Figure 4. Growth and PHB accumulation from 48 hrs cultivation of R. sphaeroides N20 in GA medium with (a) (NH₄)₂SO₄; (b) NH₄NO₃; (c) and NH₄Cl at various concentrations (0-0.2 g/l) under aerobic-dark condition at 37ºC on a shaker (150 rpm). Cell harvested at 60 hrs.