DD285991A5 - PROCESS FOR THE PRODUCTION OF BIOGENIC EXTRACELLULAR FLOCKING AGENTS - Google Patents

Abstract

The invention relates to a process for the production of biogenic extracellular flocculants. The microbial production process for a novel flocculant uses the known bacterial species Acetobacter methanolicus as a producer of flocculatively active biopolymers, wherein the induction of the Ausschuettung is effected by a P-Limitation. In this case, the cultivation process is driven to the critical flow rate and the P dosage is carried out discontinuously so that an oscillation within the limitation range is achieved. The recovered flocculant is effective against its producers as well as other microorganisms and other suspended particles. biopolymer; Induction; limitation; Production method; Bacteria; Acetobacter methanolicus; Durchfluszrate}

Description

Field of application of the invention

The invention relates to the preparation of a bio-blocking agent, which z. B. for the concentration of sediment, for water treatment, the paper industry and in the medical field can be used.

Characteristic of the known state of the art

The literature has described a number of processes dealing with the production of flocculants of microbial origin. Such flocculants are provided for various applications, such as water treatment, use for medical purposes, paper production u. The microorganisms, fungi and bacteria used have a wide range in their taxonomic affiliation, and the flocculant compounds themselves are either not further characterized in nature, or are given as proteins, polysaccharides or even fatty acids.

U.S. Patent 4,258,132 claims the preparation of an agglutinating substance from Dermatiacea. The cultivation of the microorganisms is a residence time of 72 hours, moreover, gelation occurs during the fermentation, which adversely affects the microbial growth and process control. In addition, a multi-stage workup is required.

In U.S. Patent 4,514,560, an aggregate-end polysaccharide synthesized by Aureobacidium is described. Also in this proposed method, the final product is obtained by a time and chemical consuming work-up; the cultivation process is also associated with only a small space-time yield.

This feature is inherent in all processes which are known in the prior art for the problem of generating aggregation-promoting biopolymers: even in batch mode, the process can only be realized with long reaction tents in the fermentor and thus always exhibits a poor space-time yield ,

When the polymers are intracellular compounds, a recovery process involves lysing of the producers. Thus, according to EP 149514, a flocculant is obtained which is prepared by thermal or chemical lysis of various cultures (Pseudomonas fluorescens, P. putida, Bacillus cereus or E. coli). The cultivation times are up to 270 hours. Thus, only a small space-time yield is recorded here, the lysis itself requires appropriate measures that burden the economy of the process.

US Pat. No. 4,649,110 also discloses a process in which the phylum Cocobacteria strain Phoranidum sp. cultured and both the lysis ingredients as well as excreted polymers can be used as a flocculating active component. It requires special guidance of the Ca ion concentration, which is high during the exponential growth of the bacteria and is reduced to induce the release of the polymers. Also in this method, the microbial extraction of the flocculant several days culture time are given, so that a low space-time yield results. For the realization of an industrial flocculation process, the recovery processes known in the art are not suitable.

Object of the invention The object of the invention is to inexpensively produce a mibobial flocculant under high space-time yield. Essence of the invention

The invention has for its object to select powerful microorganisms and indicate the required process conditions under which flocculant compounds are released into the culture medium. According to the invention, this is done by culturing bacteria of the species Acetobacter methanolicus in a continuous process near the critical flow rate, whereby the induction of the distribution of flocculation-active biopolymers by P-Limitation.

The suitability of bacteria of the species Acetohacter methanolicus as a producer of extracellularly active biopolymers is

completely surprising.

It is known that stems of this type have only a minimal number of electronegative charge carriers, resulting in Failure of all known flocculants leads, the mode of action based on bridge bonding effects. Suspensions, the Contained bacteria of Acetobacter methanolicus, have a high coagulation stability. Destabilization and thus So far, sedimentation of the bacteria could only be achieved if a thermal and / or alkali treatment was successful. Coagulation with lectins was also unsuccessful. Even the attempt of a heterologous aggregation of the strains of A. methanolicus by E. coli bacteria led to success only in isolated cases, but without technically exploitable Efficiency. The Faqhmann had no evidence from his many years of research that these tribes

as producers of a microbial flocculant could be successfully viewed.

It has now surprisingly been found that in contrast to this view strains of the type mentioned then

Flocculant biopolymers in the medium of an ongoing under optimal biomass growth continuous

Spill out cultivation process when P-Limitation such a release is induced and the Cultivation process is driven near the critical flow rate. The advantageous parameter range for this is 0.11 to

0.13 / h, preferably 0.125 / h.

