Establishment of Suspension Cultures

A callus crumbles into smaller clumps and single cells in liquid medium by gentle agitation (100-120 rPM) on a shaker. Shaking the cultures also helps to aerate the P - cells. Such suspension cultures however rarely comprise single cells alone because cells tend to aggregate in clusters of 2-100. Suspension cultures can be maintained indefinitely by inoculations of known aliquot5 of cells to a fresh medium. This process is termed as "batch cultures". Alternatively, the medium is replenished at regular intervals. This process is termed as "continuous culture". In the continuous culture process at the time of replenishing the medium, cells are also harvested (open continuous system) or the biomass is allowed to increase (close continuous system).

Suspension cultures are useful in studying problems related to cell biology including cell cycle and production of secondary metabolites like alkaloids, steroids, glycosides, naphthoquinones, flavones etc. which find medicinal and industrial application. Pharmaceutical industries use large bioreactors for suspension cultures to obtain valuable bioorganic compounds. A bioreactor is a vessel of glass or steel in which cells are cultured aseptically and culture conditions are closely monitored. This results in higher yield of metabolites. In a bioreactor there is provision for adding fresh medium, for harvesting cells, for the aeration of products, for mixing and sampling, for controlling pH, O₂ content and temperature Plant cells are immobilised in alginate, agarose, polyacrylamide beads.