Nicotiana tabacum cells are cultured to high density for production of polysaccharide gum. The reactor used is a stirred tank, containing initially 100 litres medium. The maximum specific growth rate of the culture is 0.18 d-1 and the yield of biomass from substrate is 0.5 g g-l. The concentration of growth-limiting substrate in the medium is 3% (w/v). The reactor is inoculated with 1.5 g l- 1 cells and operated in batch until the substrate is virtually exhausted; medium flow is then started at a rate of 4 l d-1. Fed-batch operation occurs under quasi-steady-state conditions. Fed-batch operation is carried out for 40 d. What is the final mass of cells in the reactor? _____________________ -triyambak.org