METHOD FOR PRODUCING A BIOMASS WHICH CAN BE EASILY BROKEN DOWN AND WHICH HAS AN INCREASED CONTENT OF POLYUNSATURATED FATTY ACIDS

Abstract

According to the invention, it has been found that when the amount of sulfate used in the culturing of PUFAs-producing cells is selected such that the sulfate concentration drops to zero in the last phase of the growth phase of the cells, an easily disruptable biomass is obtained which has an increased proportion by mass of polyunsaturated fatty acids (PUFAs) in the final product.

Claims

1-15. (canceled)

16. A process for producing a biomass containing PUFAs, comprising culturing PUFAs-producing cells in a fermentation medium, wherein the sulfate content in the fermentation medium is adjusted such that the sulfate concentration falls to zero in the course of fermentation.

17. The process for producing a biomass containing PUFAs of claim 16, wherein the process comprises a growth phase and an oil-production phase, and wherein the sulfate concentration in the fermentation medium falls to zero before the start of the oil-production phase.

18. The process of claim 17, wherein the sulfate concentration in the fermentation medium falls to zero in the second half of the growth phase.

19. The process of claim 16, wherein the amount of sulfate is such that there is a final sulfate concentration of 7 to 10 g of sulfate per kg of biomass.

20. The process of claim 16, comprising as a further step, a mechanical disruption of the biomass obtained using a mechanical force of up to 12 Wh/g.

21. The process of claim 16, comprising, as a further step, a mechanical disruption of the biomass obtained using a mechanical force of 1 to 10 Wh/kg.

22. The process of claim 16, wherein oil is isolated from the fermentation medium obtained.

23. The process of claim 16, wherein the fermentation broth thus obtained is, optionally after prior concentration, further processed to give a feedstuff.

24. The process of claim 16, wherein the cells are cultured to a biomass density of at least 50 g per litre of fermentation medium.

25. The process of claim 24, wherein the sulfate concentration in the medium falls to zero after a biomass density of at least 50 g per litre of fermentation medium has been reached.

26. The process of claim 16, wherein the cells are cultured in the growth phase to a biomass density of at least 100 g per litre of fermentation medium.

27. The process of claim 26, wherein the sulfate concentration in the medium falls to zero after a biomass density of at least 100 g per litre of fermentation medium has been reached.

28. The process of claim 27, comprising, as a further step, the mechanical disruption of the biomass obtained using a mechanical force of up to 12 Wh/g.

29. The process of claim 16, wherein the oil-production phase is introduced by limiting at least one limiting nutrient component.

30. The process of claim 29, wherein the limiting nutrient component is nitrogen.

31. The process of claim 16, wherein the sulfate concentration in the medium is below

0. 05 g per kg of fermentation medium during the entire period of the oil-production phase.

32. The process of claim 16, wherein the fermentation medium contains a chloride content of not more than 3 g per kg during the entire fermentation.

33. The process of claim 16, wherein the cells are of the family Thraustochytriaceae.

34. Biomass comprising PUFAs, microorganisms of the taxon Labyrinthulomycetes, and 7 to 10 g of sulfate per kg of biomass.

35. The biomass containing PUFAs of claim 34, wherein the cells are of the family Thraustochytriaceae.

Description

Exemplary Embodiments

EXAMPLE 1

Producing Biomass by Fermentation of Aurantiochytrium Limacinum SR21 in a Medium having a High Sulfate Content and Subsequent Drying of the Biomass

[0158] The cells were cultured for about 70 h in a feed process using a steel fermenter having a fermenter volume of 2 litres with a total starting mass of about 700 g and an attained total final mass of about 1.5 kg. During the process, a glucose solution (570 g/kg glucose) was metered in (“fed-batch process”).

[0159] The composition of the starting medium was as follows:

[0160] Medium 1: 20 g/kg glucose; 4 g/kg yeast extract; 2 g/kg ammonium sulfate; 12 or 16 g/kg sodium sulfate; 2.46 g/kg magnesium sulfate (heptahydrate); 0.45 g/kg potassium chloride; 4.5 g/kg potassium dihydrogen phosphate; 0.1 g/kg thiamine (HCl); 5 g/kg trace element solution.

