The present work was carried out to study incubation periods, scale up and biodisintegration of poly-β-hydroxybutyrate (PHB) synthesis by Stenotrophomonas maltophilia (WN2) and Pseudomonas putida (WN4) which were found to be the most efficient PHB producers. Poly-β-hydroxybutyrate (PHB) production by both WN2 and WN4 strains was investigated in mineral salt medium (MSM) supplemented with the optimum amount of carbon and nitrogen sources under the optimum pH value at different incubation times (between 12 h and 138h). Under optimized conditions, the tested strain; WN2 produced a PHB yield of 19.75 g/ L after 132h while WN4 produced 19.16 g/L after 120h. The tested strain WN4 performed better than the isolate WN2 according to their PHB productivity. Scale up studies were conducted in fermentors containing sterilized MSM broth containing glucose and ammonium sulphate (the best C and N sources) and maintaining the optimum C:N ratio (10:1). Samples were drawn to determine the PHB yields. Stenotrophomonas maltophilia produced a PHB yield of 1.954g /100ml culture which was marginally higher than 1.933g/100ml culture produced by Pseudomonas putida. The biodegradation of polyhydroxybutyrate (PHB) produced by the tested strains was done by using different soil types. The counts of PHB degrading microorganisms in natural environments were estimated. In infertile soil of Wady El-Natron and South El-Tahrir, ranged between 4.33x103/g dry soil and 1.6x104/g dry soil, respectively while, in fertile soil (Shalakan Farm), the number was 5.14x105/g dry soil.
Key words: Poly-β-hydroxybutyrate, Stenotrophomonas maltophilia, Pseudomonas putida, carbon and nitrogen sources, incubation time
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