Process for obtaining a concentrated protein-rich phase from waste products of bioethanol production

Abstract

1) A method for obtaining a concentrated protein-rich phase from residues of bioethanol production. 2.1) Previously, the separation of a protein-rich phase from whole stillage from bioethanol production has been achieved either by the addition of chemicals or by process steps that are complex in terms of equipment and/or energy. 2.2) Whole stillage from bioethanol production is fed to a solid-liquid separation, and the liquid phase (thin stillage) resulting from this is partially returned to the mashing process. This recirculation increases the raw protein content in the process. Part of the thin stillage is diluted and fed to a simple separation process without the addition of chemicals and temperature treatment, with a protein-rich phase being obtained. 2.3) A protein-rich phase is obtained from residues of bioethanol production.

Claims

1. A method for obtaining a concentrated protein-rich phase from waste products of bioethanol production, characterised in that: a) a ground cereal is mashed in a mashing process to produce a mashed ground cereal before fermentation; b) fermented mash resulting from the fermentation of the mashed ground cereal is fed to a distillation process which produces whole stillage as waste product; c) the whole stillage from b) is fed to a solid-liquid separation to produce a liquid phase (thin stillage) and a solid, and the resulting solid is discharged from the method; d) the thin stillage is partially returned to the mashing process, with at least 0.15 kg thin stillage DM per kg of cereal DM being returned and the raw protein content of the thin stillage being increased by recirculating the thin stillage to the mashing process; and e) at least part of the thin stillage is diluted with an aqueous process liquid and fed to a further separation process, an aqueous phase is separated in this further separation process (the clear phase) containing and contains predominantly the dissolved dry matter, and the concentrated protein-rich phase is produced in this further separation process (the concentrate) and contains predominantly protein-rich suspended dry matter.

2. The method according to claim 1, characterised in that the mashing process is carried out with at least 0.25 kg thin stillage DM per kg of cereal DM.

3. The method according to claim 1, characterised in that a pH value<4.0 is maintained throughout the method.

4. The method according to claim 1, characterised in that a cold mashing process precedes the fermentation.

5. The method according to claim 1, characterised in that the solid-liquid separation of the whole stillage takes place in a filter press or in a decanter.

6. The method according to claim 1, characterised in that, by the partial recirculation to the mashing process, the raw protein content of the thin stillage is increased by at least 5% rel. compared to the raw protein content of the cereal less starch.

7. The method according to claim 1, characterised in that the partial dilution of the thin stillage is carried out with a process liquid, such as condensate selected from the group consisting of condensates from a thin stillage evaporation, condensates from a drying process, and lutter water from the distillation process and water.

8. The method according to claim 1, characterised in that the thin stillage is diluted with a process liquid in a ratio of at least 1:1 before the further separation in e).

9. The method according to claim 1, characterised in that the further separation of the diluted thin stillage into the clear phase and the concentrate is performed with the aid of a separator and takes place at least at 2800×g.

10. The method according to claim 1, characterised in that, by a targeted use of enzymes selected from the group of cellulases, hemicellulases, trehalases, xylanases, amylases, lipases, phytases and combinations thereof, non-protein-containing suspended substances are cleaved and dissolved.

11. The method according to claim 1, characterised in that the concentrate has a raw protein content increased by at least 15% rel. compared to the thin stillage.

12. The method according to claim 1, characterised in that the concentrate has a raw protein content of at least 44% DM.

13. The method according to claim 1, characterised in that the clear phase is at least partially returned to the process.

14. The method according to claim 1, characterised in that the concentrate is at least partially used directly as a high-quality protein feed or is fed to further treatment steps.

15. The method of claim 2, characterised in that the mashing process is carried out with at least 0.35 kg thin stillage DM per kg of cereal DM.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 SHOWS THE DISTRIBUTION OF THE RAW PROTEIN IN THE INDIVIDUAL PARTICLE SIZE FRACTIONS USING THE EXAMPLE OF A WHOLE STILLAGE FROM THE PRESENT PROCESS

(2) FIG. 2 SHOWS AN EXAMPLE OF STANDARDISED RAW PROTEIN CONTENT OF CEREAL LESS STARCH AND OF A THIN STILLAGE WITH A CONSTANT RECIRCULATION OF 0.19 KG THIN STILLAGE DM/KG CEREAL DM (STANDARDISED TO RAW PROTEIN CONTENT OF CEREAL LESS STARCH)

(3) FIG. 3 SHOWS A FLOW CHART OF A POSSIBLE EMBODIMENT ACCORDING TO THE INVENTION

(4) FIG. 4 SHOWS A FLOW CHART OF A POSSIBLE EMBODIMENT ACCORDING TO THE INVENTION IN THE FORM OF A TWO-STAGE SEPARATION

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Practical Example 1

(5) The possibility of a technical implementation of the method is illustrated below by the recovery of a concentrated protein-rich phase from triticale-rye thin stillage (FIG. 3).

