Self-flocculation, induce

Depending on the cell separation equipment used, the cell removal can be facilitated by inducing self-flocculation of cells (Stratford, 1989), or by adding flocculation polymers to the fermentation broth. Flocculants are added to create larger particles... 

Figure 7.5 Induced self-flocculation of oleoabundans grown in anaerobic digesters effluent (ABE)-based medium, (a) f. oleoabundans cells grown in ABE-based medium became self-flocculated, (b) oleoabundans cells grown in Bold s Basal Medium (BBM) were freely suspended (single cells).

Milk is a natural colloidal dispersion that contains casein micelles, self-assembled protein associates with a diameter of about 200 nm [20]. The casein micelles are protected against flocculation by an assembly of dense hairs (often called a brush ) at their surfaces. Polymer brushes can thus provide steric stabilization of colloids. For millennia, man used the fact that milk flocculates and gels when it is acidified, as in yogurt production. Below pH = 5 macroscopic flocculation of the casein micelles in milk is observed [21]. This means that the interactions between casein micelles change from repulsive to attractive. The explanation is that acidification leads to collapse of the casein brushes [22]. In cheese-making the steric stabilization is removed by enzymes, which induce gelation into cheese curd. 

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