FI72533B - FOERFARANDE FOER UTVINNING AV MONOSACKARIDER SAMT ANLAEGGNING FOER GENOMFOERANDE AV FOERFARANDET. - Google Patents

Description

72533

The present invention relates to a process for recovering monosaccharides from a cellulosic material by cellulase digestion, and optionally to recover the products obtained from these monosaccharides by fermentation with an aqueous process, the process comprising reacting the cellulose , which is between room temperature and about 50 ° C. The invention also relates to an apparatus according to the preamble of claim 10 for carrying out such a process using a cellulosic feedstock comminution or sterilization unit and a mixer provided with an enzyme solution addition tube.

The enzymatic production of sugar from cellulose is known from U.S. Patents 3,972,775 and 4,097,333, of which 3,972,775 relate both to the production of the enzyme by growing microorganisms and to the hydrolysis of the cellulosic material by the produced enzyme. The hydrolysis or degradation of the cellulose is performed in a single step. According to U.S. Pat. No. 4,097,333, the cellulosic material is contacted with ethylene, as this treatment increases glucose yield by enzymatic hydrolysis.

Multistage hydrolysis of a cellulosic material is in turn known from Wilke, C.R. et al., Bio-technol. Bioeng. 2_3 (1981) 163-183, and Ghose, T.K. and Ghosh, P., J. appi. Chem. Biotechnol. 2j [(1978) 309-320. According to Wilke et al., The cellulosic material is pretreated with acid to extract the pentoses, after which the solid is separated, washed and then contacted countercurrently with the enzyme- and sugar-containing solution from the hydrolyzer, whereupon the enzyme is adsorbed.

72533 The hydrolyser used consists of five mixed extractors. The pretreated solid is introduced as a 5% by weight solution into the hydrolyzer. The enzyme-containing sugar solution obtained after separation of the solid can be partially returned to the hydrolyzer, the rest of the solution being evaporated to dryness after adsorption of the enzyme. The enzyme-free sugar solution from the hydrolyzer is subjected to alcoholic fermentation. The cellulose degrading enzyme is obtained by culturing the strain Trichoderma viride QM 9414 in a two-stage fermentation system. The enzyme is added in the form of an aqueous solution directly to the hydrolyzer.

T. K. The multi-step hydrolysis according to Ghoses and P. Ghosh closely resembles the solution of Wilke et al. Described above. Thus, the ground newsprint is mixed countercurrently, in three steps, with a hydrolyzate obtained from a 5-part hydrolyzer, whereby the solid is separated after each mixing step. The solid from the final mixing step is fed to the hydrolyser with the enzyme solution prepared in the four fermentors.

The difficulty in the technical use of enzymatic digestion for the preparation of monosaccharides and possibly their fermentation products, such as alcohols and proteins, is mainly due to the very low concentration achieved by microbiological degradation - eg up to a few% hydrolysed from cellulase for 48 hours. and thus the energy costs required for concentration or purification are far too high. Thus, when it has been technically desired to produce sugars and further alcohol from cellulosic starting materials, the decomposition has hitherto been carried out with the aid of acids, mostly using high pressures and temperatures. These methods are also very energy intensive and involve acid recovery problems.

Il 3 72533 The object of the present invention is to avoid these disadvantages and difficulties and to provide a continuous, technical and improved method of utilizing cellulosic raw materials of the type described in the introduction, operating at room temperature or at slightly elevated temperature, requiring relatively little energy, avoiding high pressure equipment, using cheap starting materials or waste and do not burden the environment.

The task is solved by carrying out the reaction in several reaction steps and after each reaction step the enzyme and sugar solution are separated from the solids, the solids are transferred to the next reaction step after washing the formed carbohydrates, the enzyme and sugar solutions obtained from the reaction steps are exploiting micro-organisms.

Thus, the enzymatic hydrolysis is carried out in several stages, i.e. at least in two stages, but preferably in no more than six stages. The material to be hydrolysed is passed through all successively connected reaction steps and the carbohydrates formed are washed off between the individual steps each time. This avoids the inhibition of hydrolysis caused by too high a sugar concentration and, according to the invention, achieves a faster reaction and a better efficiency compared to the one-step process. After the final reaction step, the non-hydrolyzed solid is separated from the solution, washed and transferred to an incinerator or for use elsewhere.

It is preferred to sterilize the cellulosic feedstock before it is reacted with the aqueous cellulase-containing solution. Sterilization can be accomplished by ozonation, addition of a biocide such as sodium pentachlorophenol, or by steam.

It is preferable to grind the suspension obtained from the reaction steps to a slurry before the solid is separated from the enzyme-containing solution. By means of this grinding, a new surface of the cellulosic material is exposed to the action of the enzyme, and in addition the sugars which are still formed as oligomers can be washed away better.

Before proceeding to the next reaction step, it is preferable to mix further fresh cellulase solution with the separated solid, unless the solid is then from the last reaction step. The advantage of this embodiment is that it accelerates the hydrolysis.

