Method for producing bacterial cellulose by pretreating papermaking sludge through acid heating method

Abstract

The invention discloses a method for producing bacterial cellulose by pretreating papermaking sludge through an acid-heat method, and belongs to the technical field of papermaking sludge resource utilization. In order to solve the problem that the paper mill sludge is difficult to safely dispose, the method comprises the following steps: adding a surfactant into the paper mill sludge, stirring, filtering and drying, obtaining paper mill sludge hydrolysate through an acid heating method, removing acid radicals and other inhibitors in the hydrolysate, adjusting the pH value to 6.0-6.8, diluting the hydrolysate, adding a nitrogen source into the diluted hydrolysate, and carrying out heat preservation for 2-3 hours, thereby obtaining the paper mill sludge. And producing bacterial cellulose as an acetobacter xylinum culture solution. The bacterial cellulose prepared by the method is equivalent to the bacterial cellulose prepared by a glucose culture medium with equivalent sugar content in yield and performance, so that the paper mill sludge can be used as a potential carbon source for bacterial cellulose production. The treatment method is environment-friendly and remarkable in economic benefit, and meanwhile has the advantages of being easy to operate, good in yield and performance and wide in prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization of papermaking sludge, and particularly relates to a method for sustainably producing bacterial cellulose by using papermaking sludge as a fermentation medium of Acetobacter xylinum. Background Art

[0002] With the gradual growth of production and consumption of China's papermaking industry, the disposal of papermaking sludge has become an important issue. Traditional treatment methods such as incineration, landfill and composting often have many disadvantages. Papermaking sludge contains rich biomass. Converting the biomass in papermaking sludge into high-value products not only reduces environmental pollution, but also generates economic and social value. Bacterial cellulose is a biodegradable three-dimensional porous structure nanobiomaterial with high crystallinity and high polymerization degree synthesized by certain microorganisms. Compared with plant cellulose, it does not contain lignin and hemicellulose, so it has the characteristics of high purity; at the same time, it also has unique high mechanical properties and high biocompatibility, which makes it have broad application prospects in many fields such as medical materials, food industry and environmental treatment. However, the high culture medium cost of bacterial cellulose limits its production and application. Using papermaking sludge as a potential culture medium source for bacterial cellulose production is a solution. Therefore, an innovative treatment method is urgently needed to solve the problems existing in the existing technology. Summary of the invention

[0003] In order to solve the problem that papermaking sludge generated in the process of paper production in paper mills is difficult to safely dispose of, the present invention provides a method for bioconverting papermaking sludge into bacterial cellulose, that is, a method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge. The method can effectively bioconvert papermaking sludge into bacterial cellulose after saccharification to achieve biomass recovery and safe disposal of papermaking sludge.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge, comprising the following steps:

[0006] Step 1, adding a nonionic surfactant to the wet papermaking sludge, stirring evenly and drying to obtain dry papermaking sludge;

[0007] Step 2: hydrolyzing the dry papermaking sludge by an acid-heat method to obtain a papermaking sludge hydrolyzate;

[0008] Step 3: remove acid radicals and other inhibitors in the hydrolyzate, adjust the pH to 6.0-6.8, dilute the hydrolyzate, add a nitrogen source to the diluted hydrolyzate, sterilize it and use it as a fermentation medium for Acetobacter xylinum, and inoculate Acetobacter xylinum to produce bacterial cellulose.

[0009] In step 1, the non-ionic surfactant is fatty alcohol polyoxyethylene ether, and the addition amount is 0.1% to 0.5% of the dry papermaking sludge.

[0010] In step 1, the wet papermaking sludge to which the nonionic surfactant is added is stirred evenly and then ultrasonicated for 30 to 60 minutes, the filter residue is filtered out, and then dried at 65° C. to constant weight.

[0011] In step 2, after the dry papermaking sludge is ground into powder, sulfuric acid solution is added, the concentration of the sulfuric acid solution is 20%-35%, the addition amount is 10-20 ml / g, the temperature of the hydrolysis reaction is 90-110°C, and the reaction time is 90-120 min. Preferably, the concentration of the sulfuric acid solution is 20%, the addition amount is 15 ml / g, the reaction temperature is 100°C, and the reaction time is 100 min.

