BR102012019454A2 - SEPARATION AND SELECTION PROCESS FOR ALCOHOLIC FERMENTATION Yeast - Google Patents

Abstract

YEAST SEPARATION AND SEALING PROCESS FOR ALCOHOLIC FERMENTATION. A yeast separation and selection process for alcoholic fermentation is described, which comprises, after the first centrifugation in (6), sending the separated wine to a lung tank (13) and from there via L14 to the process (14) of series centrifugations with at least two centrifugations increasing from at least 400 rpm to 5000 rpm where the supernatant from each centrifugation becomes the next centrifugation load and the precipitate is collected, obtaining young yeasts being returned after dilution with water and fermentation, the young yeasts separated and selected and fermentation products, young yeasts being returned after dilution with water and conventional treatments for fermentation tanks (Fr). After distillation, the separated vinasse (17) has a lower organic material content than the vinasse resulting from state of the art industrial ethanol production processes that use a single centrifugation.

Description

Yeast Separation and Selection Process for

FIELD OF ALCOHOLIC INVENTION FIELD

The present invention belongs to the field of yeast sorting and selection processes useful for the production of industrial ethanol, more specifically to a yeast sorting and selection process which employs serial centrifugations for the best use of young yeasts which are inserted into the fermentation system of alcoholic fermentation for the production of industrial alcohol 10 rather than being mixed with the stream of vinasse to be discarded.

BACKGROUND OF THE INVENTION

Ethanol has been used in recent years as an important alternative and renewable energy source to replace the 15 fossil fuels. This biofuel can be produced from the fermentation of maize, barley, wheat, sugar beet and cane. Among these, the sugarcane crop, widely cultivated in Brazil, emerges as the most economically viable raw material, because besides being rich in fermentable sugars, is greatly favored by the 20 climatic and geographical conditions of our country.

Brazil pioneered the adoption of a national sugarcane ethanol production program (Proálcool) as an alternative energy source after the first oil supply shock during the 1970s. Today Brazil is emerging as the main country to benefit from the expectation that several other countries will adopt sugarcane ethanol as a substitute for fossil fuels.

Industrial ethanol is obtained mainly through fermentation, which occurs in fermentation vats after the addition of a mixture composed of must (sugar cane juice or diluted syrup) and yeast. After the fermentation is finished, the fermented broth is centrifuged to separate the wine (fermented must) from the yeast milk, the name given to the yeast broth leaving the centrifugation. The first goes to the distillation towers while yeasts 5 return to the fermentation process. After distillation, the vinasse (ethanol distillation residue) is distributed in the sugarcane crop, as it has an important value as a fertilizer (potassium source) in the sugarcane plantations.

Already the yeast milk undergoes treatment with sulfuric acid to reduce the number of contaminating bacteria and returns to the fermentation vessel, in which will be added a new load of must for a new fermentation cycle.

This process can happen both continuously and in batch form.

In continuous fermentation the volume of yeast and must is

controlled at the beginning and end of the process so as to maintain a balance between the amount of fermentable sugar and the yeast population.

In the batch process, all the must is fermented and then centrifuged.

Figure 1 is a flow chart illustrating the continuous process of industrial production as currently practiced in the art.

According to this Figure, the first furnace (1) is fed (Fa) with diluted molasses (Fo) to approximately 10% sucrose. In the same oven are added yeasts (Fr) that will convert sucrose into ethanol.

As fermentation occurs, all liquid is transported to other vats, where fermentation continues to decrease sugar concentration and increase ethanol concentration (L2aL4a). At all stages the temperature of the drums must be controlled to remain close to 30 ° C (1a-4a).

At the end of the fermentation process, the fermented medium (L5, 5) is centrifuged (L6, 6) for the separation of yeast milk 5 (L10) from the delured wine (L7, 7) and will be taken to the distillation towers. (L9) in which ethanol distillation occurs (9) and vinasse production (L8, 8) which is used as a product for fertilization of planted areas.

The yeast milk is sent to treatment tanks (10) in the LO which is diluted with water (H2O) and an acid treatment (H +) before returning to the process (Fr).

