Wash time, centrifugal filtration

The coprecipitation technique is also very applicable to this type of separation. Here centrifugation or suction systems are often used to speed up the filtration and washing time. 

Even when size and size distribution per se impose no restrictions on the process, the filtration, washing, or centrifugation steps which usually follow crystallization may call for special crystal characteristics. Since fine crystals have a large specific surface area, excessive loss of product during washing may be encountered. Time and cost of filtration or centrifugation are highly dependent on crystal size distribution. 

The yeast produced by continuous culture techniques is separated from the liquid medium and solvent washed by centrifugation or filtration techniques. After drying, a protein supplement is obtained, which contains 65-68% protein and is suitable for addition to animal feeds. This protein content compares very favorably with that of dry fish meal, which contains about 65%, and dry skim milk powder with about 32%. The SCP processes have operated on the thousands of tonne/year scale in the U.K., France, and Italy, but regulatory problems with facilities operating on unpurified gas oil feedstocks have caused some shutdowns [64]. Nevertheless, because of a cell mass doubling time of 2.5-3 hr and the efficient carbon conversion to protein of this technology, these developments deserve to be explored further. 

TEGDA (Polysciences (Warrington, Pa., USA)) was purified by washing several times with an aqueous NaOH solution (10%) followed by washing twice with an aqueous solution of CaC. After centrifugation the extracted monomer was dried over anhydrous CaCl2 and filtrated. 

The insoluble material was removed by centrifuging at 5000 rpm for 15 min in a Beckman Model No J-6B centrifuge. This extraction with alkali was repeated twice more and the solutions of sodium salts of acids were collected. Humic acids were precipitated from the combined NaOH solutions by adjusting the pH to 1 with 2N HCl slowly with stirring and the mixture was left overnight. The precipitated humic acids were collected by filtration through Whatman IMM paper and washed with O.IN HCl. The filtrates were extracted three times with ethyl acetate and the extracts dried over sodium sulfate and evaporated, the residue constituting the fulvic acids. Buth fulvic and humic acids (precipitates) were air-dried, and then dried in a vacuum desiccator over phosphorus pentoxide at room temperature. 

Figure 4. The transport of by Chlorella under Os stress A. Control efflux from pre-loaded cells. A culture of 38°C-grown C. sorokiniana was preloaded with for 24 hrs. Cells were concentrated by centrifugation, washed, and resuspended as described in Figure 1, and assayed for Rfo loss by millipore filtration. The cells were dried, bleached, and counted by liquid scintillation as described by Fredrick and Heath (24). B. Influx into cells. A culture of exponentially growing C. sorokiniana was centrifuged, washed, resuspended in the Tris-Cl solution (see Figure 1) plus 100 fjM KCl, and placed in a 38°C water bath. At time intervals after RB addition, samples of cells were assayed as described in A.

The inorganic colloidal calcium phosphate associated with casein in normal milk dissolves on acidification of milk to pH 4.6 so that if sufficient time is allowed for solution, isoelectric casein is essentially free of calcium phosphate. In the laboratory, best results are obtained by acidifying skim milk to pH 4.6 at 2°C, holding for about 30 min and then warming to 30-35°C. The fine precipitate formed at 2°C allows time for the colloidal calcium phosphate to dissolve (Chapter 5). A moderately dilute acid (1 M) is preferred, since concentrated acid may cause localized coagulation. Acid production by a bacterial culture occurs slowly and allows time for colloidal calcium phosphate to dissolve. The casein is recovered by filtration or centrifugation and washed repeatedly with water to free the casein of lactose and salts. Thorough removal of lactose is essential since even traces of... 

The collection of bacterial cells from nutrient broths is typically done by batch centrifugation. This time-consuming operation can be replaced by membrane filtration. Filtration is faster than centrifugation, and it allows extensive cell washing. 

Resuspend the dried filtrates in 6 ml water and load 3 ml onto the columns by gravity flow and wash three times with 5 ml water. Centrifuge the columns (with plastic collection tube) for 5 min at 50 to remove all the water. Effluents can be discarded. 

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