Polyhydroxalcanoates (PHAs) have been recognized as a desirable alternative material to the non-biodegradable petrochemical produced polymers. The present study was focused on the isolation of the polyhydroxyalcanoates accumulating bacteria belonging to the genus Bacillus from different grass soil samples in Western Algeria and the optimization of several parameters such as cultural conditions and the nutritional requirements by the use of sugarcane and beet molasses as carbon source, implicated in the increase of polyhydroxyalcanoates production. Fifty-two Bacillus isolated strains were screened for intracellular lipids accumulation by staining with Sudan Black B. The obtained results showed that 8 isolates of the genus Bacillus were positively stained. Based on the morphological and physiological properties and sequence of its 16S rDNA, the selected most accumulating polyhydroxyalcanoates strain L9 indicated was identified as Bacillus megaterium. Furthermore, Bacillus megaterium was explored for a potential to synthesize polyhydroxyalcanoates by the using of different Carbon and nitrogen sources. The presence of biopolymer granule in cells of Bacillus megaterium strain L9 indicated that the accumulation was depended on the ratio of carbon and nitrogen sources in the used culture medium. The highest polyhydroxyalcanoates accumulation (0.25 g.L-1) was obtained by the using glucose and NH4Cl. Furthermore, regarding the utilization of beet molasses as sole carbon source in the culture medium at concentration of 3%, has induced considerably the polyhydroxyalcanoates yield accumulation after 48h of growth (41% w/w), whereas the highest biomass (0,6 g.L-1) was obtained at concentration of 4% beet molasses supplemented with 0,05% ammonium chloride. The present study indicated the benefits of conversion of available agro-industrial wastes materials into a valuable product.