The reuse of yeast is an economically important procedure for the mill and one of the main differentials between Brazil's production and other world producers, which do not normally operate with the yeast crop recycling. This is because the production of a new starter yeast with the proper amount of cell mass would result in high sugar consumption, which makes the process slow and increases production costs.

An important observation is that although the original yeast 20 is inoculated at high concentrations, in some plants it can be replaced by wild yeast during the fermentation process, which remains until the end of the season. In many cases, this substitution was not even noticed, and there was no drop in plant productivity, possibly because the “invasive” yeasts were better adapted to fermentation conditions.

Over the past few years, several research groups have endeavored to isolate yeast strains that persist throughout fermentation. A common feature between selected yeast strains and wild and dominant yeast strains is that they have a higher cell multiplication rate than the other yeast strains that may be present in the fermentation vessel, which favors the dominance of the fermentative medium by these strains. .

This increase in yeast proliferation, coupled with the implementation of asepsis techniques, reflected in a significant increase in yeast mass at the end of the fermentation process, and in obtaining much more concentrated yeast milk, making the procedure common. "bleed", in which a quantity of yeast is removed to maintain the optimal cellular concentration of yeast during the fermentation process.

When “bled”, this surplus of yeast is dried and marketed as an ingredient for animal feed. Data collected from various plants show that for each 1.0 m3 of ethanol produced it is possible to produce 20.0 kg of dry yeast.

The centrifugation of the fermented must still allows the loss of

important amounts of yeast for the wine to be distilled. Analyzes performed on “delugurated” (centrifuged) wine show that even after centrifugation, a high number of yeasts can still be found in this liquid, with a viable cell count of approximately 107 cells per ml of wine.

Another important observation concerns the size of the yeasts present in the “delugurated” wine. The cells of these yeasts are smaller than those present in yeast milk from the first centrifugation.

This information leads to the assumption that yeast

found in wine are younger than yeast milk originated in the first centrifugation.

As widely known in the literature, yeast can divide sexually or asexually. In asexual reproduction, which is the main form of reproduction found in fermentation vats, cells divide by budding (Figure 2A). In this context, your age can be measured according to the scars observed on your cell wall (Figure 2B).

Thus, the greater the number of scars, the older the

microorganism and, consequently, its fermentative potential.

Thus, the daughter yeast that springs from the mother yeast after cytokinesis activates several pathways of cellular metabolism that trigger intracellular processes that will activate cell growth and proliferation - making this cell eager for the fermentative process.

This size difference causes a difference in separation during the centrifugation process, causing larger and therefore older yeasts to settle more easily.

Also, at the end of the fermentation process, where stress conditions are high, some cells begin to aggregate in a process known as flocculation. This phenomenon, which is one of the most serious and detrimental problems to fermentative yield during ethanol fermentation, is due to the production of a membrane protein called floculin, which has the ability to bind to 20 carbohydrates present in the membrane of all yeast. , called Iectin (see Figure 3A, non-flocculant yeast, and Figure 3B, flocculant yeast).

With the production of these proteins, yeasts aggregate, settling more easily during the fermentation process and decreasing the efficiency of the process.

In addition, during transfer between tanks in the industrial ethanol production process, these yeasts form clumps that cause clogging in the transfer pipes, often causing the fermentation process to be interrupted, all tanks subjected to asepsis and only After this cleaning process can be restarted.

As mills in Brazil work with yeast recycling, the process currently employed favors that older and 5-flocculated yeasts are the yeasts selected to return to a new fermentative cycle, while younger cells with higher fermentative potential are smaller. they are taken along with the wine to be distilled, being killed in the heat during the distillation process to obtain ethanol and then discarded with the vinasse.

It is observed that the amount of yeast present in the vinasse is about 40.0 and 50.0 kg of yeast (dry basis) per m3 of distilled ethanol.

The presence of yeast in the wine to be distilled, and consequently in the vinasse after distillation, causes a severe aggravation of the deposition of organic material in the vinasse, contributing to a significant increase in BOD (Biochemical Oxygen Deficiency).

