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

Abstract

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 . 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.

Production of Polyhydroxyalkanoate Co-polymer by Bacillus thuringiensis

“…1.0 % glucose concentration was found optimum for both H 2 and PHA production and use of fresh medium with corresponding glucose promoted new co-polymer to a significant extent. Production of PHA co-polymer has been reported from various Bacillus strains, however, this usually require supplementation of precursor substrates [14,15]. This is the first study of PHA co-polymer production with a new composition that too without supplementation of precursor sources.…”

“…Although production of a wide range of co-polymers of PHA by Bacillus has been reported from pure sugars and biowaste materials [14,15,22,23]. The detection of levulinic acid without any supplement in the feed (glucose) is a new observation.…”

“…have also been shown to produce co-polymers of PHA when co-fed with various substrates. In these works, co-polymer production was reported only from glucose supplemented with respective precursors [14,15].…”

Challenges and Opportunities for Customizing Polyhydroxyalkanoates

“…3HHx. PHAs varying from PHB, P(3HB:3HV), P(3HB:3HHx), P(3HB:4HB:3HHx) to P(3HB:6HHx:3HHx) depending upon the substrate [3,4,30,32,33]. Bacillus provides a robust option as potential PHA producer under more stringent conditions [3,4].…”

Hydrogen and Polyhydroxybutyrate Producing Abilities of Bacillus spp. From Glucose in Two Stage System

“…Under stress conditions, primarily those of magnesium, nitrogen, phosphorus and potassium [25], PHB production is initiated by diversion of acetyl CoA from TCA cycle due to the suppression of citrate synthase and iso-citrate dehydrogenase (key enzymes of TCA cycle) activities leading to blockage of TCA cycle. High acetyl CoA concentration and low CoA activates b-ketothiolase which converts acetyl CoA to aceto-acetyl CoA, which is then converted to 3-hydroxybutyryl CoA through the action of aceto-acetyl CoA reductase.…”