ISSN 2630-0583 (Print)
ISSN 2630-0656 (Online)
Journal of Current Science and Technology
Rangsit Journal of Arts and Sciences. Vol.6 No.1 , January - June 2016.
Isolation of Bacillus cereus C042 capable of producing polyhydroxybutyrate (PHB) by using unhydrolysed waste from rice bran oil production as carbon source
A replacement of polyhydroxyalkanoates (PHAs) for existing petroleum-based plastics is limited due to their high production cost. Thus, increased production of PHAs on cheap substrates is an important challenge to support the commercialization. Normally, the pre-treatment of cheap substrates is required which results in increased costs and time. In this study, native rice bran waste materials from rice bran oil production, using the cold press method which generates various fatty acids, were used as the main carbon source for poly(3-hydroxybutyrate) (P(3HB)) production. Fifty soil samples obtained from various locations in Thailand, including industrial sites, refuse sites, garden and community areas, were screened for PHAs-producing microorganisms. Each soil sample was diluted in distilled water and the soil suspension was poured on MSA agar supplemented with 3% (w/v) native rice bran waste materials. The microorganisms that grew on the medium were further screened for PHAs production by using Sudan Black B staining. The production of P(3HB) was confirmed by using Gas Chromatography-Mass Spectrometry (GC-MS) by comparing to standard P(3HB). The P(3HB) content was measured by using GC and percentage of P(3HB) content per cell dry weight was calculated. It was found that 55 of 336 isolates (16.4%) which grew were positive for PHAs. The isolate designated C042 showed the highest potential for PHAs production and was used for further experiments. Biopolymer was extracted from C042 dried cells by using chloroform. From GC-MS analysis, it was found that biopolymer was P(3HB) by comparing the mass spectrum to standard P(3HB). The isolate C042 was gram positive bacilli with spore forming abilities and was further identified as Bacillus cereus by using 16S RNA sequencing method. The percentage of P(3HB) production per cell dry weight of Bacillus cereus C042 was 11.6 (w/w) when the cells were grown on MSA agar supplemented with 21% (w/v) native rice bran waste materials.