The levels of vinasse production are very high, exceeding the need for fertilization in the fields, so this compost has a high pollutant potential, being about one hundred times higher than domestic sewage if discharged directly into water bodies. .

In the patent literature processes that make use of a second centrifugation do so for the purpose of drying yeast for commercialization, such as that found in published Brazilian application BR9100062-9 A2.

In addition, the centrifugation process is done using the vinasse, which makes it impossible to reuse the ex-miururyanism that was killed during the distillation process. Other processes use filtration as a means of concentrating vinasse (see Brazilian published application BR0805597-1A), however again in vinasse, the same argument explained above being applicable.

In U.S. Patent 4,287,303 the inventors propose the use of

Serial centrifugation to separate solid residues from the fermentation and enrich the substrate returning to the fermenter. In this case centrifugations are always performed at the same speeds and no separation of yeast by size / viability / age / cell activity as proposed in the present invention occurs.

It would be interesting, therefore, that the technique had a yeast separation and selection process for the production of industrial ethanol with reuse of young yeasts through 15 serial centrifugation, with significant economic and environmental advantages for the plant, by reducing the BOD requirement of vinasse to be discarded in the environment.

SUMMARY OF THE INVENTION

Broadly, the improved yeast sorting and selection process for the production of industrial ethanol from a yeast-aided sucrose feedstock comprises the steps of:

a) after the first centrifugation (6), separate and store in tanks (11, 12) the oldest yeasts and

flocculated for drying, obtaining a wine;

(b) send the wine from step (a) via line (L13) to a lung tank (13);

c) from the tank (13) direct the wine via (L14) to the series centrifugation process (14), with at least two centrifugations of increasing speed of at least 400 rpm to 5000 rpm where the supernatant of each centrifugation is makes the next centrifugation load and the precipitate collected, obtaining separate and selected young yeast and fermentation products;

d) directing said young and high fermentative capacity yeast from step c) to the treatment tank (10) via (1-15) for dilution with conventional water and acid treatment;

e) returning via (L19) said diluted and treated yeasts from step d) to the fermentation tanks (Fr);

(f) by distilling off the fermentation products into wine (15), industrial alcohol (16) and vinasse (17) with an organic material content lower than that of vinasse resulting from state-of-the-art industrial ethanol production processes; use a single spin; and

g) additionally drying yeast in the tank (13) and wrapping the yeast surplus from the various centrifugations.

Thus, the invention provides an improved process of yeast sorting and selection for alcoholic fermentation which through multiple centrifugations at increasing speeds after the initial fermentation process optimizes the separation of young yeasts returning to the fermentation process, with older yeasts being left in the first centrifugations. and flocculated to be dried and marketed.

The invention further provides an improved yeast sorting and selection process for alcoholic fermentation which comprises the addition of yeasts from various centrifugations to maintain the appropriate yeast cell concentration.

The invention also provides a yeast separation and selection process for alcoholic fermentation which allows the vinasse 5 resulting from the alcoholic fermentation process using the separated and selected yeasts to have lower organic material content than that produced by state-of-the-art alcoholic fermentation processes. technique.

The invention further provides a process for sorting and selecting 10 yeasts for alcoholic fermentation which allows the vinasse resulting from the alcoholic fermentation process using the separated and selected yeasts to have reduced water body pollution power because it contains less material content. organic than vinasse produced by state of the art processes.

The invention further provides a process of separation and

Highly economical yeast selection for alcoholic fermentation for alcoholic fermentation for the production of industrial alcohol by the recovery of young yeast cells, reducing the overall cost compared to state of the art fermentative processes that practice a single centrifugation.

The invention further provides a yeast sorting and selection process for alcoholic fermentation comprising separating flocculant from non-flocculant cells.

The invention also provides a yeast separation and selection process for alcoholic fermentation directed to the selection of yeasts with high fermentative potential.

