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Studies of the formation, separation and dewatering of aggregated biological materials.

Bentham, Alan Craig; (1990) Studies of the formation, separation and dewatering of aggregated biological materials. Doctoral thesis (Ph.D.), University College London. Green open access

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Abstract

The formation of aggregates of biological materials and their subsequent separation are key steps in the biological industry. Two systems involving the formation and dewatering of biological aggregates have been studied. In the first, study soya protein was precipitated and then ultrafiltered in hollow-fibre membranes. It was shown that high protein concentrations could be obtained by appropriate choice of membrane geometry and pumping equipment. Rheological measurements of the suspension were used to explain the permeate flux rates at high protein concentration. The feasibilty of using microfiltration for precipitate dewatering was assessed by studying the flux and protein transmission characteristics of flat-sheet microporous membranes. The second study examined the suitability of a scroll decanter centrifuge for the removal of yeast cell debris from yeast homogenate. The cells were disrupted by high-pressure homogenisation and borax was used to aggregate the cell wall material by selectively cross linking carbohydrates having cis-1,2 diol groups. The effects of adjusting centrifuge parameters on the clarification of the homogenate, protein recovery and sediment dewatering were examined. The dewatering of homogenate solids was related to the shear modulus of the sediment. Further clarification of the yeast homogenate suspension was achieved by centrifugation after flocculation of sub-micron cell debris using polyethylene imine (molecular weights 600-70,000). Maximum clarification of the suspension was found to occur at a polymer dose corresponding to zero electrophoretic mobility in the homogenate and it was seen that higher doses of polymers of higher molecular weight recharged and restabilised the homogenate suspension. It was found that the interaction of the polymer with the suspended solids and the soluble components (lipids, proteins and nucleic acids) of the homogenate was dependent on the pH and ionic concentration. Separation of the flocculated material was achieved on a pilot plant scale using a disc-stack centrifuge.

Type: Thesis (Doctoral)
Qualification: Ph.D.
Title: Studies of the formation, separation and dewatering of aggregated biological materials.
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by Proquest
URI: https://discovery.ucl.ac.uk/id/eprint/10109319
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