[0161] The composition of the trace element solution was as follows: 35 g/kg hydrochloric acid (37%); 1.86 g/kg manganese chloride (tetrahydrate); 1.82 g/kg zinc sulfate (heptahydrate); 0.818 g/kg sodium EDTA; 0.29 g/kg boric acid; 0.24 g/kg sodium molybdate (dihydrate); 4.58 g/kg calcium chloride (dihydrate); 17.33 g/kg iron sulfate (heptahydrate); 0.15 g/kg copper chloride (dihydrate). Culturing was carried out under the following conditions: Culture temperature 28° C.; aeration rate 0.5 wm, stirrer speed 600-1950 rpm, control of pH in the growth phase at 4.5 using ammonia water (25% v/v). Fermentation was carried out up to a biomass density of 80 g/l before the oil-production phase was introduced by limitation of phosphate and nitrogen. Because of the high sulfate content in the starting medium until the end of fermentation, i.e. including until the end of the oil-production phase, the sulfate concentration is always above the saturation limit of the cells, which is about 5 g per kg of dry biomass. The biomasses obtained are hereinafter referred to as “Biomass 1” (12 g/kg sodium sulfate in the starting medium) and “Biomass 2” (16 g/kg sodium sulfate in the starting medium).

[0162] The sulfate content of the biomass obtained was determined by determining the sulfur content of the biomass in accordance with DIN ISO 11885.

Example 2

Producing Biomass by Fermentation of Aurantiochytrium Limacinum SR21 in a Medium having a Low Sulfate Content and Subsequent Drying of the Biomass

[0163] The cells were cultured for about 70 h in a feed process using a steel fermenter having a fermenter volume of 2 litres with a total starting mass of 712 g and an attained total final mass of about 1.5 kg. During the process, a glucose solution (570 g/kg glucose) was metered in (“fed-batch process”).

[0164] The composition of the starting medium was as follows:

[0165] Medium 1: 20 g/kg glucose; 4 g/kg yeast extract; 0 g/kg ammonium sulfate; 2.46 g/kg magnesium sulfate (heptahydrate); 0.45 g/kg potassium chloride; 4.5 g/kg potassium dihydrogen phosphate; 0.1 g/kg thiamine (HCl); 5 g/kg trace element solution.

[0166] The composition of the trace element solution was as follows: 35 g/kg hydrochloric acid (37%); 1.86 g/kg manganese chloride (tetrahydrate); 1.82 g/kg zinc sulfate (heptahydrate); 0.818 g/kg sodium EDTA; 0.29 g/kg boric acid; 0.24 g/kg sodium molybdate (dihydrate); 4.58 g/kg calcium chloride (dihydrate); 17.33 g/kg iron sulfate (heptahydrate); 0.15 g/kg copper chloride (dihydrate). Culturing was carried out under the following conditions: Culture temperature 28° C.; aeration rate 0.5 wm, stirrer speed 600-1950 rpm, control of pH in the growth phase at 4.5 using ammonia water (25% v/v). Fermentation was carried out up to a biomass density of 80 g/l before the oil-production phase was introduced by limitation of phosphate and nitrogen. The sulfate concentration had already fallen below the detection limit of 0.05 g per kg of fermentation medium upon introduction of the oil-production phase, and the sulfate concentration was accordingly also below the detection limit during the entire oil-production phase. And since there was no metered addition of sulfate, the sulfate concentration fell to zero in the course of the oil-production phase. The biomass obtained is hereinafter referred to as “Biomass 3”.

EXAMPLE 3

Work-Up and Comparison of the Biomasses Obtained and of the Processes

[0167] After the culturing process, the fermentation broths were heated to 60° C. for 20 minutes in order to prevent further cellular activity.

[0168] This was followed by a two-stage drying of the biomass: Firstly, the fermentation broth was concentrated by evaporation to a dry mass of about 20% by weight. Thereafter, the concentrated fermentation broth was spray-dried using a Production MinorTM Spray Dryer (GEA NIRO) at an inlet temperature of the drying air of 340° C. Spray-drying thus gave a powder with more than 95% by weight of dry mass.

TABLE-US-00001 TABLE 1 Comparison of the biomasses obtained Sulfate content Yield [%] Product, Purity [%] Bio- [g/kg] (sulfate (g DHA per g total [g] (g DHA per g mass per kg biomass) dextrose) (g DHA) dry biomass) 1 29.7 7.8 44.2 15.7 2 32.5 7.3 45.4 15.4 3 8.4 7.1 35.5 20.1

[0169] Biomasses 1 and 2 are biomasses obtained by fermentation at high sulfate content as per Example 1; by contrast, Biomass 3 is a biomass obtained by fermentation at low sulfate content as per Example 2.

[0170] It can be discerned that the fermentation process which was carried out at low sulfate content and led to Biomass 3 delivered a product having distinctly higher purity, i.e. a product having a distinctly increased proportion of DHA, than those processes which were carried out at high sulfate content and led to Biomasses 1 and 2. In addition, the sulfate content in the biomass obtained is also distinctly lower than in the case of the process with high sulfate content.