The invention further provides a yeast separation and selection process for alcoholic fermentation capable of cleaning / reducing (selecting non-flocculant cells only) flocculant and undesirable cells for the process.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying FIGURE 1 is a flowchart showing the process of industrial alcohol production by fermentation of molasses broth according to the state of the art.

The attached FIGURE 2 is a microphotograph showing the budding yeast cells. Figure 2A: cell division. Figure 2B, Yeast cell wall scars.

The attached FIGURE 3 is a schematic representation of the

aggregation (flocculation) of yeast cells. Figure 3A: Non-flocculant yeast. Figure 3B: Flocculant yeast.

The accompanying FIGURE 4 is a flowchart of the process of the invention for a fermentative process directed to the selection of yeasts with high fermentative potential.

The accompanying FIGURE 5 is a block diagram showing for the currently employed technique (1) and for the various centrifugation speeds (2-400rpm; 3-1000rpm and 4-4000rpm) the percentage of precipitated yeasts and supernatants. A: precipitated yeasts. B: 20 supernatant yeasts. Figure 5A: For flocculant yeast. Figure 5B: For non-flocculant yeasts. Figure 5C: For flocculant and non-flocculant yeasts (1: 1 w / w mixture).

The accompanying FIGURE 6 is a series of micrographs showing the appearance of the yeast precipitate and supernatant for the control condition of a 3000 rpm centrifugation and the appearance of the precipitate and supernatant for the serial centrifugation conditions of the invention. The micrographs refer to 50:50 mixtures of flocculant and non-flocculant yeasts. Figure 6A and Figure 6B precipitated and supernatant for the control condition. Figures 6C and 6D are micrographs of supernatant and precipitate respectively for yeast centrifuged at 400 rpm in the first of a series of three centrifugations according to the invention. Figures 6E and 6F are respectively micrographs of supernatant and precipitate for yeast centrifuged at 1000 rpm in 2nd centrifugation 5 according to the invention and Figures 6G and 6H are respectively micrographs of supernatant and precipitate for yeast centrifuged at 4000 rpm in 3rd serial centrifugation according to the invention. invention.

The accompanying FIGURE 7 shows two micrographs of yeast obtained in the precipitate (Figure 7A) and supernatant (Figure 7B) of non-flocculant cells centrifuged at 400 rpm.

DETAILED DESCRIPTION OF THE INVENTION

The invention is therefore a process for the separation and selection of yeasts for alcoholic fermentation from the fermentation of mash 15 in the presence of Saccharomyces cerevisiae yeasts by serial centrifugations of the fermentation broth which has already undergone a first centrifugation in a process for industrial alcohol, for the separation of young yeasts and their reinsertion in fermentation to obtain high-yield alcohol while 20 fewer yeasts are lost to the vinasse.

The present application aims at a change in the Iayout of the fermentation process currently used in industrial ethanol production plants, by aggregating a series centrifugation process, starting with lower speed centrifugations followed by 25 higher speed centrifugations prior to wine shipment. to the distillation process.

Serial centrifugation of the fermented broth allows: (i) the separation of larger and flocculated yeasts in the first centrifugation steps, cleaning the system of these microorganisms and sending them for drying; (ii) selection of young yeasts with high fermentative capacity; and (iii) reduction of organic material in vinasse contributing to a decrease in BOD.

Thus the process is able to segregate the yeast population 5 by "size / weight / age / fermentative activity".

As it is younger, yeast originated from the second centrifugation presents superior fermentative performance characteristics than yeast originated from the first centrifugation.

This yeast is sent to the treatment tanks and then to the fermentation vats, increasing the fermentative efficiency of the mills, reducing the level of infection in the vat, avoiding yeast flocculation processes, and significantly reducing the presence of yeasts. yeast in fermented wine.

As a consequence of this process, the vinasse BOD is reduced, since yeasts are reduced in this liquid, reducing the negative impact of the vinasse on the environment.

Serial centrifugation is applied with the addition of at least one further line of centrifuges over the usual number of centrifuges.

f

20 centrifuges (at least two centrifuges in series).

