Relationship between the photoproduction of hydrogen and the accumulation of PHB in non-sulphur purple bacteria

Abstract

Wild-type cells of Rhodobacter sphaeroidesand Rhodospirillum rubrum strains Ha and S1 as well as mutant cells defective in the synthesis of poly-(3-hydroxybutyric acid) (PHB), were used to study the competition between PHB accumulation and photoproduction of hydrogen for reducing equivalents. Mutants were isolated after transposon (Tn5) or N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. The PHB-defective mutants of R. sphaeroides lacked PHB synthase activity. In two mutants Tn5 was inserted in the PHB synthase gene. No mutants occurred that lacked the activity of fl-ketothiolase or acetoacetyl-coenzyme A reductase. Pronounced competitive effects occurred only with acetate as the organic substrate. With other organic acids or sugars, which are less readily converted to PHB than acetate, competitive effects were not significant or absent.

Investigation of the Photoheterotrophic Hydrogen Production of <i>Rhodobacter sphaeroides</i> KCTC 1434 using Volatile Fatty Acids under Argon and Nitrogen Headspace

“…First, it requires Adenosine Triphosphate (ATP) and reducing power in the form of NADPH 2 which diminishes energy and electron output; and second, it shares common elements with Polyhydroxybutyrate (PHB) biosynthetic route (Kars and Gunduz, 2010). The production of polyhydroxyalkanoates (e.g., PHB) as an intracellular storage material is another route that competes with the H 2 production in disposing excess reducing equivalents in cells (Hustede et al, 1993). PHB production is often seen as one of the critical factors associated with low H 2 productivity during utilization of organic substrate in photo fermentation (Khatipov et al, 1998;Kobayashi et al, 2011;Koku et al, 2002;Han et al, 2012;Pandey et al, 2012).…”

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

“…Use of undefined microbial mixtures for H 2 production process, is likely to produce high variability among the intermediates, which are to be used for the next step of PHB production. To the best of our knowledge, till date only three photosynthetic organisms have been reported with abilities to produce these two bioproducts H 2 and PHA: R. palustris, R. rubrum and R. sphaeroides [16][17][18][19]. Here, it is the first demonstration of producing H 2 and PHB with the same strain of non-photosynthetic bacterium, Bacillus in a sequential manner without any further addition of nutrients or bacteria during the second stage of PHB production.…”

“…Recent efforts to produce H 2 and PHB from a single organism have been limited to a few photosynthetic organisms: Rhodopseudomonas palustris strain 42OL, Rhodospirillum rubrum strains Ha and S1, and R. sphaeroides O.U. 001 [16][17][18][19]. Among the dark fermentative bacteria quite a few species are known to produce both the bioproducts: H 2 and PHB [2,9].…”

Integrating dark and light bio-hydrogen production strategies: towards the hydrogen economy

“…Mutagenesis of the PHB synthase gene yielded PHB deficient mutants, which were capable of H 2 production under conditions that would normally favour PHB synthesis (Hustede et al 1993) (Table 2). In recent studies, double mutants lacking uptake hydrogenase and also PHB synthase produced H 2 at up to 2.5-fold higher rates compared to the parent strain (Lee et al 2002;Kim et al 2006b), while in a separate study a similar double mutant sustained H 2 production for over 45 days, while the wild-type ceased H 2 production after 10 days (Franchi et al 2004).…”

“…Develop PHB deficient strains Proven at pilot-scale (Hustede et al 1993;Lee et al 2002;Franchi et al 2004;Kim et al 2006b Recirculation of headspace gas…”