(6) A triticale-rye mixture contains the following ingredients:

(7) TABLE-US-00002 TABLE 2 Dry matter 85% OS Starch 67% DM Raw protein 11% DM OS - original substance

(8) If the starch were fully converted, the raw protein content would be 34% DM.

(9) Before fermentation, a triticale-rye mixture is dry-ground and mixed with 0.24 kg thin stillage DM per kg of cereal DM and water in a ratio of 1:4.0, i.e. one part cereal and 4 parts liquid. The enzymatic digestion of the mash takes place at approximately 47° C. By adding the yeast the fermentation is started, which takes about 60 hours. The ethanol produced is then separated from the fermented mash in the distillation.

(10) The resulting whole stillage is fed at a mass flow rate of approximately 71 t/h to a solid-liquid separation in a decanter. The separation particle size of the decanter is approximately 250 μm. All particles larger than 390 μm are completely separated in this step and contain 5% of the raw protein originally present in the whole stillage. About 76% of the protein-rich particles<50 μm remain in the thin stillage. The mass flow rate of the separated solids which are discharged is approximately 7 t/h; the thin stillage mass flow rate is approximately 64 t/h.

(11) The thin stillage has a DM content of approximately 13%, of which about half is present in suspended or dissolved form. The average particle size is 38 μm; ¾ of the particles are smaller than 20 μm. The particles<20 μm contain about 90% of the raw protein.

(12) A thin stillage mass flow rate of 31 t/h is returned to the mashing process (shown as dashed lines in FIG. 3); 19 t/h go into evaporation. The remaining thin stillage is fed into a collecting tank and from there into a stirred tank into which the condensate from the thin stillage evaporation is simultaneously fed (shown as dashed lines in FIG. 3). The thin stillage and the condensate are mixed in the ratio 1:1.

(13) The diluted thin stillage, referred to hereinafter as the inflow, has a temperature of 50° C. and is first pre-cleaned in a rotary brush screen to separate coarse particles and impurities. The gap width of the filter screen is 0.4 mm.

(14) With a mass flow rate of 12 t/h the pre-cleaned inflow is led to the nozzle separator. This contains 12 nozzles, which are arranged on the underside of the drum and have a diameter of 0.7 mm. Separation of the inflow in the separator takes place at approximately 5500×g, with the clear phase flowing out via the gripper in the upper part. The solids collect at the edge and are discharged through the nozzles at the underside, limiting the concentrate flow and thus ensuring enrichment.

(15) Table 3 compares the mass flow rates, DM and raw protein contents of the individual flows of the nozzle separator. The raw protein content of the concentrate shows that the protein-rich particles could be successfully enriched under the stated process conditions. The yield of raw protein in this example is 47%.

(16) TABLE-US-00003 TABLE 3 Inflow Clear phase Concentrate Mass flow rate [t/h] 12.0 9.8 2.2 Dry matter content [wt %] 6.2 4.6 13.3 Raw protein content [% DM] 41 36 50

(17) The separated clear phase is returned to the evaporation (shown as dashed lines in FIG. 3) and the resulting condensate is again available as a dilution medium for the thin stillage. The protein-rich concentrate produced is collected and used either directly or after evaporation or spray drying as a high-quality protein feed.

(18) Compared with animal feed currently available on the market, which has been produced from residues of bioethanol production (Table 4), the concentrate has a considerably higher value due to the significantly increased raw protein content.

