Polyhydroxyalkanoate biosynthesis in Bacillus cereus SPV under varied limiting conditions and an insight into the biosynthetic genes involved.

AIMS: A new strain of Bacillus, Bacillus cereus SPV, was found to be capable of using a wide range of carbon sources for the production of polyhydroxyalkanoates (PHAs) (Valappil et al. 2007b). Limiting nutrient in the culture conditions is crucial for PHA production. In this study, B. cereus SPV was grown in different culture conditions with limitation of potassium, nitrogen, sulphur and phosphorous to establish the impact of nutritional limitation on PHA production. METHODS AND
RESULTS: The PHA yields obtained were found to be 13.4, 38, 13.15 and 33.33% dcw for potassium, nitrogen, sulphur and phosphorus limitations, respectively. Gas chromatography-mass spectrometry analysis of the isolated polymers showed the presence of P(3HB) under nitrogen, sulphur and phosphate-limiting conditions and P(3HB-3HV) copolymer under potassium limiting conditions. This ability of B. cereus SPV to accumulate different PHA monomers from structurally unrelated carbon sources led to an interest in the molecular analysis of PHA biosynthesis in this organism. To achieve this, PCR was used to identify the polyhydroxyalkanoate biosynthetic genes in B. cereus SPV.
CONCLUSION: Sequence analysis of the PCR products from B. cereus SPV revealed the sequence of the putative biosynthetic genes, and possible regions involved in substrate binding. The nucleotide sequence reported in this paper is in the GenBank nucleotide sequence database under accession number DQ486135. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report comparing the capability of B. cereus SPV to produce PHAs under different culture conditions of potassium, nitrogen, sulfur and phosphate limitations. The results in this study suggest the unique ability of B. cereus SPV to supply both 3HB and 3HV monomers from a structurally unrelated carbon source, glucose.