Flexible plastic bioreactors for photobiological hydrogen production by hydrogenase-deficient cyanobacteria.
ABSTRACT Uptake hydrogenase mutant cells of the cyanobacterium Nostoc sp. PCC 7422 photobiologically produced H(2) catalyzed by nitrogenase for several days in H(2)-barrier transparent plastic bags, and accumulated H(2) in the presence of O(2) evolved by photosynthesis. Their H(2) production activity was higher in the sealed flexible bags than in stoppered serum bottles of fixed gas volume.
- [Show abstract] [Hide abstract]
ABSTRACT: We describe a convenient and inexpensive latex wet coalescence extrusive coating method that produces up to 10-fold specific photosynthetic rate enhancements by non-growing cyanobacteria deposited onto paper. These plant leaf-like biocomposites were used to study tolerance of cyanobacteria strains to illumination and temperature using a solar simulator. We report sustained CO2 absorption and O2 production for more as 500 hours by hydrated gas-phase paper coatings of non-growing Synechococcus PCC7002, Synechocystis PCC6803, Synechocystis PCC6308 and Anabaena PCC7120. The average CO2 consumption rate in Synechococcus coatings is 5.67 mmol m−2 h−1 which is lower compared to the rate reported in the literature for Arabidopsis thaliana leaves under similar experimental conditions (18 mmol m−2 h−1), but yet surprisingly close considering the simplicity of the coating method. We observed ratios of oxygen production to carbon dioxide consumption (photosynthetic quotient, PQ) between 1.3-1.4 which may indicate a strong dependence on nitrate assimilation during growth and was used to develop a non-growth media formulation for intrinsic kinetics studies. Photosynthetic Intensification Factors (PIF) (the ratio of O2 production by nitrate-limited microalgae in latex coatings divided by O2 produced by nitrate-limited cell suspensions) in cyanobacteria composites prepared from wet cell pellets concentrated 100 to 300 fold from suspension cultures show 7-10 times higher specific reactivity compared to cells in suspension under nitrate-limited non-growth conditions for the same strains. This is the first report of changes of microalgae tolerance to temperature and light intensities after deposition as a thin coating on a porous matrix, which has important implications for photobioreactor design using porous composite materials. Cryo-fracture SEM and confocal microscopy images of cell coating distribution on the paper matrix and composite microstructure suggest that the spatial arrangement of the cells in the coating can affect the photoreactivity of the biocomposite. This technique could be used to fabricate multi-organism composite coatings on flexible microfluidic devices capable of harvesting light in a broader range of wavelengths, to optimize coatings of thermotolerant, desiccation tolerant or halotolerant cyanobacteria strains that produce O2 with secretion of liquid-fuel precursors synthesized from CO2. Biotechnol. Bioeng. © 2014 Wiley Periodicals, Inc.Biotechnology and Bioengineering 06/2014; · 4.16 Impact Factor