DD142719A5 - PROCESS FOR ENRICHING BIOMASS - Google Patents

Description

212

Process for the enrichment of biomass

Aerobic fermentation processes can be used industrially in an increasing extent to convert organic raw materials such as sugar and starch-containing media, η-paraffins, methanol and ethanol in quality biological products such as enzymes, metabolites or single cell proteins f_ see FIG. eg DE-OS .1.442.051, DE-OS 24 23 766, DE-OS 24 07 740, SU 498.940, JA 50-6 778_7-

These microbiological processes have in common that the fermentation product initially produces an aqueous suspension having a biomass content of up to 5% solids. The production of the biomass takes place in fumigated fermentation tanks in which the batch conditions or continuously favorable for the growth of microorganisms conditions such as temperature, pH, ionic strength, substrate concentration, oxygen partial pressure and turbulence can be adjusted.

, For working up the fermentation path and obtaining the desired products, a separation of the solids from the aqueous fermentation medium is often necessary as a first step. One uses settling or separators

such as filters, sewage sludge centrifuges, etc. These apparatuses only work properly if the solid to be separated has a sufficient density difference to the solution. · ·

For biological cell suspensions, however, this density difference is often very small. The sedimentation behavior is then mainly suspended by size and shape of the. Particles determined. In the separation of e.g. Bacteria with particle sizes of 1μ and smaller can reduce the amount of mechanical energy and capital costs associated with the separation of anaerobes by aggregating the individual particles, thus greatly increasing the particle size.

Various microorganisms spontaneously tend to flocculate, which thus becomes a racial feature. In other cases, after completion of the "fermentation and prior to the mechanical concentration by additional measures flocculation can be brought about, such as' by pH change, by addition of electrolytes / see J. VJeigl, Elektrokinetisch ^ interfacial processes, Verlag Chemie, Weinheim 1977, p. 88 et seq., F. Reiff et al., Eds., Die Hefen, volume I, Verlag Hans Carl, Nuremberg 19 60, S. 238_ /, by

-25 addition of polymers f_ cf. B. Alk in son u. JS Daoud in Adv. Biolog. Closely. Vol. III, Springer Verlag, 1974, p. 4 8__7 or water-soluble solvents. In addition, a temperature increase to 50 ° to 200 ⁰ C applied / ~ DE-OS 23 10 04 1_7. , ,

Apart from the only conditionally usable temperature method is all known flocculation processes as a prerequisite for sedimentation or separation, the addition of foreign substances in common, which are usually undesirable in the follow-up workup and therefore must be removed from further processing with great effort.

-j- 212 OO

In particular, methods are known in which by the action of an electric current die_. Removal of contaminants from aqueous solutions is effected. Thus, wastewater containing organic pollutants can be purified by oxidation with anodically formed oxygen at large-area electrodes. Here, the contaminants are chemically altered (FR-PS 2,316,196}.

In addition, various process variants are known in which formed by electrolysis fine gas bubbles after an optional preflocculence of the suspended particles by pH change, addition of polyvalent cations, mono- or polymeric flocculants connect with these particles and float them. In the electrolysis, however, a correspondingly high expenditure of energy is required to produce the gas bubbles / J 5,111,528-0; DE-OS 25 00 455; DE-OS 25 45 875; DE-OS 25 45 909; Food

Technology, Feb. 1974, p. 18 /. This will be in everyone

Trap causes a flotation, which leads to large-volume, poorly pressure-recoverable foams.

Furthermore, highly dilute particle suspensions can be clarified by passing them through an electric field of a DC voltage of 100-500 V and exciting the individual particles to migrate in this field. The method is effective only on aqueous solutions with very low solids contents (50 mg / l) (see, Pat. SU 573-713).

For wastewater treatment of food wastewater, flocculation and flotation due to gas evolution and cation formation by the influence of electric current on wastewater is known as electrocoagulation (see Food Technology, Feb. 1974, p. However, this process requires the same amount of time as a process control with chemical flocculants and thus represents no particular advantage.

The invention is therefore based on the object to provide a method which allows biomass in suspensions whose density is only slightly lower than that of the biomass without the addition of flocculants or other foreign substances, without the participation of gas bubbles and under Ve.r- message from thermal damage.

The object is achieved by a method for enrichment of biomass by coagulation of the solid. Fermentation suspension under the action of electric current, characterized in that the suspension at 20 to 100 ⁰ C of the effect of electric current

up to current densities of 10 mA / cm and a frequency of

0 to 2000Hz, preferably from 0 to 50 Hz exposes. 15

By specifying 0 to 2000Hz is to be expressed that DC and AC are equally suitable for performing the method.