(19) TABLE-US-00004 TABLE 4 DM Raw protein content [% DM] [% DM]. ProtiGrain ®.sup.(1) 90 29 Wheat/barley Dried Distillers Grains 90 38 with Solubles .sup.(2) Pressed whole stillage.sup.(3) 34.5 27 GrainPro.sup.(4) 27 37 .sup.(1)http://www.cropenergies.com/de/Downloads/Broschueren/Broschueren-Dateien/Datenblatt_Protigrain/DatenblattProtiGrain_Juli_2016.pdf (retrieved 13 Mar. 2019) .sup.(2) https://www.lfl.bayern.de/mam/cms07/ite/dateien/trockenschlempe_merkblatt.pdf (retrieved on 13 Mar. 2019) .sup.(3)http://futtermittel-getreidetechnik.de/pages/produkte/press-schlempe.php (retrieved on 13 Mar. 2019) .sup.(4)https://vantriest.eu/de/product/grain-pro-3/ (retrieved on 13 Mar. 2019)

Practical Example 2

(20) A further possibility of a technical implementation of the method will be illustrated hereinafter by the recovery of a concentrated protein-rich phase by a two-stage separation in a nozzle separator (FIG. 4).

(21) Thin stillage from the ethanol process is mixed in a stirred vessel with condensate from the thin stillage evaporation in a ratio of 1:1. This stream, referred to as inflow 1, is fed to the nozzle separator with a mass flow rate of 10.8 t/h and separated at approximately 5500×g into 8.4 t/h clear phase 1 and 2.4 t/h concentrate 1.

(22) The relevant measured quantities of the streams of the 1.sup.st separation stage are listed in Table 5. The yield of raw protein is 50%.

(23) TABLE-US-00005 TABLE 5 Clear Inflow 1 phase 1 Concentrate 1 Mass flow rate [t/h] 10.8 8.4 2.4 Dry matter content [wt %] 8.0 6.2 14.3 Raw protein content [% DM] 41 34 52

(24) The concentrate 1 is first collected in a receiver tank, since a minimum supply to the nozzle separator is required for the 2.sup.nd separation step. When the tank is filled, the concentrate 1 is fed into a stirred tank where it is diluted with condensate from the thin stillage evaporation in a ratio of 1:1. This stream, referred to as inflow 2, is fed to the nozzle separator at a mass flow rate of 10.8 t/h and separated at approximately 5500×g into 8.4 t/h clear phase 2 and 2.4 t/h concentrate 2. The relevant measured quantities of the streams of the 2.sup.nd separation stage are listed in Table 6. The yield of raw protein in the 2.sup.nd separation stage is 62%.

(25) TABLE-US-00006 TABLE 6 Clear Inflow 2 phase 2 Concentrate 2 Mass flow rate [t/h] 10.8 8.4 2.4 Dry matter content [wt %] 6.8 3.7 17.4 Raw protein content [% DM] 53 47 58

(26) The raw protein content in concentrate 2 shows that a two-stage separation results in a significant improvement of the protein product. The total yield of raw protein by a two-stage separation in this example is 31%.

Practical Example 3

(27) A further possibility of carrying out the method on a laboratory scale is illustrated below by the recovery of a concentrated protein-rich phase starting from a concentrate that was produced as in Example 1 and then treated enzymatically.

(28) The concentrate used has a DM content of 13.7% and a raw protein content of 48% DM. For the enzymatic treatment, 250 g of the concentrate is weighed into a 500 ml fermenting flask. The enzyme used is a preparation with cellulase, hemicellulase and xylanase activity in a dosage of 0.1% DM. In the reference batch no enzyme is added to the concentrate. The fermenting flasks are sealed with a fermentation tube and incubated in a shaker at 150 rpm and 33° C. for 72 h. At the end of the incubation period, 100 g of the treated material (from the flask with enzyme or from the flask without enzyme) are mixed with 100 g of tap water, previously temperature-controlled to 33° C., and then centrifuged at 4770×g for 15 min. The raw protein content of both pellets is determined.

(29) For comparison, the concentrate, which served as starting material for the experiments, is temperature-controlled to 33° C. and diluted with tap water in a ratio of 1:1 as described above and centrifuged for 15 min at 4770×g. The resulting pellet is analysed.

(30) The DM and raw protein contents of the pellets are summarised in Table 7.

(31) TABLE-US-00007 TABLE 7 Pellet from Pellet from Pellet from treatment treatment concentrate without enzyme with enzyme Dry matter [wt %] 25.0 25.2 24.4 content Raw protein [% DM] 56 56 61 content

(32) The enzymatic treatment significantly increases the raw protein content in the pellet. The DM content is reduced because the enzymes cleave and dissolve undissolved non-protein-containing substances, which remain in the supernatant after centrifugation.