Separation of cells and proteins from fermentation broth in a shear-enhanced cross-flow ultrafiltration module as the first step in the refinement of lactic acid |
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Authors: | Anna Toräng Ann-Sofi Jönsson Guido Zacchi |
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Institution: | (1) Department of Chemical Engineering 1, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden |
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Abstract: | A shear-enhanced, cross-flow ultrafiltration module was used to separate cells and proteins from the fermentation broth. Three
(fermented) media were studied: rich medium, rich medium with hydrolytic enzymes added after fermentation, and wheat flour
hydrolysate. To find a membrane with as high a flux as possible, but still capable of separating cells and proteins from the
lactic acid containing broth, the performance of three hydrophilic membranes of varying cutoffs (10,000, 20,000, and 30,000)
and one hydrophobic membrane (cutoff 25,000) was investigated. The proteins produced by the lactic acid bacteria during fermentation
and the hydrolytic proteins were retained by the hydrophilic membrane with a cutoff of 20,000, whereas wheat flour proteins
were detected in the permeate. In the permeates from the hydrophobic membrane (cutoff 25,000), almost no proteins were detected.
The flux of the whole-wheat flour hydrolysate was significantly lower than that of rich medium, for both the hydrophilic and
the hydrophobic membranes. The flux was, in all cases, higher for the hydrophilic membrane (12–85 L/m2·h], depending, on which medium was treated) than for the hydrophobic one (8–45 L/m2·h]), even though the nominal cutoffs of the hydrophobic and hydrophilic membranes were almost the same. However, the difference
in flux was smaller when the whole-wheat flour hydrolysate was processed (12 vs 8 L/m2·h]) than when the rich medium was processed (85 vs 45 L/m2·h]). Protein retention was higher for the hydrophobic membrane than for the hydrophilic membrane (cutoff 20,000) owing to
blocking of the pores by proteins adsorbed on to the hydrophobic membrane surface. |
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Keywords: | Lacticacid membrane separation ultrafiltration wheat flour |
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