SURVEYING THE IN VITRO EFFECT OF DIFFERENT CARBON AND NITROGEN SOURCES ON POLY-β-HYDROXYBUTYRATE (PHB) BIOPLASTIC SYNTHESIS CAPACITY OF Rhizobium gallicum M40.1

Abstract

The aim of this study was to survey the in vitro effect of different organic carbon and nitrogen sources on the PHB bio-plastic production synthesized by Rhizobium gallicum type M40.1 in liquid yeast extract manitol medium (YEMM). Manitol, sucrose, molasses and starch were used as tested organic carbon sources. Addionally, NH₄Cl, (NH₄)₂SO₄, glycine, yeast extract and TPY (included trypton, yeast extract and peptone with the ratio of 1:1:1) were considered as nitrogen sources. Rhizobium gallicum type M40.1 with a function of PHB bio-plastic synthesis was isolated from soil and the experiments were conducted under in vitro laboratory conditions. The results showed that the amount of synthesized PHB bio-plastic by Rhizobium gallicum type M40.1 in the treatment supplemented with sucrose as an organic carbon source was significantly higher than that in the others, with an amount of 0.127 g/L which obtained 41.06% PHB synthesized under continuous condition after 60 hours of incubation. The different results in nitrogen sources illiminated the NH₄+ supplementation from NH₄Cl, (NH₄)₂SO₄, glycine and the mixture of trypton: peptone: yeast extract (TPY) with NH₄Cl contributed better PHB systhesis capacity with 0,029 ± 0,013 g/L equal to 61,09%. The result of the effect of different nitrogen source supplement on PHB bio-plastic synthesizing capacity of Rhizobium gallicum type M40.1 in YEMM revealed that the larger amounts of synthesized PHB bio-plastic were found to be 3 times higher in all NH₄Cl  containing nitrogen source treatments with concentration of 1% than that of the yeast extract powder treatment with the same concentration under discontinuous fermentation conditions.

Keywords: Bioplastic, nitrogen sources, organic carbon sources, PHB, Rhizobium gallicum M40.1.