In the first slow centrifugation (at least 400 revolutions per minute), the older and less efficient flocculated yeasts are separated, followed by more rapid centrifugations (1000 and 2000 rpm consecutively), until the last centrifugation which, according to one mode. of this order is 4000 rpm in the experiments performed. Spin speeds of up to 5000 rpm are acceptable for the present process.

It should be clear to those skilled in the art that the exact values of spin speeds may vary within wide limits and that such values are not restricted to the experimental values cited in this report.

The concentration of young yeasts is increased according to the speed increase, and in the last centrifugation the 5 young yeasts are selected to return to the fermentative process and if necessary increased with yeasts removed in the previous centrifugations, under the condition that this should be done. from the highest to the lowest speed centrifugation.

. As the young yeasts from the last centrifugation are small in number, if not enough will be complemented by yeasts from other centrifugations, always younger than the discarded yeasts.

Advantageously, the reuse of yeasts present in the wine after the fermentation process contributes to two important aspects, the economic one (higher fermentative yield and higher production of dry yeast) and the environmental one (reduction of the vinasse BOD).

From the economic point of view, these yeasts are returned to the fermentation tanks, being used in the fermentation process in isolation, or even mixed with the previous centrifugation yeasts, always from the highest to the lowest speed, if necessary. adjust cell concentration. It is noteworthy that the older and flocculated yeasts are mostly removed in the first centrifugation.

As an innovative aspect of the present process, the new fermentative cycle is started much more vigorously, as these yeasts are younger cells with greater fermentative activity than currently used.

The utilization of the yeasts present in the centrifuged wine causes an increase of the surplus of “usable” yeasts generated in the fermentation process, which increases the amount of “bled” yeast in the process.

This additional volume can be sent for drying and sold as raw material to different industrial segments. This is already a routine and lucrative practice in ethanol mills, and the increased volume of bled yeast cream from the fermentation process makes this source of income even more important.

Experimentally, the first trials show the presence of a high number of yeasts in the wine after centrifugation used in the procedure currently employed (approximately 25% of total cells (see Figures 6 AC and centrifugation 1, Figure 5A, B and C) with a viability of approximately 90%.

On microscopic examination these yeasts are smaller and with a high degree of budding, see Figure 6B, showing that they are multiplying, unlike the yeasts coming from the first centrifugation, see Figure 6A, which are thicker and thicker. a viability of approximately 70%.

EXAMPLES

To test the efficiency of the proposed process in (i) secreting 20 younger cells and consequently with higher fermentative potential and (ii) separating flocculant and non-flocculant cells, experiments were conducted using flocculant yeast and non-flocculant yeast both separately and together using The situation currently employed for ethanol production, ie after fermentation, the cells were centrifuged at 3000 rpm (control) and using the serial centrifugation yeast separation and selection process proposed in the invention.

To obtain the experimental data, flocculant and non-flocculant yeasts were independently grown at 30 ° C for approximately 12 hours and isolated by the process currently employed and the process of the invention, either separately or mixed at a ratio of 1: 1 (w / w ).

CONTROL EXAMPLES In the control condition where only one spin is

performed at 3000 rpm, the profile is similar whether flocculant or non-flocculant. In these tests about 25% of the yeast remains in the supernatant after centrifugation.

The Control Example of Example 1 relates to flocculant yeast.

The Control Example of Example 2 concerns non-flocculant yeasts.

The Control Example of Example 3 concerns the 50:50 mixture of flocculant and non-flocculant yeasts.

The following Tables 1, 2 and 3 list the results obtained for the

control centrifugations and serial centrifugations according to the invention.

As already mentioned above in this report, the yeasts that make up the supernatant are mostly younger yeasts that end up being wasted.

Note that in serial centrifugation according to the invention, the

The supernatant of the lower speed centrifugation is re-centrifuged and therefore the sum of the percentages found in 3 and 4 in the bar graphs of Figures 5A, 5B and 5C refer to values below 100%, ie the total number of cells refers. total supernatant from previous centrifugation.