, This process is in contrast to the already known process, the process that the coagulated individual particles regardless of an electrolytic evolution of gas at the electrodes, and especially in a current / voltage range at which this gas evolution does not occur, even when creating a corresponding set current to each other.

The process is generally carried out in such a way that the suspension in a suitable reaction. brings equipment, the desired temperature sets and then passes the desired current. The amount of electricity required for coagulation varies by species and type

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Concentration of the respective Fermentatiorissuspension dependent. It is possible the. Inventive enrichment to perform both continuously and discontinuously. A suitable reaction apparatus for the batchwise operation is, for example, a trough cell (see FIG. In this, the actual cell container (1) is provided with a tight-closing lid (2), through which the power supply to the electrodes • (3) and (4) are supplied and in which the openings

(5) for the feed of the suspension, (6) for the discharge of gases and (11) for a thermometer (9). The opening for the discharge of gases may be provided with a reflux condenser (not shown) in which vaporizing portions of the suspension may be condensed.

The trough cell is encased and can be connected through the inlet (7) and outlet (8) to a heating or cooling fluid circuit. The temperature of the suspension is monitored by a thermometer (9) or a thermocouple. The two electrodes (3 = anode) and. (4 = cathode) are arranged at a distance of 0.5 to 50 mm, preferably from 1 to 15 mm, to each other.

For example, nets or sheets of palladium or platinum and metal electrodes coated with metal electrodes, preferably titanium electrodes, mixed oxide-coated metal electrodes (als.anodes), preferably titanium anodes, or slotted and unslotted sheets of graphite are used as electrode material. The vertical arrangement of the electrodes can also be replaced by a horizontal one.

Likewise, the arrangement of a plurality of pairs of electrodes is possible, as has been proven especially in the block-like combination of angled or non-angled Kapillarspaltelektroden with and without vibration of the electrodes. During the passage of the current, the suspension can be mixed,

preferably by a stirrer, e.g. Magnetic stirrer (10), or by Urnpumpen, especially in the block-like combinations. If the process is operated continuously, then in the lid (2) of the electrolysis vessel (1) a further opening for continuous pumping of the suspension is provided.

From the circulated in the circulation suspension, a portion of the suspension is separated for further processing '' and each correspondingly fresh suspension was added.

Another, in particular, suitable for continuous procedure, the reaction apparatus is the flow cell. Particularly suitable are plate cells (see Figure 2). In a cell body of plastic or steel with rectangular cross-section (1) are in the simplest embodiment, two plate-shaped electrodes, the anode (3) and the cathode (4) at a distance of 1 to 60 mm. The suspension V7ird heated by the inlet (5) and removed at the outlet (12). In addition to the one-time passage of the suspension, it is also possible to repeatedly pass through it.

Another suitable flow cell is the tube cell (see Figure 3). In a cell body made of plastic or steel (1) are two concentric electrodes, the anode (3) and the cathode (4), which have a distance of 1 to 60 mm from each other. The suspension is fed at a suitable temperature through the inlet (5) and removed at the outlet (12). In this case, in addition to the single passage and multiple passage of the suspension is possible.

The process is usually carried out at atmospheric pressure. It can also be operated at elevated pressure;

By biomass is meant the mass of microorganisms contained in fermentation processes as a solid particulate matter in a fermentation solution,

Usually, microorganisms used are bacteria, yeasts and fungi. Examples of such microorganisms are methanol-utilizing bacteria of the genus Methylomonas e.g. Methylomonas clara ATCC 31,226, yeasts such as Candida lipolytica ATCC 20,383, which can be obtained by 'growing on n-Paraff.ine.n in the presence of an aqueous nutrient medium, or fungi, as they are commonly used in the known production of antibiotics, such as eg

 Penicillium chrysogenum.

The invention will be illustrated by the following examples, but without restricting them:

Example 1 :

Methylomonas clara ATCC 31266 was grown in a broth containing methanol as the carbon source, ammonia as a nitrogen source, phosphate, and iron, magnesium salts and other common trace minerals under aerobic conditions. 500 ml of a bacterial suspension thus produced having a solids content of 1.1% by weight were filled into a trough cell (see FIG. In this suspension dip two concentrically arranged platinum cylinders with 225 mesh / cm ² with 24 and 36 mm diameter and 95 mm in height. The outer electrode serves as an anode. The temperature is maintained at 35 ^° C. during the electrolysis. After switching on the direct current in experiment 1, the current is 0.1 A. This means an average current density, based on the anode area, of 0.93 mA / cm ² .

