Present Technical Status Spray drying of the fermentation broth to which an anti-caking agent and a filling agent have been admixed, is used for preparation of salinomycin feed grade or the pure form is isolated after the biomass separation by extraction, concentration and purification of the raw product by recrystallization. Isolation of the pure form is rather demanding as concerns the high production costs and mechanical- technological equipment of the operation plant (US pat. Document 4,212,492, US pat. Document 4,137,247).

There is no need for pure form preparation should salinomycin be used as a veterinary drug or growth stimulator. After completion of the fermentation, the treated broth can be directly dried together with anti-caking agents admixed to it.

Before drying, the broth can be concentrated on an evaporator (US pat.

Document 4,395,491).

The harvested fermentation broth of salinomycin contains many by-products that pose a problem after spray drying of the broth. Solid substances agglomerate, form clods and can not be further processed. The major reason for the agglomerate formation is the content of fat. The fats contained in the solids manifest themselves predominantly in high temperature processing, when they are moist and at mechanical stress. The product obtained from the spray drier is very dusty, and therefore, it is necessary to granulate it (US pat.

Document 5,529,911).

The granulation process can be performed either directly in a combined fluid bed-spray drier, or at a subsequent isolation step using a dry or wet method of processing.

It has been found out that it is possible to isolate the solid substances in the form of granules. from the salinomycin fermentation broth without the formation of agglomerates.

Background of the Invention The above disadvantages are eliminated by the method for isolating salinomycin from the fermentation broth according to this invention. The nature of the invention consists in that the salinomycin fermentation broth is adjusted to an acidic pH value of 4 to 5. A suitable inert filtration aid such as diatomaceous earth, zeolites, wood flour or a mixture thereof is added in amount ranging from 5 to 20 wt % referred to the weight of the treated fermentation broth. The biomass is separated by filtration then granulated and dried in a fluid bed dryer.

Subsequently, the granules are ground and sieved to the required particle size.

The present method ensures a product which satisfies the veterinary code. It is advantageous that the active substance exists within an acidic pH range in cells of the biomass, and thus it is possible to discard the separated filtrate obtained by this process to the biological waste water treatment plant for aerobic treatment. Further, the dry matter content of the biomass thus obtained is higher than that of the fermentation broth, it being the reason that power consumption needed for drying the biomass is lower than the consumption for drying the whole amount of the fermentation broth.

Examples of Embodiments of the Invention Example 1 The fermentation broth obtained by fermentation of Streptomyces albus had, after 128 hours of cultivation, the pH value of 6,1 and a salinomycin content of 18,4 g/kg. 527 kg of the harvested fermentation broth have been adjusted by an addition of 10% HCI to a pH value of 4,0. Wood flour (8 wt % referred to the weight of the broth) was added to the treated fermentation broth. Using a rotary vacuum filter filled with wood flour we obtained 119,7 kg of biomass and 460,7 kg of filtrate which contained less than 0,01 % of salinomycin and after neutralisation it was discharged to the waste water aerobic treatment plant.

The separated biomass passed through a granulator and was dried in a fluid bed drier giving an amount of 74,2 kg of the product containing 12,3% of salinomycin.

Example 2 The fermentation by Streptomyces albus of the fermentation broth was terminated after 120 hours. The broth had a pH value of 6,0 and a salinomycin content of 22,6 g/kg. An amount of 589 kg of fermentation broth was adjusted by addition of 10% HCI to a pH value of 5,0. Zeolite and diatomaceous earth were added (15 wt % referred to the weight of treated fermentation broth). Using a rotary vacuum filter filled with diatomaceous earth, we obtained an amount of 184,7 kg of biomass and 495,6 kg of filtrate which contained less than 0,02% of salinomycin and was discarded as in Example 1.

The separated biomass was granulated and dried in the fluid bed drier giving an amount of 106,5 kg product containing 12,1% salinomycin.

Example 3 The fermentation broth obtained by fermentation of Streptomyces albus had, after 124 hours of fermentation, a pH value of 6,2 and a salinomycin content of 17,1 g/kg. By addition of a NaOH solution, a pH value of 7 to 8 was reached.

The fermentation broth thus treated was heated to a temperature of 60 °C, and after cooling, the pH value was adjusted by diluted HCI as in Example 1. Zeolite (20 wt % referred to the weight of the fermentation broth) was added to 524 kg of the treated fermentation broth. We filtered the mixture through a layer of diatomaceous earth filter aid using a rotary vacuum filter and obtained an amount of 184,7 kg of biomass and 495,6 kg of filtrate which contained less than 0,001% of salinomycin. The filtrate was discarded as in Example 1.

The separated biomass, having passed through a granulator, was dried in a fluid bed drier giving an amount of 80,7 kg of the product containing 10,9% of salinomycin.

Example 4 The fermentation broth obtained by fermenting Streptomyces albus had, after 128 hours of fermentation, a pH value of 6,3 and a salinomycin content of 15,5 g/kg. An amount of 566,6 kg of the fermentation broth was adjusted by an addition of 10% HCI to a pH value of 4,7. Diatomaceous earth (5 wt % referred to the weight of the fermentation broth) was added to the treated fermentation broth.

We used a rotary vacuum filter filled with diatomaceous earth. We obtained 100,7 of kg biomass and 500,6 kg of filtrate with a low content of salinomycin which, following neutralisation, was discarded to the waste water aerobic treatment plant. The separated biomass was then processed by granulation, dried in the fluid bed drier giving an amount of 68,4 kg of a dry product containing 12,8% of salinomycin.

Industrial Applicability Salinomycin is used in veterinary medicine as a coccidiostat coccidium and as a growth stimulator in feeding farm animals