DD290917A5 - PROCESS FOR THE PRODUCTION OF BIOGENIC EXTRACELLULAR FLOCKING AGENTS - Google Patents

Abstract

The invention relates to the production of a new bio-blocking agent by means of bacteria, wherein a new strain of Methylobacterium rhodesianum finds use. By culturing it under at least partial substitution of the conventional growth substrate methanol by chemical-thermal hydrolyzate of bacterial biomass, preferably activated sludge, bio-flocculating agents can be provided in a yield up to 0.4 g / g BTS in the neutral range. biopolymers; Cultivation; Bacteria; Methylobacterium rhodesianum; biomass hydrolyzate}

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 and in particular biomass, preferably for wastewater treatment, can be used.

Characterization of the known technical solutions

Various methods are known to obtain flocculants of microbial origin. Such flocculants are provided for various applications, such as water treatment, use for medical purposes, paper production, etc. The microorganisms, fungi and bacteria used have a wide spectrum in terms of their taxonomic affiliation, and the flocculant compounds themselves are either not further characterized in nature, or are given as proteins, polysaccharides or fatty acids. In most known cases, the production of bio-flocculants is subject to considerable problems. Thus, the Kultiviorungsprozeß is usually associated with low space-time yields, the required pure substrates for growth and product formation significantly burden the process economy, and for the product extraction complex work-up operations are required. Known methods come for a technical application of the flocculant, z. As in wastewater treatment, therefore not considered.

A method is known in which bacteria of the species Acetobacter methanolicus are cultivated and the release of flocculation-active biopolymers is induced by P-limitation. With this method, a part of the described disadvantages of the prior art can be circumvented. However, the product-forming bacteria require such a pH range during their cultivation, which is disadvantageous for a later use of the bio-flocculant in wastewater treatment, if you do not use purified product, but product-containing culture fluid directly. Furthermore, the use of methanol as a substrate for the cultivation of the claimed bacteria is required, which puts a heavy burden on the economy. An at least partial substitution of the substrate by enzymatically produced biomass hydrolysates, as described in US Pat. No. 4,041,182 for the cultivation of bacterial mixed populations, is not possible with these bacteria because they do not utilize any further C sources apart from glucose and methanol. Finally, the productivity of product formation for industrial use of the process is not sufficiently high.

Object of the invention

The invention aims to produce microbial flocculant using a cheap substrate with high yield.

Essence of the invention The invention is based on the object, such microorganisms for the production of extracellular bio-blocking agents

to provide and utilize, using biomass hydrolysates as a source of nutrients in the

Neutral area can be cultivated. According to the invention, this object is achieved by the new bacterial strain Methylobacterium rhodesianum IMET11401 under at least partial substitution of the growth substrate by chemical-thermal hydrolyzate of Bacterial biomass is cultivated. The new bacterial strain was included in the culture collection of the Central Institute of Microbiology and Experimental Therapy Jena deposited the AdW of the GDR. The culturing conditions are through a pH range of 6.5 to 7.3 and a Temperature range of 25 to 40 ⁰ C, preferably 32 ⁰ C, characterized. It has the following characteristics: cell morphology

gram-negative to gram-variable plump rods (0.8-1.2 x 1.5-4.0 mm), motile, nonspore-forming, cells often branched and pleomorphic, often containing inclusions of PHB

colony morphology

pink colonies: round, shiny, smooth-edged, convex, greasy consistency, diameter <0, max 1 mm (standard agar with methanol); Pepton agar: orange-red colonies

Physiological features Growth strictly aerobic lipase - Oxlase + lecithinase - Catalase + lysine carbene NOj reduction * + oxylase. - Urease ^ + ornithine Methyl red reaction - decarboxylase - Hj formation - arginine Indole formation - dihydrolase - Amylase - (+) Required Gelatinase - growth factor. - The biomass hydrolyzate can be obtained from the bacteria used as well as from others

municipal or industrial biomass, in so far as they contain no inhibitory substances that affect bacterial growth. Preferably, the use of activated sludge from municipal or industrial

Wastewater treatment plants suitable. The biomass hydrolyzate is made from the mentioned bacterial masses by treatment

obtained at pH> 8 in the temperature range of 80 to 17O ⁰ C. Preferably, a short-term heating at 120 ⁰ C and a pH of about 12 done. The hydrolysates contain lower amines, depending on the starting material.