[0012] In step three, an excess of 1M barium hydroxide is added to the hydrolyzate to filter and remove sulfate, 3% to 6% w / v of activated carbon is added to the filtered filtrate to remove other inhibitors (furfural and lignin), and then filtered to obtain a detoxified hydrolyzate, and 1M sodium hydroxide is used to adjust the pH of the detoxified hydrolyzate to 6.0 to 6.8.

[0013] In step three, the hydrolyzate is diluted 1-3 times; 1% peptone and 1% yeast extract are used as nitrogen sources based on the volume of the diluted hydrolyzate, and the sterilization temperature is 121° C. for 20 min.

[0014] In step 3, the xylinum Acetobacter seed solution is inoculated at an inoculation amount of 6 to 10% of the volume of the xylinum Acetobacter fermentation medium, and then the bacterial cellulose crude product is statically cultured at 25 to 30° C. in a constant temperature incubator for 7 to 14 days. The bacterial cellulose crude product is taken out from the fermentation medium, placed in a 0.1 to 0.2 M sodium hydroxide solution and heated in a 90° C. water bath for 2 to 4 hours, the pH is adjusted to neutral with acetic acid, and the bacterial cellulose membrane is washed with deionized water several times to obtain purified bacterial cellulose.

[0015] In step three, the preparation method of the xylinum Acetobacter seed liquid is as follows: inoculate the xylinum Acetobacter stored in a 4°C refrigerator into a fresh plate culture medium, culture it in a 30°C constant temperature incubator for 48 hours until a single colony grows on the plate, and then use an inoculation loop to pick up the single colony on the plate culture medium to 50 ml of seed culture medium under sterile conditions, and culture it at 30°C and 200rpm for 24 hours to obtain the xylinum Acetobacter seed liquid for fermentation.

[0016] Among them, the configuration of the seed culture medium: glucose 20g / L, peptone 5g / L, yeast extract 5g / L, and the pH was adjusted to 6.5; the configuration of the plate culture medium: glucose 20g / L, peptone 5g / L, yeast extract 5g / L, agar 20g / L, and the pH was adjusted to 6.5.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention is a resource utilization method for the biological conversion of papermaking sludge produced by a paper mill into bacterial cellulose. For example, after 5g of dry weight of papermaking sludge is pretreated by an acid-heat method, the diluted hydrolyzate can be used as a culture medium to produce 10g / L of bacterial cellulose, and its tensile strength is about 0.04Mpa. The present invention can effectively utilize papermaking sludge to produce high-value products bacterial cellulose, reduce environmental pollution, and generate economic value. The bacterial cellulose produced in a glucose culture medium containing a considerable amount of reducing sugar has a yield of 12g / L and a tensile strength of 0.03Mpa, which is equivalent to the yield and performance of the present invention. The present invention proposes for the first time that papermaking sludge can be used as a potential carbon source for bacterial cellulose production. The method is simple to operate, not only reduces the production cost of bacterial cellulose, but also solves the environmental problem caused by the difficulty in safely disposing of papermaking sludge, is environmentally friendly and has significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : Schematic diagram of the hydrolyzate of papermaking sludge after acid pyrolysis and removal of sulfate and other inhibitors, without adding nitrogen source.

[0020] Figure 2 : Schematic diagram of the culture process after inoculating Acetobacter xylinum with 100 ml of hydrolyzate as the culture medium.

[0021] Figure 3 : Schematic diagram of bacterial cellulose after acquisition and purification. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Embodiment 1:

[0024] A method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge, comprising the following steps:

[0025] 1. Take 1L of fresh paper sludge, add a non-ionic surfactant (fatty alcohol polyoxyethylene ether) at 0.5% of the dry weight of the sludge, stir and ultrasonically vibrate for 30 minutes. Take the filter residue after filtration, and then dry it at 65°C to constant weight. Weigh the dry paper sludge and crush it into fine powder. Add a 30% mass fraction of sulfuric acid solution at an addition amount of 10 ml / g, react at 105°C for 90 minutes to obtain a hydrolyzate, and then use 1M barium hydroxide to remove sulfate. After filtering, add 5% w / v activated carbon to remove other inhibitors (furfural and lignin), filter to obtain a detoxified hydrolyzate, use 1M sodium hydroxide to adjust the pH to 6.5, and use it for the next step of preparing the culture medium. The schematic diagram of the hydrolyzate after acid pyrolysis of paper sludge to remove sulfate and other inhibitors (furfural and lignin) is as follows Figure 1 shown.

