Screening, identification and production of polyhydroxyalkanoates (PHAs)by sucrose utilizing microbes isolated from soil environments
Polyhydroxyalkanoates (PHAs) and their derivatives are polyester and can be used as a substitute for synthesized plastic. Increasing the industrial interest of biopolymer of PHAs, sucrose utilizing microbes from soil collected from sugarcane plantation were screened for evaluation of their ability to accumulate PHAs. Among 72 isolates were picked and transferred to mineral salt medium (MSM) containing sucrose as a sole carbon source, 33 strains can be grown on sucrose agar medium and were further studied to observe PHAs accumulation in their cells using microscopic technique. The results revealed that 3 isolates had positive for PHAs producing strains. Only one strain presented a strong Sudan Black and Nile blue A staining and was identified by 16S rDNA nucleotide sequence homology. From its morphology and physical properties, the isolated strain showed closely related to Hydrogenophaga pseudoflava (99% identify). To consider PHAs production by the isolated strain, grown on media containing 20 gL -1 sucrose and 1 gL -1 ammonium sulphate at pH 7 under controlled temperature of 35°C. Maximum dry cell weight (DCW) and maximum PHAs production were obtained at 3.61 gL -1 and 2.41 gL -1 after 36 and 42 hours of batch fermentation. The sucrose uptake in culture medium measured by total organic carbon (TOC) analyzer was 14.73 g within 48 hours. The highest PHAs inclusions in microbial cell was 68.15 % (g PHAs/g DCW) giving maximum PHAs yield (YP/S) of 0.17 (g PHAs/g Sucrose) and a productivity of 0.057 g PHAsL -1 h -1 . The extracted PHAs were compared with the analytic PHAs and were confirmed to be PHAs by several standard techniques. This study highlights the potential of the bacterial diversity in the soil environment and this characteristic may be an exploitable application for the industrial production of PHAs.