaccharides selected from the group consisting of xylose, arabinose, glucose, mannose, galactose, rhamnose and mixtures thereof. The method according to claim 5 , wherein the hemicellulose is formed from glucose, xylose and / or arabinose.

7. The method of claim 1 or 2, wherein the polysaccharide-containing material is lignocellulosic biomass.

8. The method of claim 7, wherein the lignocellulosic biomass is selected from the group consisting of wheat bran, wheat straw, barley husk, barley straw, rice straw, rice husk, oat straw, stalks, corn cobs, corn stover, sugarcane bagasse, sorghum straw, oil palm empty fruit bunches, oil palm mesocarp fibers, oil palm leaves, oil palm trunks, coconut shells and other agricultural by-streams.

9. The method of claim 7, wherein the lignocellulosic biomass is wheat bran.

10. The method according to claim 1 or 2, wherein the fatty alcohol is a C4 alcohol, preferably butanol.

11. The method according to claim 1 or 2, wherein the catalyst is an acid, preferably a protic acid, more preferably an inorganic protic acid selected from sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, hydrofluoric acid, chloric acid, carbonic acid and sulfurous acid, and more preferably sulfuric acid.

12. The method according to claim 1 or 2, wherein the alkyl polysaccharide produced is a C4 alkyl polysaccharide, preferably a butyl polysaccharide of glucose, xylose and / or arabinose.

13. The method according to claim 1 or 2, wherein the weight % of the polysaccharide-containing material in the total reaction system is 1 to 20 weight %, preferably 8 to 10 weight %.

14. The method according to claim 1 or 2, wherein the weight % of the catalyst in the total reaction system is 0.5 to 2.0 weight %, preferably 0.8 to 1.0 weight %.

15. The method according to claim 1 or 2, wherein the weight % of the fatty alcohol in the total reaction system is 70 to 95 weight %, preferably 90 to 95 weight %.

16. The method according to claim 1 or 2, wherein the weight % of water in the total reaction system is 0 to 2.0 weight %, preferably about 0 weight %.

17. The process according to claim 1 or 2, wherein the temperature in step (ii) is in the range of 90 to 150°C, preferably 90 to 100°C.

18. The method according to claim 1 or 2, wherein step (ii) is performed for 1 to 9 hours, preferably 3 to 5 hours.

19. The method according to claim 1 or 2, wherein the polysaccharide-containing material is wheat bran, the catalyst is sulfuric acid, the alcohol is butanol, the temperature in step (ii) is 90 to 100°C, step (ii) is performed for about 5 hours, the weight % of wheat bran in the total reaction system is 8 to 10 weight %, the weight % of sulfuric acid in the total reaction system is 0.8 to 1.0%, the weight % of butanol in the total reaction system is 90 to 95 weight %, and the weight % of water in the total reaction system is about 0%.

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