Peptide fragments, mono- and oligosaccharides including amino sugars and a mixture of insoluble cell components. The latter can advantageously be separated before use of the hydrolyzate. The advantage of thermal-chemical

compared to the enzymatic hydrolysis is to be seen in the fact that the heavy metals contained in the biosludge among these

Reaction conditions are precipitated or absorbed on the solid and thus no longer after the separation of the solids

can have a toxic effect on the flocculant. Furthermore, the complete sterilization of the biosludge and the cheaper compared to enzymes and buffer substances use of basic technical chemicals is a significant advantage of the method according to the invention.

The bacterial hydrolyzate may partially or partially contain the conventional substrate methanol suitable for the bacterial strain

completely substitute, where appropriate, a balance of the C / N ratio will be required. Under otherwise optimal growth conditions, the distribution of the biopolymers takes place without the usually required limitation of a nutrient fraction. The extracellular biopolymers are water-soluble. They are partly in aggregated form with a

Knäueldurchmesser of> 0,4μπι ago. The content of amino groups on the carbohydrate molecule varies between 2 and 16%. With the method according to the invention can be using a cheap secondary substrate bio-blocking agent in Neutral area can be produced, which can be used preferably in wastewater treatment, the

accumulating culture medium can be used without further workup steps. The content of bioflocculants can be up to 0.4 g / g BM and is thus significantly higher than for previously known methods.

From the culture medium, the bio-blocking agent in a conventional manner, for. B. by precipitation with isopropanol, filtration

and drying.

The invention is explained in more detail by the following examples. embodiments Example 1:

Bacteria of Methylobacterium rhodesianum IMET11401 be fermented batchwise C and a pH of 6.2 to 6.8 at 32 ^0th The source of carbon and nitrogen is biosludge hydrolyzate and methanol. The Bioschlammhydrolysat is obtained by short-term heating at 150 ⁰ C and a pH of 12 from secondary excess sludge and then separating the solids. The hydrolyzate has a C: N ratio of about 4.6: 1. Since this ratio is insufficient for a growth of the microorganisms or a release of exopolysaccharides, must be compensated by the addition of methanol (1 part activated sludge hydrolyzate = 0.14 parts methanol-100 vol .-%). After a cultivation period of 72 hours, the flocculants separated from the microorganisms into the process water are separated off via a membrane cell by means of cross-flow microfiltration. The microorganism-containing suspension is circulated between the fermenter and the membrane cell. After the mass of the fermenter content has fallen by 33%, the removal of the flocculant is interrupted and replenished with a substrate mixture consisting of methanol and hydrolyzate.

The alternating processes of substrate feeding and flocculation removal can be repeated as often as desired. The flocculant is precipitated from the process water with the aid of iso-propanol, filtered off and dried. The concentrations of flocculants achieved were about 250 mg KH / l and 120 mg KH / g BTS.

Example 2: The bacterial culture IMET11401 is fermented continuously in the residence time range of 8 to 10 hours. The inorganic Nutrient solution has the following composition:

connection Required element in mg / g BTS KCI 10 H ₃ PO ₄ (80%) 20 MgSO ₄ × 7H ₂ O 2.5 CuSO ₄ X 5H ₂ O 0.2 FeSO ₄ × 7H ₂ O 0.337 ZnCl ₂ 0.154 MnSO ₄ 0.464 CoSO ₄ × 7 H ₂ O 0.0075

NiCl ₂ X 6H ₂ O 0.0228 CrCl ₃ X 6H ₂ O 0,015 Al ₂ (SO ₄ I ₃ 0,015 Ca (NO ₃ J ₂ χ 4H ₂ O .1499 H ₃ BO ₄ 0.225 Na ₂ MoO ₄ χ 2H ₂ O 0.0163

The C source was methanol. The rust P concentration is controlled so that they are alternately limited or in excess

is present. The fermentation suspension is pumped in the outer circuit via a membrane which communicates the aqueous medium with the

Flocculant passes and retains the biomass. The biomass is partly recycled and partly

separated.

The flocculant is recovered by precipitation, filtration and drying. The flocculant concentrations reached were 650 mg KH / I and 116.5 mg KH / gBTS, respectively.

Claims (2)

A process for producing biogenic flocculants by culturing bacteria using biomass hydrolyzate as a nutrient source, characterized in that the novel strain Methylobacterium rhodesianum IMET11401 is cultured with at least partial substitution of the growth substrate by chemical-thermal hydrolyzate of bacterial biomass. 2. The method according to 1, characterized by the use of a biomass hydrolyzate, which was obtained at pH> 8 and in the temperature range from 80 to 17O ⁰ C.