Method for producing glucose or xylooligosaccharide by treating tobacco stems with preheated water

Abstract

The invention discloses a method for producing glucose or xylooligosaccharide by treating tobacco stems with preheated water. The method for producing the xylooligosaccharide by treating the tobacco stems with the preheated water comprises the following steps: (1) grinding the tobacco stems into powder; (2) dispersing the tobacco stem powder into water, and heating to a certain temperature; and (3) filtering and separating to obtain a liquid which is a solution containing xylooligosaccharide. The method for producing glucose by treating tobacco stems with preheated water comprises the following steps: (1) grinding the tobacco stems into powder; (2) dispersing the tobacco stem powder into water, and heating to a certain temperature; (3) filtering and separating to obtain solid residues; (4) preparing a cellulase suspension; (5) adding the solid residues into a cellulase suspension for enzymolysis at a certain temperature; and (6) separating to obtain clear liquid, namely a glucose solution. However, according to the tobacco stem material, the total yield of xylooligosaccharide is the highest at about 90 DEG C; the total yield of glucose is the highest at about 110 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of tobacco stem biomass treatment, specifically relating to a method for producing glucose or xylooligosaccharides from tobacco stems through preheating treatment. Background Art

[0002] Rapid global population and energy demand are depleting fossil resources and triggering climate change, prompting humanity to explore renewable resources for green and sustainable production. Lignocellulosic biomass is the most abundant and diverse renewable resource on Earth. However, due to the high rigidity of its plant cell walls, it hinders the conversion into high-value-added products. Therefore, accelerating biomass pretreatment and conversion technologies is essential for producing various biological products.

[0003] Tobacco is one of the world's most important non-food economic crops, widely cultivated in Asia, Africa, South America, and North America, and the consumption of tobacco leaves for cigarette production has long been a major economic driver. However, tobacco stems are one of the most common byproducts and wastes in tobacco processing and are not yet well utilized. Discarding these tobacco stem wastes results in the loss of significant amounts of polysaccharides and carbon resources; efficient extraction and utilization through various pretreatments are crucial for converting tobacco stems into valuable products. Therefore, tobacco stem pretreatment has attracted widespread attention and warrants in-depth research.

[0004] Currently, the pretreatment methods for tobacco stems are similar to those for lignocellulose, mainly including physical, chemical, biological, and combined methods. However, the treatment strategy largely depends on the varying degrees of resistance among diverse biomass resources. Steam explosion is one of the common treatment methods for tobacco biomass. While steam explosion technology for tobacco stems maintains the inherent stiffness of the tobacco stem (TS) fibers during treatment, it requires sophisticated equipment. In addition, there is chemical acid treatment, which has advantages such as high pyrolysis efficiency compared to alkaline methods, but chemical treatments are generally polluting. Other methods include freeze-drying and ball milling, but these are too costly. Therefore, there is an urgent need to find a green and pollution-free method for pretreating tobacco stems to achieve high yields of glucose and xylooligosaccharides.

[0005] Hydrothermal pretreatment (HTP) has proven to be an effective method for processing tobacco stems (TS), showing great promise for the separation and further utilization of cell wall components, particularly polysaccharides. However, the changes in the microstructure and physicochemical structure of tobacco stems, especially lignin and cellulose, are not fully elucidated. Furthermore, there is limited research on the bioconversion of extracted polysaccharides into fermentable sugars. Therefore, it is necessary to optimize existing methods to achieve high-value conversion of tobacco stem resources. Summary of the Invention

[0006] This invention provides a method for producing glucose or xylooligosaccharides by preheating tobacco stems.