Figures 6A and 6B are micrographs of the appearance of the precipitated yeasts and supernatants respectively after centrifugation of 3000 rpm for a 50:50 mixture for flocculant and non-flocculant yeasts. As can be seen, the yeast present in the supernatant is smaller and in a budding process and is therefore younger.

EXAMPLES

Examples according to the present process involve serial centrifugations at 400, 1000 and 4000 rpm for flocculant (Example 1), non-flocculant yeast (Example 2), and 50:50 mixture of both (Example 3).

Flocculant and non-flocculant yeasts were independently grown at 30 ° C for approximately 12 hours and isolated by the process of the invention.

According to Table 1, relating to Example 1, the observed profile for flocculant yeast shows 41% of the cells that precipitate in the first 400 rpm centrifugation.

TABLE 1

FLAVORING Yeast (% OF CELLS) PRECIPITATED PRECIPITATED CONTROL 76 24 400 rpm 41 59 1000 rpm 45 14 4000 rpm 10 3 15

Table 2, relating to Example 2, shows that only 20% precipitate when non-flocculated cells are used at the same spin rate as that for flocculant yeasts.

20 TABLE 2

NON-FLOATING YeastS (% OF CELLS) PRECIPITATED PRECIPITATED CONTROL 73 27 400 rpm 20 80 1000 rpm 37 43 4000 rpm 36 7 For the serial centrifugation of the mixture in equal parts of flocculant and non-flocculant yeasts for Example 3, Table 3, 40% cell precipitation is observed in the first centrifugation (400 rpm) with a predominance of flocculant cells.

Of the remaining 60% of cells, 30% sediment in the second centrifugation (1000 rpm), again mostly being flocculant cells (Figure 6E), leaving 30% of the total cells for the next centrifugation.

TABLE 3

FLOATING AND NON-FLOATING Yeast 50:50 (% OF CELLS) PRECIPITATED SURVEY CONTROL 74 26 400 rpm 40 60 1000 rpm 30 30 4000 rpm 28 2 Supernatants re-centrifuged at 1000 rpm show the following result: a. Flocculant cells (Table 1) - Of the remaining 59% of cells - 45% sediment at this rate, with only 14% of cells remaining for the next centrifugation;

B. Non-Flocculant Cells (Table 2) - Of the 80% of supernatant cells, 37% sediment at this rate, leaving

43% of cells total for next centrifugation. These cells are the young cells that will be reused in the process. This means that even if flocculant yeasts contaminate the process they would settle in the first centrifugation steps. So the process

proposed is useful as a method of cleaning undesirable strains in the fermentation process It is noteworthy that these remaining cells are essentially non-flocculant and younger cells, showing that the proposed serial centrifugation process, besides segregating (separating) the cells by size, segregating the younger ones for recirculation, it is also able to clean (select non-flocculant cells only) flocculant and undesirable cells for the process (Figures 6F and 6G).

Regarding the analysis of isolated yeasts through the serial centrifugation process as shown in Tables 1, 2 and 3, Figure 5A, B and C and Figure 6 C to 6G, the yeasts were independently tested and mixed in equal proportion after growth.

The yeasts were centrifuged at 400, 1000 and 4000 rpm consecutively. For each of the phases - precipitated and supernatant - the cells were observed under a microscope for morphology evaluation, as well as the number of cells present - see bar graphs of Figures 5A. 5B and 5C.

Flocculant yeasts show a higher precipitation capacity at lower speeds (400 and 1000 rpm) when tested independently and also in conjunction with non-flocculant cells, see Table 1 and 3 and Figure 6A, 6C, 6D and 6E.

Regarding non-flocculant cells, the cells precipitated in the first centrifugations show different morphologies between the 5 cells of the first and subsequent centrifugations. Thus, in the first centrifugations the precipitated yeasts are larger and with little budding while the supernatants are isolated, smaller and with a significant budding, showing that these cells are in a proliferating process. As an example, in a centrifugation at 400 rpm Figure 7A shows the micrograph of the larger sized precipitated yeasts and Figure 7B, the micrograph of the smaller, significantly sprouting supernatant yeasts.

