C. fritschii TISTR 8527 was used hearafter as the strain for producing PHB. Under the normal growth condition (defined as cells grown in the normal media with complete nutrient, without acetate in the light). PHB level remained at the low level from 0.05% (w/cdw) to 0.65% (w/cdw) in all 72 day culture period (Figure 4.6) However, under the normal condition but with 0.4% (w/v) acetate supplement, PHB level continuously increased from 0.02% (day 0) to the maximum at 12.86% (day 48) and slightly reduced to 7.43% at day 72.