Poly-b-hydroxybutyrate (PHB) is polymer from microbial origin are considered good substitute for plastics and isomers. Since in properties they are similar to petrochemical plastics, yet are truly biodegradable. The two potential bacteria Alcaligenes eutrophus and Rhizobium meliloti PHB production ability were analyzed using molasses as substrate at various concentrations in the fermentative medium (10%, 20%, 30% and 40%). Among this study maximum PHB was noted in high concentration of molasses (40%) in both bacteria, compared with Rhizobium meliloti and Alcaligenes eutrophus produce high amount of PHB in 40%. Alcaligenes eutrophus were optimized for two different carbon source (Sucrose and Maltose), nitrogen source (Ammonium chloride and Sodium nitrate) and various pH (5, 6, 7, 8 and 9). Among this maximum PHB was accumulated in maltose as carbon source, ammonium chloride as nitrogen source and 7 as pH. Thus the use of petroleum derived plastics can be minimized and by which we can live in a plastic pollution free earth.