When flocculant and non-flocculant yeasts are mixed in equal proportions, when observed under the microscope, 15 they show a high precipitation of flocculant cells at slower speeds, see Figure 6C and 6E. These results show the potential of the serial centrifugation process to separate cells with superior fermentative potential (smaller and budding) and non-flocculant.

The present process allows yeast population segregation by age and cell activity.

The present process also allows flocculant cells to be cleaned from the process.

The population of yeasts coming from the additional centrifugations soon after the first centrifugation, due to its smaller size and weight, will be younger, presenting greater fermentative activity.

The yeast population from the first centrifugation is heavier because it is older or aggregated by the flocculation process and with less fermentative activity. The centrifugation process of the fermented broth with the centrifugal arrangement in series and prior to the distillation process allows the recovery of more yeasts compared to the current process, with direct benefits on the quality of the vinasse, which will have reduced levels of BOD because it contains too few yeasts and may even be absent in processes using higher centrifugations.

Current techniques do not allow this segregation of yeasts by acting on centrifugation at a single speed.

Current techniques allow a significant amount of

yeast is lost in the wine and its distillation in the vinasse, aggravating the harmfulness of vinasse on the environment.

Advantageously, the present invention allows the yeast milk to be returned to the fermentation process to be composed of a previously selected, younger, higher fermentative capacity population, translated into improved fermentative productivity rates.

In addition, in the case of flocculated yeasts that are present in some way in the fermentation process, the process of the present invention promotes the removal of these yeasts during low speed centrifugations, contributing to such yeasts not proliferating during the process, affecting the yield. fermentative. Indeed, as shown in Table 3, almost all flocculated cells would be eliminated in the first centrifugations.

Additionally the present process provides an increment

the possibility of bleeding / drying of yeasts, significantly increasing the possibilities of commercial use of surplus yeast generated during the fermentation process in relation to state of the art processes. The “bled” yeast (discarded) from the fermentation process will come primarily from the first centrifugation, that is, composed of the population of older yeasts with less fermentative and / or flocculated activity.

Claims (7)

1. Process for the separation and selection of yeasts for alcoholic fermentation from a yeast-aided sucrose load, said process comprising the steps of: a) after the first centrifugation (6), sorting and storing in tanks (11,12), the older and flocculated yeast for drying, obtaining a wine; (b) send the wine from step (a) via line (L13) to a lung tank (13); c) from the Tank (13) direct the wine via (L14) to the serial centrifugation process (14), with at least two centrifugations of increasing rotations of at least 400 rpm to 5000 rpm where the supernatant of each centrifugation becomes the next centrifugation charge and precipitate are collected, obtaining separate and selected young yeast and fermentation products; d) directing via (L15) said young and high fermentative capacity yeasts from step c) to the treatment tank (10) for dilution with conventional water and acid treatment; e) returning via (L19) said diluted and treated yeasts from step d) to the fermentation tanks (Fr); (f) by distilling off the fermentation products into wine (15), industrial alcohol (16) and vinasse (17) with an organic material content lower than that of vinasse resulting from state-of-the-art industrial ethanol production processes; use a single spin; and g) further drying yeast in the tank (13) and wrapping the yeast surplus from the various centrifuges. Process according to Claim 1, characterized in that in step c) the centrifugations take place between 400 and 4000 rpm. Process according to Claim 2, characterized in that in step c) centrifugation takes place at 1000 rpm. Process according to Claim 1, characterized in that the cellular concentration of yeast is maintained by the addition of yeasts from various centrifugations, provided that said addition is made with yeasts obtained from the higher speed centrifugation to that of. slower speed. Process according to Claim 1, characterized in that it separates flocculant cells from non-flocculant cells. Process according to Claim 1, characterized in that it reduces the proportion of undesirable flocculant cells relative to prior art analogous processes using a single centrifugation. Process according to Claim 1, characterized in that the excess of usable yeasts generated in the fermentation process is greater than that of prior art analogous processes using a single centrifugation.