Statistical optimization for polyhydroxybutyrate production by locally isolated Bacillus safensis using sugarcane molasses under nutritional stressed conditions

Abstract

Background and objective Biodegradable polymers, such as polyhydroxyalkanoate (PHAs), have recently been recognized as polyesters owing to their properties as biodegradable thermoplastics. Materials and methods The main objective of this study was to isolate an efficient polyhydroxybutyrate (PHB) producer from soil collected from different rhizospheric areas in Egypt. The potent strain was identified using 16 s rRNA sequence analysis. Plackett–Burman and central composite sequential designs were used to investigate cultural variables influencing PHB production (central composite sequential design). Results and conclusion Of a total of nine different isolates, three were found to be PHB positive based on the color using Nile Red stain. The potent strain was identified as Bacillus safensis (NR_113945.1). Using one factor at a time experiments, sugar molasses and ammonium sulfate, respectively, were the best carbon and nitrogen sources, whereas the best inoculum was 10 ml/100 ml of fermentation medium. Cultural variables influencing PHB production were studied using Plackett–Burman and central composite sequential designs. Accordingly, the most influential factors on PHB production were sugarcane concentration, inoculum size, and KH2PO4. Under the optimized conditions, a PHB content (93% cell dry weight) of 1.17 folds was attained. Furthermore, the Fourier transform infrared spectroscopy and 1H-NMR results confirmed the produced polymer as PHB. These results give insight into the use of locally isolated bacteria (B. safensis (NR_113945.1) utilizing inexpensive substrate such as sugarcane molasses for PHB production.