[0026] 2. Dilute the paper sludge hydrolyzate by 2 times, add 1% peptone and 1% yeast paste to the volume of the diluted hydrolyzate, sterilize in an autoclave at 121°C for 20 minutes, and then cool to obtain a fermentation medium. Inoculate the xylella fastidiosa stored in a 4°C refrigerator into a fresh plate culture medium, culture it in a constant temperature incubator at 30°C for 48 hours until a single colony grows on the plate, and aseptically use an inoculation loop to pick up a single colony on the plate culture medium into 50 ml of seed culture medium, and culture it at 30°C and 200rpm for 24 hours to obtain seed liquid. Inoculate the seed liquid into the 2-fold diluted fermentation medium at a 10% inoculation rate, and culture it at 30°C for 7 days. The schematic diagram of the culture process is shown below. Figure 2 As shown, after the culture is completed, the bacterial cellulose is taken out from the fermentation medium and placed in a 0.2M sodium hydroxide solution and heated in a water bath at 90°C for 2 hours. Then, it is adjusted to neutral with acetic acid and washed with deionized water several times to obtain purified bacterial cellulose, as shown in FIG. Figure 3 shown.

[0027] Among them, the configuration of the seed culture medium: glucose 20g / L, peptone 5g / L, yeast extract 5g / L, and the pH was adjusted to 6.5; the configuration of the plate culture medium: glucose 20g / L, peptone 5g / L, yeast extract 5g / L, agar 20g / L, and the pH was adjusted to 6.5.

[0028] According to the above method, the bacterial cellulose yield of 5g dry weight paper sludge is 11g / L, and the tensile strength is about 0.04Mpa. Under the same culture conditions, the yield of xylem Gluconacetobacter in glucose reference medium is 12g / L, and the tensile strength is 0.03Mpa. The yield and performance of the two are comparable. Among them, the configuration of glucose reference medium: glucose 20g / L, peptone 5g / L, yeast extract 5g / L, sodium dihydrogen phosphate 2.7g / L, citric acid 1.15g / L, pH adjusted to 6.5.

[0029] Embodiment 2:

[0030] A method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge, comprising the following steps:

[0031] 1. Take 1L of fresh papermaking sludge, add 0.1% of the dry weight of the sludge into it. Non-ionic surfactant (fatty alcohol polyoxyethylene ether), stir and ultrasonically vibrate for 30 minutes. Take the filter residue after filtering, and then dry it at 65°C to constant weight. Weigh the dry papermaking sludge and crush it into fine powder. Add 20% sulfuric acid solution by mass at an addition amount of 15ml / g, react at 100°C for 100min to obtain the hydrolyzate, and then remove the sulfate with 1M barium hydroxide. After filtering, add 3% w / v activated carbon to remove other inhibitors (furfural and lignin), filter to obtain the detoxified hydrolyzate, and use 1M sodium hydroxide to adjust the pH to 6.5 for the next step of medium preparation.

[0032] 2. Take the papermaking sludge hydrolyzate and dilute it 3 times, add 1% peptone and 1% yeast extract to the volume of the diluted hydrolyzate, sterilize it in an autoclave at 121℃ for 20min, and then cool it to obtain the fermentation medium. Inoculate the xylem-Glucanacetobacter refrigerated in a 4℃ refrigerator into a fresh plate medium, culture it in a 30℃ constant temperature incubator for 48h until a single colony grows on the plate, and use an inoculation loop to pick the single colony on the plate medium into 50ml of seed medium under sterile conditions, and culture it at 30℃ and 200rpm for 24h to obtain the seed liquid. Inoculate the seed liquid into the 3-fold diluted fermentation medium at a 10% inoculum amount, and culture it at 30℃ for 7d. Take out the bacterial cellulose from the fermentation medium and place it in a 0.2M sodium hydroxide solution and heat it in a 90℃ water bath for 2h. Then adjust the pH to neutral with acetic acid and wash it with deionized water several times to obtain purified bacterial cellulose. Among them, the configuration of the seed culture medium: glucose 20g / L, peptone 5g / L, yeast extract 5g / L, and the pH was adjusted to 6.5; the configuration of the plate culture medium: glucose 20g / L, peptone 5g / L, yeast extract 5g / L, agar 20g / L, and the pH was adjusted to 6.5.