It is expedient to decompose the enzyme and sugar-containing solution obtained from the reaction steps and separated from the solids by means of an enzyme immobilized completely as monosaccharides, and it is preferable to use an immobilized β-glucosidase as the immobilized enzyme. In immobilized enzymes, the enzyme is attached to a carrier, e.g., a polyacrylamide gel, so that it remains fully active and is not washed away with the contact solution.

In order to prepare monosaccharides in accordance with a preferred embodiment of this invention, the enzyme and sugar-containing solutions are partially recycled to the individual reaction steps for dilution, again removed from the reaction steps with the reaction products and partially mixed with fresh cellulosic material so that the enzyme is adsorbed to the cellulosic material. . One of the main components of the resulting sugar-containing solution is glucose, the concentration of which can be increased in this way. Moreover, the enzyme- and sugar-containing solutions do not contain cellobiose, so the recycled part does not prevent hydrolysis. The sugar solution released from the enzyme can be diverted to another use. The cellulosic material and the enzyme adsorbed thereon are returned to the process as starting material.

Il 5 72533

In order to prepare fermentation products such as ethanol according to a preferred embodiment of this invention, after fermentation of the enzyme and sugar solutions, the microorganisms are separated from the fermentation liquid, the fermentation liquid is partially returned to the individual reaction steps for dilution, again removed from the reaction so that the enzyme is adsorbed on the cellulosic material and thus separated or can be recovered, and the fermentation products can be recovered in pure form from the liquid containing the fermentation products by distillation or rectification.

In this embodiment, it is not necessary to separate the cellulase from the sugar solution before the fermentation step. The method can also be carried out for the purpose of producing proteins, so that mainly biomass is formed, i.e. e.g. yeast cells, fungal mycelium or other microorganisms, and the formation of other fermentation products is more or less in the background.

The microorganisms used in the fermentation step are separated, e.g. by centrifugation, and returned to or removed from the system. The biomass thus obtained can be used as an additive in animal feed.

It is convenient to keep the solids content at about 10% by weight in the individual reaction steps. When the enzyme-sugar-containing solutions or the liquid containing fermentation products are partially returned to the sequentially arranged reaction steps, the concentration of sugars or fermentation products therein increases.

It is preferable to return the liquid containing enzymatic or sugar-containing solutions or fermentation products through the inlets to the bottoms back to the individual reaction steps because a suspension of a cellulosic feedstock such as wood, straw or 6,72533 waste paper with a solids content of 10% by weight is difficult to pump. , and in this way the removal of solids from the individual reaction steps is considerably facilitated.

Apparatus as described in the introduction for carrying out the process according to the invention further comprises at least two hydrolysis tanks, a solids separator, a centrifuge, and possibly a fermentation tank and a distillation or rectification device connected to them - possibly via a mixing tank and a mill. The apparatus is characterized in that each of the at least two hydrolysis tanks can be connected via a pipeline to the mixer on the one hand and to the solids removal member of the centrifuge on the other hand. The bottom of each hydrolysis tank can further be connected to a centrifuge via a suspension collection line, possibly with a mixing tank and a mill stern connected between the collection line and the centrifuge, and the liquid portion of the centrifuge is also connected.

The invention is illustrated in more detail below by means of a flow chart and an example.

The cellulosic feedstock is first fed to a comminuting device 1 and then to a twin roll mill 2. From the mill the material is transferred to a mixer 3 provided with a sterilant supply pipe 4. The material containing the sterilizing agent is transferred to a sterilizing tank 5 where it remains for a certain time. The sterilized material from this container is passed along a feed pipe 6 to a second mixer 7, where a cellulase-containing aqueous solution is added along the pipe 8. From the mixer 7, material is fed via a pipe 10 to the individual reaction steps or hydrolysis tanks 9. The co-assembly tube 11 removes the suspension from the individual hydrolysis tanks 9 to the mixing tank 12, to which further

II

7 72533 supply pipes for ozonated fresh water (13), for waste water (14) and for returning liquids (15) containing enzyme and sugar-containing solutions or fermentation products. From the tank 12 the suspension is transferred to a mill 16 where it is ground to a slurry. The solid is then separated from the solution by means of a centrifuge 17. The solid is pretreated in a heat exchanger 18, passed through a second mixer 19, where optionally fresh cellulase solution is added via line 8, and passed through line 10 to the next hydrolysis tank 9. The solids still in the last hydrolysis tank are removed along the outlet pipe 20. In order to reduce the loss of carbohydrate or alcohol, the material from the last hydrolysis tank can be led along the pipe 20 'to the mixing tank 12 and washed there with clean water.

The liquid portion from the centrifuge 17 is first fed to a reactor 21 filled with immobilized enzyme and then via tubes 22 and 15 for partial dilution to individual hydrolysis tanks or mixing tank 12 or via tube 15 to mixing tank 23 to which cellulosic material 5 can be added. the substance is separated from the liquid by a centrifuge 25, from which the cellulase-loaded solid is passed to a mixer 7 and the resulting enzyme-free sugar solution is discharged via a pipe 26 out of the plant.

