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

Abstract

Metabolic activities of four Bacillus strains to transform glucose into hydrogen (H 2 ) and polyhydroxybutyrate (PHB) in two stages were investigated in this study. Under batch culture conditions, Bacillus thuringiensis EGU45 and Bacillus cereus EGU44 evolved 1.67-1.92 mol H 2 /mol glucose, respectively during the initial 3 days of incubation at 37°C. In the next 2 days, the residual glucose solutions along with B. thuringiensis EGU45 shaken at 200 rpm was found to produce PHB yield of 11.3% of dry cell mass. This is the first report among the non-photosynthetic microbes, where the Bacillus spp.-B. thuringiensis and B. cereus strains have been shown to produce H 2 and PHB in same medium under different conditions.

Production of Polyhydroxyalkanoate Co-polymer by Bacillus thuringiensis

“…Bacillus thuringiensis EGU45 (DQ508971) isolated previously in our laboratory was selected for producing H 2 and PHB [5,12]. Corresponding rrs (16S rRNA) gene sequence can be viewed at http://www.ncbi.nlm.nih.gov/ [4].…”

“…For batch-culture H 2 production, 250 ml of different concentrations (0.5, 1.0 and 2.0 %) of glucose in medium of composition (x) in g/l: (i) minimal medium (M-9)-Na 2 HPO 4 , 6.0 g; KH 2 PO 4 , 3.0 g; NaCl, 0.5 g; NH 4 Cl, 1.0 g; MgSO 4 , 1.0 mM and CaCl 2 , 0.1 mM), (ii) Growth medium (GM-2)-Yeast extract, 1.0; K 2 HPO 4 , 1.0 and MgSO 4 Á7H 2 O, 0.5) and (iii) synthetic media (combinations M-9?GM-2) were added in 300 ml BOD bottles [5]. These were inoculated with B. thuringiensis at the rate of 10.0 lg cell protein/ml of glucose solution.…”

“…Biological H 2 production has been recognized as a clean fuel of the future and bioplastics will help to reduce the consumption of fossil fuel based plastics. Production of H 2 and polyhydroxybutyrate (PHB-a class of PHA) in separate reactors and different sets of bacteria from pure substrates such as carbohydrates is limited by the high cost of feed which in turn hinders their production on a large scale for commercial use [5]. Another limiting factor associated with bacterial production of PHB is their brittle nature [2,6].…”

“…Here, the prime need is to look for copolymers which can impart greater strength to biopolymer, utilize a single bacterium and integrate these two processes to generate both the products. Although these concepts have been recognized quite early, however, very limited research has been carried out [5,[7][8][9]. Biological H 2 and PHB production abilities of bacteria have been reported through in silico techniques and through wet experiments as well [4,5,10,11].…”

“…have been reported to produce both H 2 and PHB from glucose and biowastes [5,12,13]. A few Bacillus spp.…”