[0033] According to the above method, the bacterial cellulose yield of 5g dry weight paper sludge is 10g / L, and the tensile strength is about 0.04Mpa. Under the same culture conditions, the yield of xylem-Gluconacetobacter in glucose reference medium is 12g / L, and the tensile strength is about 0.03Mpa. The yield and performance of the two are equivalent. The configuration of glucose reference medium: glucose 20g / L, peptone 5g / L, yeast extract 5g / L, sodium dihydrogen phosphate 2.7g / L, citric acid 1.15g / L, pH adjusted to 6.5.

[0034] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge, characterized in that: The following steps are involved: Step 1, adding a nonionic surfactant to the wet papermaking sludge, stirring evenly and drying to obtain dry papermaking sludge; Step 2: hydrolyzing the dry papermaking sludge by an acid-heat method to obtain a papermaking sludge hydrolyzate; Step 3: remove acid radicals and other inhibitors in the hydrolyzate, adjust the pH to 6.0-6.8, dilute the hydrolyzate, add a nitrogen source to the diluted hydrolyzate, sterilize it and use it as a fermentation medium for Acetobacter xylinum, and inoculate Acetobacter xylinum to produce bacterial cellulose.

2. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 1, characterized in that: In step 1, the nonionic surfactant is fatty alcohol polyoxyethylene ether, and the addition amount is 0.1% to 0.5% of the dry papermaking sludge.

3. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 1, characterized in that: In step 1, the wet papermaking sludge to which the nonionic surfactant is added is stirred evenly and then ultrasonicated for 30 to 60 minutes, the filter residue is filtered and then dried at 65° C. to constant weight.

4. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 1, characterized in that: In step 2, the dry papermaking sludge is ground into powder and then sulfuric acid solution is added. The concentration of the sulfuric acid solution is 20%-35%, the addition amount is 10-20 ml / g, the temperature of the hydrolysis reaction is 90-110° C., and the reaction time is 90-120 min.

5. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 4, characterized in that: In step three, barium hydroxide is added to the hydrolyzate to remove sulfate, activated carbon is added to the filtered filtrate to remove other inhibitors, and sodium hydroxide is used to adjust the pH of the hydrolyzate after filtration.

6. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 5, characterized in that: The concentration of barium hydroxide used was 1 M, the concentration of sodium hydroxide was 1 M, and the amount of activated carbon added was 3% to 6% w / v.

7. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 1, characterized in that: In step three, the hydrolyzate is diluted 1-3 times; 1% peptone and 1% yeast extract are used as nitrogen sources based on the volume of the diluted hydrolyzate, and the sterilization temperature is 121° C. for 20 min.

8. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 1, characterized in that: In step 3, the Acetobacter xylinum seed solution is inoculated at an inoculation amount of 6-10% of the volume of the Acetobacter xylinum fermentation medium, and then statically cultured in a constant temperature incubator at 25-30° C. for 7-14 days to obtain crude bacterial cellulose.

9. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 8, characterized in that: In step three, the method for preparing the xylinum Acetobacter seed liquid is as follows: inoculate the xylinum Acetobacter into a fresh plate culture medium, culture it in a constant temperature incubator until a single colony grows on the plate, and then inoculate the single colony on the plate culture medium into a seed culture medium under sterile conditions to obtain the xylinum Acetobacter seed liquid for fermentation.

10. The method for producing bacterial cellulose by acid-thermal pretreatment of papermaking sludge according to claim 8, characterized in that: The crude bacterial cellulose is placed in a 0.1-0.2M sodium hydroxide solution and heated in a 90°C water bath for 2-4 hours, the pH is adjusted to neutral with acetic acid, and the bacterial cellulose membrane is washed several times with deionized water to obtain purified bacterial cellulose.

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