After 15 minutes, the power is turned off. The calculated mean cell voltage is 1.8 volts. The cell contents are then filled into a sedimentation vessel. -

The clear supernatant is decanted and the sediment is sent for further processing. In the same way as in experiment 1, experiment 2 to 5 is carried out. In experiments 3 to 5, however, instead of DC alternating current with frequencies of 20 Hz (experiment 3), 200 Hz

(Run 4) and 2000 Hz (Run 5). The ent-speaking current and voltage values are then information of; RMS value. Table 1 compares the results of the experiments with a blank test, '30. In experiments 3 to 5 the RMS values of the current and the voltage are given.

Table 1

Experiment No. Current / X7 Current density / ~: nA / cin ² _7 Voltage L vJ 'Sedime 3Ch' mtvolu after 60 / men 90 '- 1 0.1 0.93 1.8 not measurable 50 ml 50 ml 2 0.01 0.093 1.6 not measurable not understandable 45 ml ₃ a) 0.18 ^b) 1.67 ^b) 0.5 ^b > not measurable· 45 ml 45 ml 0.3b ⁾ - 2.79 ^b) 0.5 ^b) not measurable not measurable 40 ml ₅ d) 0.18 ^b) 1.67 ^b) 0.5 ^b > not measurable not possible 40 ml control 0 0 0 not measurable not measurable not measurable

a) Frequency 20 Hz b) RMS value c) Frequency 200 Hz d) Frequency 2000 Hz

It can be seen clearly the good to very good sedimentation of electrically treated samples compared to the untreated sample.

Example 2:

A hydrocarbon-utilizing strain of the yeast Candida lipolytica ATCC 20.383 was cultured on η-paraffins in the presence of an aqueous nutrient medium and an oxygen-containing gas. 500 ml of this suspension (solids content: 2% by weight) were filled into a trough cell (see FIG. 1) and treated as described in Example 1. The supernatant was decanted, the sediment was dried and weighed. The dry weight of the recovered biomass relative to the cell mass contained in the suspension is a measure of good flocculation.

Table 2 shows the proportions of the biomass obtained for 5 experiments as a function of current, voltage, current density and time.

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Table 2

Trial No. Stream C ^ J Current density ßkk / ov? J Tension nj Time /fi.n_7 Bi granny used .sse dnr.en c% j - 1 0.01 0.093 1.5 10 10.0 9.0 2 0.01 0.093 1.6 15 10.0. 9.4 3 0.05 0,465 1.7 15 10.0 9.6 4 0.1 0.93 1.8. 15 10.0 9.8 5 0.1 0.93 1.8 30 10.0 9.8 control I » - 0 - 10.0 5.0

One recognizes the significantly increased proportion of the obtained biomass of the electrically treated samples compared to the untreated sample,

Penicillium chrysogenum ATCC 10.238 was aerobically bred in a nutrient solution containing lactose, cornsteep liquid, phosphate, carbonate and magnesium sulfate by conventional methods. Using the electrodes described in Example 1, Experiment 1, DC is applied for a certain time and the filterability of the suspension is measured by measuring the filtrate volume / time.

Attempt ^ l:

500 mL of a mycelial suspension with 10 weight "~ - $ solids are electrolyzed for 15 minutes with 0,005 A at 20 ⁰ C. Afterwards: filter the suspension through a suction filter (pass through).

X

knife 11 cm, paper, vacuum 15 Torr) and measures the volume of the filtrate after 1 minute o

The results of experiments 1-5 of Example 3 are summarized in Table 3 and compared to a corresponding blank test.

table

Experiment No. Current / ~ A_7 current density tension Time / min7 Filtrate volcurrents / ml / min7 1 0.005 0.0465   1.4 15 VJL 2 0.01 0.093 1.5 15 30 3 0.05 0,465 1.6 15 85 4 0.1 0.93 1.7 15 90 VJl> 0.1 0.93 • 1 * 7 10   .90 control 0 0 0 3

One clearly recognizes the larger filtrate volume of the electrically treated samples compared to the untreated sample *

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Claims (3)

Four drive to enrich biomass PATENT CLAIMS '..' 1. A process for the enrichment of biomass by coagulation of the solid of a fermentation suspension under the action of electric current, characterized in that the suspension at 20 ° - 100 ⁰ C der-Viirkung an electric current up to stream densities of 10 mA / cm and a frequency from 0 to 2000 Hz, preferably 0 to 50 Hz, in particular O Hz (= direct current) exposes. 2. The method according to Anspruchi, characterized in that it is carried out batchwise - preferably under stirring or pumping the suspension - in a trough. , , _: 3. The method according to claim 1, characterized in that it is carried out continuously in a flow cell.