JPH046345B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a flocculation treatment method for efficiently separating microbial cells during the process of culturing microorganisms to produce pharmaceuticals, agricultural chemicals, industrial chemicals, etc. BACKGROUND ART There are many fermentation industries that cultivate microorganisms for the purpose of utilizing the antibiotics, hormones, enzyme elements, etc. produced by microorganisms. The culture method used in the fermentation industry is generally carried out by suspending microorganisms in a culture solution containing various nutrients. After the culture is completed, heating and pH adjustment are performed, and then the microbial cells and the culture solution are separated using a decanter, precoat filter, etc. Problems with the conventional technology Since the microorganisms in the culture solution mentioned above have poor permanence, a large amount of diatomaceous earth is used as a super-assistant or pre-coating agent, but the microorganisms contaminated with these diatomaceous earths cannot be incinerated. I had no choice but to dump it. When bacterial cells are needed, a decanter is used, but the sedimentation of microbial cells is poor, the treatment capacity is low, and the moisture content of the bacterial cake is high. How to solve the problem Separation efficiency can be greatly increased by aggregating bacterial cells. However, adding inorganic flocculants such as iron salts and aluminum salts contaminates the liquid and bacterial cells. In biological treatment, which is a field of wastewater treatment, organic polymer flocculants are used to dehydrate sludge, which is a collection of microorganisms. However, the microorganisms in these sludges have the ability to self-flocculate and form aggregates, whereas the microorganisms in the culture solution do not aggregate but are dispersed. It also does not aggregate. As a result of various studies, the present inventor determined that the pH of the bacterial dispersion was
2.0 to 4.5, desirably 2.5 to 4.0, and add and mix polycarboxylate to give bacterial cells the ability to agglutinate, and add a cationic organic polymer flocculant to flocculate bacterial cells. succeeded in efficiently separating it from the liquid. As the polycarboxylate salt used in the present invention,
CMC, alginates, polyacrylates, polyacrylamide hydrolysates, polyacrylonitrile hydrolysates, polyacrylic acid ester hydrolysates, etc., and are water-soluble with monovalent cations such as sodium, potassium, and ammonium as counterions. polymers are used. The polycarboxylate salt can be added at any time before or after adjusting the pH, or can be added at the same time as adjusting the pH. The polycarboxylic acid salt used in the present invention is a polymer having an intrinsic viscosity of 1 dl/g or more, preferably 2 dl/g or more in 1N saline at pH 7.0, and is added and mixed in an amount of 0.1% to 2% per dry matter of the bacterial cells. . After adding and mixing the polycarboxylate, a cationic organic polymer flocculant is added to flocculate the bacterial cells. As the organic polymer flocculant used in the present invention, a copolymer of acrylic cationic monomer and acrylamide having a cation equivalent of 1.5 meq/g to 4.5 meq/g is effective, and preferably
Particularly effective are those with cation equivalents of 2 meq/g to 4 meq/g. The higher the molecular weight, the stronger the cohesive force, and those having an intrinsic viscosity of 5 dl/g or more in 1N saline are used. The acrylic cationic monomers used in the production of this cationic flocculant include dialkylaminoalkyl (meth)acrylamide, dialkylaminoalkyl (meth)acrylate, and those quaternized with alkyl halides, benzyl halides, dialkyl sulfates, etc. Examples include cationic monomers, and it is possible to copolymerize two or more of these monomers. The alkyl group in the cationic monomer is usually selected from lower alkyl groups such as methyl or ethyl. The cationic polymer flocculant used for this purpose is
It is of course possible to mix not only cationic polymer flocculants but also a small amount of anionic or nonionic polymer flocculant. Such a cationic polymer flocculant needs to be added in an amount of at least 0.2% or more, preferably 0.5% or more, based on the dry matter of the bacterial cells. Effects Carboxyl groups and amino groups coexist on the surface of microbial cells, which become negatively charged at a pH above the isoelectric point and positively charged below. The isoelectric point is a pH of about 4 to 5, and the bacterial cells are positively charged within the scope of the present invention. For this reason, it is thought that the polycarboxylic acid in the liquid has the ability to agglutinate by adsorbing to the surface of the bacterial cells, binding the bacterial cells to each other, and forming aggregates. Example 1 Aspergillus was cultured in a culture solution containing glucose, yeast extract, and nutrient salts, and a solution having a bacterial cell concentration of 1% was subjected to a test. After adding 200ml of the main culture solution to a glass beaker with a capacity of 500ml and adding the specified amount of polymer aqueous solution, add the tip with a diameter of 5mm.
Using a stirring rod with three round rods of 20 mm in length.
Stir for 20 seconds at 1000 rpm. Polycarboxylate is
Add the cationic polymer as a 0.1% aqueous solution, stir as described above, adjust the pH with hydrochloric acid, and then add the cationic polymer to 0.2%.
% aqueous solution and stirred again in the same manner to perform aggregation. The flocculated liquid was filtered by gravity through a 40-mesh nylon screen with an area of 38 cm ² , and then pressed at a pressure of 4 kg/cm ² for 30 seconds, and the moisture content of the resulting cake was measured. The amount of polycarboxylate and cationic polymer added was 100 ppm each to the culture solution, and the water content measurement conditions were 105°C for 15 hours. In the table below, "100ml
``Time required'' is the time required for 100 ml of the initial liquid to flow out under gravity. Test flocculant Γ polycarboxylate Sodium alginate [η] = 3.1 dl/g Γ Cationic polymer methacryloyloxyethyl trimethyl ammonium chloride/acrylamide copolymer [η] = 8.0 dl/g Cation equivalent value = 3.3 meq /g test results

[Table] Example 2 The same bacterial culture solution as in Example 1 was diluted with hydrochloric acid to pH 3.5.
It was adjusted to be suitable for testing. The same gravity overload test as in Example 1 was conducted using the same operations as in Example 1 except that the pH was adjusted in advance, and with the amount of flocculant added as shown in Table 2. Test results

[Table] Example 3 Streptomyces was cultured in a culture solution containing glucose, yeast extract, and nutrients, and the pH of the solution was adjusted to 3.0 with hydrochloric acid, and the solution was subjected to a test. A gravity overload test was conducted in the same manner as in Example 1 using the flocculant shown below. Test flocculant

【table】

【table】 Test results

【table】

[Table] Effects According to the present invention, microbial cells are easily aggregated, and the efficiency of separating the mother liquor and the cells is greatly improved. Therefore, a large amount of diatomaceous earth, which has been conventionally used as a super-aiding agent, is no longer necessary, and it is also possible to incinerate the bacterial cells. Since cleaning becomes easier, there are advantages such as improving the recovery rate of valuable materials.

Claims (1)

[Claims] 1. As a pretreatment for flocculating microbial cells in the fermentation liquid using a cationic polymer flocculant,
A method for coagulating and separating microbial cells, which requires two essential requirements: adjusting the pH to 2.0 to 4.5, and adding a polycarboxylic acid salt having an intrinsic viscosity of 1 dl/g or more in 1N saline. 2 The ion equivalent value of the cationic polymer flocculant is
1.5 to 4.5 meq/g and a limiting viscosity of 5 dl/g or more in 1 normal saline.