The P limitation required for inducing the biopolymer output is determined by a phosphate concentration of

<16mg POa-P / I reached. According to the invention, the dosage of the P source can advantageously be discontinuous, in order to maintain a finite, non-inhibitory substrate concentration in the case of P limitation. In this case, a distribution of flockülierend acting polymers is achieved, the process of biomass formation itself, however, not adversely affected. Because the

P-Limitation needs to be effective only for a short time, can at almost maximum growth rate of Microorganisms high productivity of biomass formation can be maintained by a high proportion of active biomass. It has proved to be particularly advantageous if, using phosphoric acid as the P source, the regulation of the

pH value and by a discontinuous dosage an oscillation of the phosphate concentration in one

Concentration range of 0 to 60 mg PO4-P / I is achieved. In this case, the Llmitationsbereich <16 mg PO4-P / I and go through

triggered the Biopolymerausschüttiing. When reaching the lower limit concentration, phosphoric acid must be dosed immediately. The oscillation times should be in the order of magnitude of the residence time.

The flocculant may be prepared in a known manner by precipitation with quaternary ammonium compounds, through Membrane separation process or be concentrated by thickening in vacuo. For special applications, eg. As in wastewater treatment, a concentration of the flocculant is not necessarily

required because the concentration in the culture fluid allows direct use.

The most surprising and technically significant effect of its use is the ability to produce strains of A. methanolicus to flake and thereby cause self-sedimentation. This is a significant improvement of their Concentrability connected. In addition, it is against many other microorganisms and particulate solids

effective.

The invention will be explained in more detail by the following examples. Ausführungsbelsplele example 1

Bacteria of the strain Acetobacter methanolicus IMET B346 are continuously cultured aerobically at pH 4.1 and at 32 ⁰ C mi 'diner flow rate of 0.11 h "' The nutrient solution has the following composition (supplies element per g biomass).:

element mg / g BTS connection K 10 KCI P 20 H3P0 " mg 2,500 MgSO ₄ -7H ₂ O Cu 0,200 CuSO ₄ -5H ₂ O Fe 0.337 FeSO ₄ -7 H ₁ O Zn 0.154 ZnCl ₂ Mn 0.464 MnSO ₄ Co 0.0075 CoSO ₄ -7H ₂ O Ni 0.0228 NiCl ₂ 6 H ₂ O Cr 0.0150 CrCl, -6H ₂ O al 0.0150 AI ₂ (SO ₄ ), Ca .1499 Ca (NO ₃ ), - 4H ₂ O B .2250 H ₃ BO ₄ Mo 0.0163 Na ₂ MoO ₄ -2H ₂

As C source, a 15% by volume methanol solution (residual methanol concentration in the fermenter 0.1 g / l) is added as C source. To trigger the flocculant release, the current phosphate concentration of 100 mg / l (based on 5 g / l BTS) is reduced to 16 mg / g. The amount of polysaccharide excreted extracellularly under these conditions is 96 mg / g BTS. The effectiveness of the bio-blocking agent is determined turbidimetrically to kaolin and is of the same order of magnitude as for the synthetic flocculant poly-DMDAAC.

Example 2

In a continuous fermentation bacteria of the strain Acetobacter methanolicus IMET11402 are cultivated at a flow rate of D - 0.126 h ' ¹ , a pH of 4.1 and at 32 ⁰ C. Nutrient solution and methanol as C-containing substrate are used as indicated in Example 1. The P concentration of the nutrient solution is controlled by discontinuous metering of the phosphoric acid so that the phosphate concentration oscillates in the range of 0 to 50 mg / l. When the lower limit is reached, phosphoric acid is immediately metered. The oscillation time is 8 hours. Under these conditions, 140 mg exocellulres biopolymer per g of BTS is obtained. It corresponded in its effectiveness flocculant according to Example 1.

Claims (4)

1. A process for the production of biogenic extracellular flocculants by culturing bacteria, characterized by - Cultivation of bacteriaArtAcetobactermethanolicus in one - continuous process near the critical flow rate as well - Inducing the distribution of flocculation-active biopolymers by P-limitation 2. The method according to claim!, Characterized by a flow rate of 0.11 to 0.13, preferably from 0.125 / h. 3. The method according to claim 1, characterized by a P concentration in the range of 0 to 50 mg PO ₄ -P /!, Preferably of <16mg / l. 4. The method according to claim 1 and 3, characterized by a discontinuous dosage of the P source oscillating adjustment of the P-Limitation, wherein the oscillation times should be in the order of the residence time.