Product formation in plug flow culture is type of continuous culture Back mixing is not found Substrate and cell mass concentration vary along the axis in the vessel

Flocculation Are usually used to form cell aggregate before centrifugation Flocculation is the agglomeration of small flocks into larger sattlable particles by using suitable flocculating agents.

Flocculating agents are usually polyelectrolyte or certain salts like CaCl2, MgCl2 etc. Polyelectrolytes used in flocculation- -are high molecular weight, water soluble organic compounds -can be either anionic, cationic or non-ionic in nature

Microbial pellet formation Shown by culture of filamentous/mycelial organisms such as molds and fungi Mycelial organisms which show apical growth Also grow exponentially. Filamentous fungi have a 'growth unit‘ is composed of the apex of the hypha and a short length of supporting hypha.

The total hyphal length of a mycelium and the number of tips increased exponentially at approximately the same rate. When the volume of the hyphal growth unit exceeds a critical volume a new branch, and hence, a new growing point, is initiated This is equivalent to the division of a single cell when the cell reaches a critical volume.

The rate of increase in hyphal mass, total length and number of tips is dictated by the specific growth rate : The rate of increase in hyphal mass dx/dt = μ X, The rate of increase in total length dH/dt = μ H, The rate of increase in number of tips dA/dt = μ A Where, x is biomass of hypha, H is total hyphal length and A is the number of growing tips.