[0007] The technical solution of this invention is as follows:

[0008] This invention discloses a method for producing xylooligosaccharides from tobacco stems through preheating treatment, comprising the following steps:

[0009] (1) Air dry the tobacco stems, generally with a moisture content of no more than 10%; then grind them into powder of 20-80 mesh;

[0010] (2) Heat the tobacco stem powder in an aqueous dispersion with a solid-liquid ratio of 1g:(8-12)ml at a heating rate of 1.0-2.0℃ / min to 60℃-120℃ and hold for 0.5-2h; then cool to 0℃-10℃ and hold for 10min-30min.

[0011] (3) Filter and separate, and wash the solid residue at least three times; the resulting liquid is a solution containing xylooligosaccharides; remove water to obtain xylooligosaccharides.

[0012] Preferably, the solid-liquid ratio is 1g:10ml, the heating rate is 1.5℃ / min, the temperature is raised to 90℃ and held for 1h; then the temperature is cooled to 4℃ and held for 20min.

[0013] This invention also discloses a method for producing glucose from tobacco stems through preheating treatment, comprising the following steps:

[0014] (1) Air dry the tobacco stems, generally with a moisture content of no more than 10%; grind them into powder of 20-80 mesh;

[0015] (2) Heat the tobacco stem powder in an aqueous dispersion with a solid-liquid ratio of 1g:(8-12)ml at a heating rate of 1.0-2.0℃ / min to 80℃-150℃ and hold for 0.5-2h; then cool to 0℃-10℃ and hold for 10min-30min.

[0016] (3) Filter and wash the solid residue at least three times to obtain solid residue;

[0017] (4) Prepare cellulase suspension;

[0018] (5) Add the solid residue obtained in step (3) to the cellulase suspension in step (4) and enzymatically hydrolyze it at 45-55℃ for 60-90h.

[0019] (6) The clear liquid obtained after separation is glucose solution.

[0020] Preferably, the solid-liquid ratio is 1g:10ml, the heating rate is 1.5℃ / min, the temperature is raised to 110℃ and held for 1h; then the temperature is cooled to 4℃ and held for 20min.

[0021] Preferably, the cellulase suspension is prepared by mixing a citrate-sodium citrate buffer solution, tetracycline, cellulase, and water to obtain the cellulase suspension; wherein the citrate-sodium citrate buffer solution is 0.1M with a pH of 4.8; the amount of cellulase added is 10 FPU / ml substrate; and the amount of tetracycline added is 3 μL / ml.

[0022] Preferably, the ratio of solid residue to cellulase suspension is 1g:20ml.

[0023] Preferably, enzymatic hydrolysis is performed at 50°C for 72 hours.

[0024] The beneficial effects of this invention are:

[0025] Existing hydrothermal treatment techniques for other cellulose components, yielding glucose or xylooligosaccharides, require relatively high temperatures to achieve high yields: for example, 200℃ for poplar wood (see Enhanced enzymatic digestibility of poplar wood by quickhydrothermal Treatment, Bioresource Technology, 2020, 302, 122795.), and above 150℃ for corn stalks (see patents CN118562912 and CN116479069A). In contrast, the material used in this invention is tobacco stalks, which achieves the highest total yield of xylooligosaccharides (51.83%) at around 90℃ and the highest total glucose yield (77.40%) at around 110℃. Detailed Implementation

[0026] To make the present invention easier to understand, specific embodiments of the invention will be described in detail below, but this is only for illustration and not for limiting the present invention.

[0027] Example 1: Preparation of xylooligosaccharides from tobacco stems by preheating with hot water.

[0028] (1) Air dry TS (provided by Yunnan China Tobacco Industry Co., Ltd.) and grind it into powder that passes through a 20-80 mesh sieve using a grinder;

[0029] (2) TS powder was placed in a stainless steel reactor containing water for HTP process; the reaction temperatures were 50℃, 70℃, 90℃, 110℃, 130℃, 150℃ and 170℃, the solid-liquid ratio was 1g:10ml, the heating rate was 1.5℃ / min and the reaction time was 1h; then the preheated sample was placed in a cold water bath to cool for 20min, and the solid residue and liquid were separated by filtration; the solid residue was washed three times with deionized water, and the obtained liquid was stored at 4℃ and diluted to 5g / L, and recorded as TL-50℃, TL-70℃, TL-90℃, TL-110℃, TL-130℃, TL-150℃ and TL-170℃ respectively;

