JPWO2021153585A5 - - Google Patents

Description

Fermentation production processes for chemicals using carbohydrates as raw materials are used to produce various industrial raw materials. Currently, carbohydrates derived from edible raw materials such as sugar cane, starch, and sugar beet are used industrially as raw materials for this fermentation, but the future rise in the price of edible raw materials due to the increase in the world's population, or From the ethical aspect of competition, we are developing a process to more efficiently produce sugar solution from renewable non-edible resources, i.e. cellulose-containing biomass, or efficiently converting the resulting sugar solution into an industrial raw material by using it as a fermentation raw material. The challenge for the future is to create a process to do so.

For example, in order to improve the rate of enzymatic hydrolysis of cellulose , a cellulose-containing biomass can be treated with an alkali treatment in which a cellulose-containing material is brought into contact with an alkaline aqueous solution, and a specific pretreatment that repeatedly uses the alkaline filtrate can be applied to cellulose-containing biomass. has been disclosed to contain sugar with high purity (Patent Document 1).

The degree of pulverization of the pulverized biomass obtained in step (1) is pulverized until the weight percentage (dry weight %) that does not pass through a sieve with an opening of 1 mm is about 50% or less by dry weight, preferably about 40% or more. By grinding to about 50% or less, more preferably from about 40% to about 45 % , or from about 45% to about 50%, solid-liquid separation is surprisingly improved compared to when such grinding is not done. The subsequent moisture content is reduced, thereby making it possible to reduce fermentation inhibitory substances derived from the pretreated biomass that are brought into the subsequent hydrolysis. The degree of pulverization is evaluated by drying the pulverized biomass to a moisture content of 20% or less, and then passing the pulverized biomass through a sieve with an opening of 1 mm. In this specification, the degree of pulverization may be expressed as high if the weight proportion (dry weight %) of the pulverized biomass that does not pass through a sieve with an opening of 1 mm is low. The sieving method and conditions comply with ISO 2591-1.

The alkaline concentration of the alkaline aqueous medium can be calculated from the content of alkaline substances (alkaline solid content such as hydroxide) in the alkali-containing medium. The upper limit of the alkaline concentration of the alkaline aqueous medium is not particularly limited, but is preferably 3, 2, 1.5, 1, 0.7, 0.6, 0.5, 0.4, 0.3 or 0. It is about 2% by weight, and the lower limit is preferably about 0.05, 0.1, 0.2, 0.3, 0.4 or 0.5% by weight. Further, preferable alkali concentration ranges are, for example, about 0.05% by weight or more and about 0.3% by weight or less, about 0.1% by weight or more and about 3% by weight or less, and about 0.1% by weight or more and about 2% by weight. The following more preferable ranges are about 0.1 wt% or more and about 2 wt% or less , about 0.25 wt% or more and about 1.5 wt% or less, about 0.25 wt% or more and about 1.5 wt% or less, and A preferable range is about 0.25% by weight or more and about 1.0% by weight or less.

In step (4), the cellulose- containing solid content is hydrolyzed to obtain a sugar solution. In the hydrolysis step, known hydrolysis methods such as acid hydrolysis, alkaline hydrolysis, and enzymatic hydrolysis can be applied, but it is preferable to hydrolyze the cellulose- containing solid content with an enzyme in an aqueous medium. The sugar solution obtained by such an enzymatic hydrolysis step can be obtained as an aqueous solution containing oligosaccharides and/or monosaccharides such as glucose, xylose, arabinose, galactose, xylobiose, and cellobiose.

The concentration of glucose, xylose, or xylobiose in the sugar solution obtained in step (4) is not particularly limited, and can be appropriately set by adjusting the reaction conditions of each step. Suitable glucose concentrations include, for example, about 5 g/L to about 1000 g/L, about 5 g/L to about 700 g/L, about 5 g/L to about 550 g/L, or about 10 g/L to about 550 g/L. It is below that level. Further, a suitable xylose concentration is, for example, about 1 g/L or more and about 100 g/L or less , about 1 g/L or more and about 50 g/L or less, or about 1 g/L or more and about 10 g/L or less. In addition, suitable xylobiose concentrations include, for example, about 1 g/L or more and about 100 g/L or less , about 1 g/L or more and about 50 g/L or less, about 1 g/L or more and about 20 g/L or less, or about 1 g/L or more and about 15 g /L or less.

Nanofiltration membrane or reverse osmosis membrane treatment refers to filtering the sugar solution produced in step (4) through a nanofiltration membrane or reverse osmosis membrane to remove dissolved sugars, especially monosaccharides such as glucose and xylose, It is a process in which oligosaccharides such as xylobiose and cellobiose are blocked or filtered to the non-permeable side of the membrane, and fermentation inhibitors remaining in the sugar solution are permeated as a permeate, and it can be carried out by the method described in WO2010/067785. .

