Production of Polyhydroxyalkanoate by Local Strain of Bacillus megaterium AUMC b 272 Utilizing Sugar Beet Wastewater and Molasses

Abstract

Development of polyhydroxyalkanoates (PHAs) as a potential substitute material to some conventional plastics has drawn much attention due to their biodegradable and compatible properties. The potential applications of PHA in various industries and in the medical field are encouraging. Nevertheless, the production cost of PHA has been a major drawback. Consequently, scientific effort have been made to overcome the high cost of the substrates used in the bio-production. In this study, sugar beet industry wastewater without and with beet molasses was used as potential low cost substrate for production of the biopolymer PHA by a local bacterial strain. This strain was selected after screening of 30 bacterial isolates for PHA production and was identified according to 16S rRNA gene sequencing as Bacillus megaterium AUMC b 272. The maximum PHA formed by this strain reached to 4.053 g/L with a recovery yield equal to 41.79 % of the bacterial biomass using modified mineral salt medium (MSM) medium containing 6 % beet molasses as sole carbon source and 0.5 g/L ammonium oxalate as a nitrogen source. The initial pH of the medium was adjusted at 8.5. Cultures were incubated at 200 rpm and 37o C for 24 hrs. On the other hand, the bacterial strain produced negligible levels of PHA when grown on the same medium constituents under the same conditions with replaced distilled water and molasses by sugar beet wastewater. While the PHA concentration reached to 0.828 g/L with 46 Zohri A. A. et al (2019) Egyptian Sugar Journal, .Vol.13 ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ recovery yield 20.58 % of biomass in the same medium under the same conditions after replacement of distilled water by sugar beet wastewater. It is worthy to mention that the COD in the sugar beet wastewater medium at the end of fermentation period was removed by 69 %. Characterization of the obtained PHA was achieved using Fourier transform-infra-red spectroscopy (FT-IR) and gas chromatograph mass spectrometric (GCMS). Accumulation of considerable levels of PHA as well as high levels of COD removal from sugar beet wastewater strongly introduced this biotechnological process as valuable method for production of PHA as biodegradable biopolymer from sugar beet industry wastewater in presence of beet molasses as potential low cost substrates and, at the same time, for biological treatment of industry wastewater.