[0030] (3) The molecular weight (MW) and mass distribution of oligosaccharides / monosaccharides at TL-50℃, TL-70℃, TL-90℃, TL-110℃, TL-130℃, TL-150℃, and TL-170℃ were determined using gel permeation chromatography (GPC) in an HPLC system. The results are shown in Table 1 below (X6 indicates a degree of polymerization of 6, and the same applies to others); among them,

[0031] Xylooligosaccharide (XOS) (DP=2-6) content (%) = (amount of autohydrolyzed xylooligosaccharides with degree of polymerization 2-6 (g)) ÷ (amount of xylan in untreated TS-0 sample (g)) * 100%.

[0032] Table 1. Xylooligosaccharide yield and total yield

[0033] X1 X2 X3 X4 X5 X6 Total yield of xylooligosaccharides TL-50℃ 3.86％ 2.29％ 0.11％ 0％ 0％ 0％ 6.26％ TL-70℃ 5.03％ 2.74％ 4.88％ 0.16％ 0.57％ 0％ 13.38％ TL-90℃ 11.34％ 23.48％ 24.94％ 2.63％ 0.78％ 0.00％ 51.83％ TL-110℃ 12.83％ 24.94％ 1.68％ 3.46％ 0.00％ 4.14％ 34.23％ TL-130℃ 13.13％ 24.17％ 1.55％ 2.27％ 0.00％ 0.53％ 28.53％ TL-150℃ 14.63％ 19.71％ 0.12％ 1.42％ 0.00％ 0.00％ 21.26％ TL-170℃ 14.28％ 16.85％ 0.27％ 1.06％ 0.00％ 0.00％ 19.18％

[0034] As shown in Table 1, when the material is tobacco stem and the hydrothermal treatment temperature is around 90℃, the total yield of xylooligosaccharides is the highest, reaching 51.83%.

[0035] Example 2: Preheating tobacco stems to prepare glucose.

[0036] (1) Air dry TS (provided by Yunnan China Tobacco Industry Co., Ltd.) and grind it into powder that passes through a 20-80 mesh sieve using a grinder;

[0037] (2) TS powder was placed in a stainless steel reactor containing water for HTP process; the reaction temperatures were 70℃, 90℃, 110℃, 130℃, 150℃ and 170℃, the solid-liquid ratio was 1g:10ml, the heating rate was 1.5℃ / min and the reaction time was 1h; then the pretreated sample was placed in a cold water bath to cool for 20min, and the solid residue and liquid were separated by filtration; the solid residue was washed three times with deionized water and the solid residues were named TS-70, TS-90, TS-110, TS-130, TS-150 and TS-170.

[0038] (3) Preparation of cellulase suspension: The cellulase suspension is obtained by mixing citrate-sodium citrate buffer solution, tetracycline, dextran cellulase, and water; wherein, the citrate-sodium citrate buffer solution is 0.1M with a pH of 4.8; the amount of cellulase added is 10 FPU / ml substrate; and the amount of tetracycline added is 3 μL / ml.

[0039] (4) Add solid residue and cellulase suspension at a ratio of 1g:20ml and enzymatically hydrolyze at 50℃ for 72h.

[0040] (5) Separate to obtain a clear liquid;

[0041] (6) The molecular weight (MW) and mass distribution of oligosaccharides / monosaccharides of TS-70, TS-90, TS-110, TS-130, TS-150 and TS-170 were determined by gel permeation chromatography (GPC) in an HPLC system. The results are shown in Table 2 below; among them,

[0042] Glucose content (%) = Glucose content in hydrolysate (g) / Mass of original enzymatic hydrolysate (g) * 100%.