Comparative Reference Example 2: Relationship between bagasse grinding degree and cellulose-containing solid moisture content during hydrothermal treatment The grinding was carried out under the same conditions as Comparative Reference Example 1, except that the screen pore diameter of the cutter mill was set to 40 mm as the grinding conditions. In addition, the pulverized biomass was dried to a moisture content of 20% to measure the dry weight percentage, and passed through a sieve with a 1 mm opening under the conditions of ISO 2591-1, and the weight percentage that did not pass was measured, and it was 50%. Further, the moisture content of the cellulose-containing solid after solid-liquid separation was 73%. The results are shown in Table 2.

Comparative Reference Example 3: Relationship between bagasse grinding degree and cellulose-containing solid water content during hydrothermal treatment The grinding conditions were the same as in Comparative Reference Example 1, except that the screen pore diameter of the cutter mill was 50 mm. In addition, the pulverized biomass was dried to a moisture content of 20% to measure the dry weight percentage, and passed through a sieve with a 1 mm opening under the conditions of ISO 2591-1, and the weight percentage that did not pass was measured, and it was 55%. Further, the moisture content of the cellulose-containing solid after solid-liquid separation was 70%. The results are shown in Table 2.

As can be seen from Table 2 , when the pretreatment is hydrothermal treatment, as the proportion (dry weight %) of the pulverized biomass that does not pass through a 1 mm sieve decreases (as the degree of pulverization increases), the cellulose content after solid-liquid separation increases. It is well known to those skilled in the art that in the treatment of wastewater with increased solid water content (%) and powder slurry, the higher the degree of pulverization of the powder, the more difficult it is to dewater (J.Soc.Powder Technol., Japan, 38, 177-183 (2001), Table 2). On the other hand, when the pretreatment is alkaline treatment, as the proportion (dry weight %) of the pulverized biomass that does not pass through a 1 mm sieve decreases (as the degree of pulverization increases), contrary to information well known to those skilled in the art, The water content (%) of cellulose-containing solids after liquid separation decreases, and by increasing the degree of pulverization of the pulverized biomass, it reduces fermentation inhibitors derived from pretreatment that are mixed in when producing sugar solution in the subsequent hydrolysis. A possibility was discovered.

Example 3: Example of producing sugar solution from bagasse (steps (1) to (5) performed)
The sugar solution obtained in Example 1 after hydrolysis in step (4) was separated into solid and liquid by centrifugation (manufactured by Saito Centrifugal Machinery Co., Ltd., 2,000 rpm), and then filtered through a microfiltration membrane (manufactured by Millipore Corporation, microfiltration membrane). After filtration using a PVDF membrane with a pore size of 0.05 μm, the sugar solution is collected as a concentrated solution through a reverse osmosis membrane (Crosslinked fully aromatic polyamide reverse osmosis membrane UTC80 manufactured by Toray Industries, Inc.), and the raw water is Water was collected as permeate so that it was concentrated to one quarter of the volume .

Claims (9)

A method for producing a sugar solution using cellulose-containing biomass as a raw material, the method comprising:
Step (1): A step of crushing the cellulose-containing biomass so that the weight percentage that does not pass through a sieve with an opening of 1 mm is 50% or less by dry weight,
Step (2): a step of contacting the pulverized biomass obtained in step (1) with an alkaline aqueous medium to obtain pretreated biomass,
Step (3): Adding water to the pretreated biomass obtained in Step (2) and performing solid-liquid separation to obtain a cellulose-containing solid content with a water content of 50% by weight or more and less than 70% by weight , and a step (4): a step of hydrolyzing the cellulose-containing solid obtained in step (3) to obtain a sugar solution;
including methods. The method for producing a sugar solution according to claim 1, wherein the step (2) is a step of obtaining a pretreated biomass by passing an alkaline medium through the pulverized biomass obtained in the step (1). Claim 1, wherein the step (2) is a step of supplying the pulverized biomass and alkaline medium obtained in the step (1) to a filter, and passing the pulverized biomass and the alkaline medium through the filter. Or the method for producing a sugar solution according to 2. The method for producing a sugar solution according to any one of claims 1 to 3, wherein the alkaline aqueous medium in step (2) is an aqueous medium containing sodium hydroxide and/or potassium hydroxide. The method for producing a sugar solution according to any one of claims 1 to 4, wherein the solid-liquid separation in step (3) is compression. The method for producing a sugar solution according to any one of claims 1 to 5, wherein the cellulose-containing biomass is bagasse. Step (5): The sugar solution obtained in step (4) is filtered through a nanofiltration membrane or a reverse osmosis membrane, the sugar solution is recovered as a non-permeate liquid, and the permeate is used as a pretreated biomass in step (3). The process of reusing water to be added to
The method for producing a sugar solution according to any one of claims 1 to 6, further comprising: A cellulose-containing solid content, which contains pulverized cellulose-containing biomass and an alkaline aqueous medium whose weight proportion that does not pass through a sieve with a 1 mm opening is 50% or less by dry weight, and whose water content is 50% by weight or more and less than 70% by weight. The cellulose-containing solid content according to claim 8, wherein the cellulose-containing biomass is bagasse.