Alternatively, the liquid part from the centrifuge 17 can be led downstream of the reactor 21 to a fermentation tank 28 provided with a microorganism feed pipe 27. After a certain residence time, the fermentation product is transferred to a separator, e.g. a centrifuge 29, where the biomass is separated from the fermentation liquid. The biomass can be returned via line 27 back to the fermentation tank or removed from the plant via line 30. The liquid containing the fermentation product is first introduced into an intermediate tank 31, from where it is led by a pump 32 via a pipe 15 partially 8 72533 back to individual hydrolysis tanks 9 or to a mixing tank 12 for dilution or enzyme recovery to a mixing tank 23. to the mixing device 33, in which the fermentation products contained in the liquid, such as ethanol, pig oil and glycerin, are separated from each other. The fermentation products are removed along pipes 34, 35, the resulting waste water is either fed to a mixer 7 or a mixing tank 12 for dilution or it is removed from the plant via a pipe 36.

Example Waste paper containing 1000 kg of dry matter was shredded and sterilized for 20 min. At 120 ° C, 8950 l of water were added, the pH was adjusted to 4.8 and 50 l of enzyme suspension with a cellulase activity of 107 FPU (FPU = filter paper units, before FPD activity units, cf. N. Toyama, Advances in Enzyme Hydrolysis of Cellulose and Related Materials, ET Reese, Ed. Pergamon Press, London 1963, p. 235). Thus, the solids content of the suspension was about 10% by weight. The entire suspension was passed through 6 reaction steps or hydrolysis tanks, each with a residence time of 8 hours.

Between the individual hydrolysis steps, the formed carbohydrates were washed away and the solutions were combined. For washing, the solutions were recycled each time and finally washed with clean water. The pooled solutions with a volume of 15,000 L contained 323 kg of reducing sugar, of which 221 kg was glucose. Mannose and xylose were still present.

When sugar was used with yeast, 109 kg of ethanol were obtained. The solution still contained 7 · 106 FPU of enzyme. The non-hydrolyzed waste paper was 677 kg.

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Claims (10)

72533 A process for recovering monosaccharides from a cellulosic material by cellulase digestion, and optionally for recovering products derived from monosaccharides by fermentation, which comprises reacting a comminuted cellulosic feedstock with an aqueous solution containing cellulase at ambient pressure between about 50 ° C and room temperature. characterized in that the reaction is carried out in several reaction steps and after each reaction step the enzyme and sugar-containing solution is separated from the solid, the solids are transferred to the next reaction step after washing the formed carbohydrates, the enzyme and sugar solutions obtained from the reaction steps are organisms. Process according to Claim 1, characterized in that the cellulosic feedstock is sterilized before it is reacted with a cellulase-containing aqueous solution. Process according to Claims 1 and 2, characterized in that the suspension obtained from the reaction step is ground in a slurry-like manner before the solids are separated from the enzyme- and sugar-containing solution. Process according to Claims 1 to 3, characterized in that a fresh cellulase solution is mixed into the solid before being passed on to the next reaction step. Process according to Claims 1 to 4, characterized in that the enzyme- and sugar-containing solution obtained from the reaction steps and separated from the solid is completely decomposed into monosaccharides by means of an immobilized enzyme. 10 72533 Process according to Claim 5, characterized in that immobilized β-glucosidase is used as the immobilized enzyme. Process for the recovery of monosaccharides according to Claims 1 to 6, characterized in that the enzyme- and sugar-containing solutions are partially recycled to the individual reaction steps for dilution, removed again from the reaction steps with the reaction products and mixed with fresh cellulosic material in part so that the enzyme material and thus separates or can be recovered. Process for recovering fermentation products according to Claims 1 to 6, characterized in that, after fermentation of the enzyme- and sugar-containing solutions, the microorganisms are separated from the fermentation broth, the fermentation broth is partially returned to the individual reaction steps for dilution, removed from the reaction steps and mixed with fresh cellulosic material in part so that the enzyme is adsorbed on the cellulosic material and thus separated or can be recovered, and the fermentation products can be recovered in pure form from the liquid containing the fermentation products by distillation or rectification. Process according to Claims 7 and 8, characterized in that the liquid containing enzyme- or sugar-containing solutions or fermentation products is returned to the individual reaction steps via the feed openings in the bottoms of the tanks. Apparatus for carrying out the method according to claims 1-9, comprising a cellulosic starting material comminution device (1), a comminuted starting material sterilization unit (3, 5), a mixer (7) for mixing sterilized comminuted material via a pipeline (8) with 11 72533 feeds and possibly a fermentation tank (28) and a distillation or rectification device (33), characterized in that each of the at least two hydrolysis tanks (9) can be connected via a pipeline (10) to a mixer (7) and a centrifuge (17). ) to the solids removal member that the bottom of each hydrolysis tank (9) can be connected to a centrifuge (17) via a suspension collection line (11), optionally connecting a mixing tank (12) and a mill (16) between the collection line (11) and the centrifuge (17). ) stern, and that the discharge pipe of the liquid part of the centrifuge (17) is connected to the pipeline (22) and the supply pipe (15). ) can be connected to each hydrolysis tank (9) as well as to the fermentation tank (28). 12 72533