[0043] Table 2 Glucose yield

[0044] raw material TS-70 TS-90 TS-110 TS-130 TS-150 TS-170 Glucose yield / % 64.62 70.02 71.63 77.40 63.93 57.09 55.83

[0045] As shown in Table 2, when the material is tobacco stem and the hydrothermal treatment temperature is around 110℃, the total glucose yield is the highest, reaching 77.40%.

[0046] Comparative Example 1: Enhanced enzymatic digestibility of poplar wood by quickhydrothermal Treatment, Bioresource Technology, 2020, 302, 122795. The literature describes hot water treatment of poplar wood, with temperatures reaching up to 200°C, achieving a glucose yield of 70%. This is lower than the temperature and effect described in the embodiments of this invention.

[0047] Comparative Example 2: Patent CN118562912, "Method for High-Efficiency Co-production of Xylooligosaccharides and Glucose through Ball Milling and Composite Pretreatment," uses hydrothermal treatment of corn stalks at temperatures exceeding 185℃, and combines this with ball milling, resulting in high energy consumption and a maximum Xylooligosaccharide (X2-X4) yield of only 28.1%. This is lower than the temperature and effect described in the embodiments of this invention.

[0048] Comparative Example 3: Patent CN116479069A uses pressurized hydrothermal pretreatment of corn stalks at temperatures exceeding 150°C, and its xylooligosaccharide yield is 47.7%, which is lower than the temperature and effect in the embodiments of this invention.

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing xylooligosaccharides from tobacco stems through preheating treatment, characterized in that, Includes the following steps, (1) Dry the tobacco stems and grind them into powder of 20-80 mesh; (2) Heat the tobacco stem powder in an aqueous dispersion with a solid-liquid ratio of 1g:(8-12)ml at a heating rate of 1.0-2.0℃ / min to 60℃-120℃ and hold for 0.5-2h; then cool to 0℃-10℃ and hold for 10min-30min. (3) Filter and separate, and wash the solid residue at least three times; the resulting liquid is a solution containing xylooligosaccharides.

2. The method according to claim 1, characterized in that, The solid-liquid ratio was 1g:10ml, and the temperature was increased to 90℃ at a rate of 1.5℃ / min and held for 1 hour; then cooled to 4℃ and held for 20 minutes.

3. A method for producing glucose from tobacco stems through preheated water treatment, characterized in that, Includes the following steps, (1) Dry the tobacco stems and grind them into powder of 20-80 mesh; (2) Heat the tobacco stem powder in an aqueous dispersion with a solid-liquid ratio of 1g:(8-12)ml at a heating rate of 1.0-2.0℃ / min to 80℃-150℃ and hold for 0.5-2h; then cool to 0℃-10℃ and hold for 10min-30min. (3) Filter and wash the solid residue at least three times to obtain solid residue; (4) Prepare cellulase suspension; (5) Add the solid residue obtained in step (3) to the cellulase suspension in step (4) and enzymatically hydrolyze it at 45-55℃ for 60-90h. (6) The clear liquid obtained after separation is glucose solution.

4. The method according to claim 3, characterized in that, The solid-liquid ratio was 1g:10ml, and the temperature was increased to 110℃ at a rate of 1.5℃ / min and held for 1h; then cooled to 4℃ and held for 20min.

5. The method according to claim 3, characterized in that, The cellulase suspension was prepared by mixing citrate-sodium citrate buffer solution, tetracycline, cellulase, and water. The citrate-sodium citrate buffer solution was 0.1 M with a pH of 4.

8. The amount of cellulase added was 10 FPU / ml substrate, and the amount of tetracycline added was 3 μL / ml.

6. The method according to claim 3, characterized in that, The ratio of solid residue to cellulase suspension is 1g:20ml.

7. The method according to claim 3, characterized in that, Enzymatic hydrolysis at 50℃ for 72 hours.