Investigating and modelling the effect of light intensity on Rhodopseudomonas palustris growth

Light Penetration ◽

Tubular Photobioreactor ◽

Photobioreactor Design ◽

High Purity Hydrogen ◽

Photosynthetic bacteria can be useful biotechnological tools – they produce a variety of valuable products, including high purity hydrogen, and can simultaneously treat recalcitrant wastewaters. However, while photobioreactors have been designed and modelled for photosynthetic algae and cyanobacteria, there has been less work on understanding the effect of light in photosynthetic bacterial fermentations. In order to design photobioreactors, and processes using these organisms, robust models of light penetration, utilisation and conversion are needed. This article uses experimental data from a tubular photobioreactor designed to focus in on light intensity effects, to model the effect of light intensity on the growth of Rhodopseudomonas palustris, a model photosynthetic bacterium. The work demonstrates that growth is controlled by light intensity, and that this organism does experience photoinhibition above 600 W/m2, which has implications for outdoor applications. Further, the work presents a model for light penetration in circular photobioreactors, which tends to be the most common geometry. The work extends the modelling tools for these organisms, and will allow for better photobioreactor design, and the integration of modelling tools in designing processes which use photosynthetic bacteria.

Effect of Light Intensity on Schottky Barrier Widths and I-V Characteristics of Polymer Heterojunction Photodiodes

MRS Proceedings ◽

10.1557/opl.2011.1015 ◽

2011 ◽

Vol 1359 ◽

Cited By ~ 1

Author(s):

Ali Bilge Guvenc ◽

Cengiz Ozkan ◽

Mihrimah Ozkan

Keyword(s):

Experimental Data ◽

Light Intensity ◽

Mathematical Models ◽

Schottky Barrier ◽

Butyric Acid ◽

Organic Semiconductor ◽

Schottky Barriers ◽

Light Intensities ◽

ABSTRACTThe Schottky barriers that forms on the interface between aluminum and organic semiconductor of polymer heterojunction photodiodes based on poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methylester blend, has been investigated according to Mott-Schottky curves. We focused on the effect of light intensity on the Schottky barrier widths and I-V characteristics of the devices. Comparison of the mathematical models and experimental data measured under different light intensities indicate a dependency of Schottky barrier to the light intensity.

Immobilization and Ammonia Removal of Photosynthetic Bacteria

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.610-613.311 ◽

2012 ◽

Vol 610-613 ◽

pp. 311-314 ◽

Cited By ~ 1

Author(s):

Pei Rong Zhan ◽

Wei Liu

Keyword(s):

Electron Microscopy ◽

Amino Acids ◽

Photosynthetic Bacteria ◽

Carbon Sources ◽

Water Environment ◽

Ammonia Removal ◽

Fish Pond ◽

Immobilized Microorganisms

The photosynthetic bacteria have been widely used in improving the water environment, especially for pollutant purification. A photosynthetic bacterium was isolated from fish pond sludge using various methods. The bacterium is rod-shaped and slightly curved, and they reproduce by budding. It grew anaerobically when exposed to light and aerobically in darkness. Based on electron microscopy, utilization of carbon sources and amino acids, and factors required for growth, the bacterium is identified as Rhodopseudomonas palustris. The R. palustris was immobilized using different carriers to increase its concentration and its targeted use. The results show that immobilization of the bacteria stabilized the ammonia removal and protected the bacteria from predation by plankton. The method is also easy to use and prolonged the purification effect in the reactor. The immobilized microorganisms are 30%–40% more effective than free bacteria in removing ammonia.

The light intensity under which cells are grown controls the type of peripheral light-harvesting complexes that are assembled in a purple photosynthetic bacterium

Biochemical Journal ◽

10.1042/bj20110575 ◽

2011 ◽

Vol 440 (1) ◽

pp. 51-61 ◽

Cited By ~ 23

Author(s):

Tatas H. P. Brotosudarmo ◽

Aaron M. Collins ◽

Andrew Gall ◽

Aleksander W. Roszak ◽

Alastair T. Gardiner ◽

...

Keyword(s):

Light Intensity ◽

Light Harvesting ◽

Low Light ◽

Light Harvesting Complexes ◽

Density Maps ◽

Purple Photosynthetic Bacterium ◽

Resonance Raman Spectra ◽

Apoprotein Composition

The differing composition of LH2 (peripheral light-harvesting) complexes present in Rhodopseudomonas palustris 2.1.6 have been investigated when cells are grown under progressively decreasing light intensity. Detailed analysis of their absorption spectra reveals that there must be more than two types of LH2 complexes present. Purified HL (high-light) and LL (low-light) LH2 complexes have mixed apoprotein compositions. The HL complexes contain PucABa and PucABb apoproteins. The LL complexes contain PucABa, PucABd and PucBb-only apoproteins. This mixed apoprotein composition can explain their resonance Raman spectra. Crystallographic studies and molecular sieve chromatography suggest that both the HL and the LL complexes are nonameric. Furthermore, the electron-density maps do not support the existence of an additional Bchl (bacteriochlorophyll) molecule; rather the density is attributed to the N-termini of the α-polypeptide.

Redirection of Metabolism for Biological Hydrogen Production

Applied and Environmental Microbiology ◽

10.1128/aem.02565-06 ◽

2007 ◽

Vol 73 (5) ◽

pp. 1665-1671 ◽

Cited By ~ 103

Author(s):

Federico E. Rey ◽

Erin K. Heiniger ◽

Caroline S. Harwood

Keyword(s):

Nitrogen Fixation ◽

Hydrogen Production ◽

Photosynthetic Bacteria ◽

Selection Strategy ◽

Wild Type ◽

Purple Photosynthetic Bacteria ◽

Mutant Strains ◽

Different Strains

ABSTRACT A major route for hydrogen production by purple photosynthetic bacteria is biological nitrogen fixation. Nitrogenases reduce atmospheric nitrogen to ammonia with the concomitant obligate production of molecular hydrogen. However, hydrogen production in the context of nitrogen fixation is a rather inefficient process because about 75% of the reductant consumed by the nitrogenase is used to generate ammonia. In this study we describe a selection strategy to isolate strains of purple photosynthetic bacteria in which hydrogen production is necessary for growth and independent of nitrogen fixation. We obtained four mutant strains of the photosynthetic bacterium Rhodopseudomonas palustris that produce hydrogen constitutively, even in the presence of ammonium, a condition where wild-type cells do not accumulate detectable amounts of hydrogen. Some of these strains produced up to five times more hydrogen than did wild-type cells growing under nitrogen-fixing conditions. Transcriptome analyses of the hydrogen-producing mutant strains revealed that in addition to the nitrogenase genes, 18 other genes are potentially required to produce hydrogen. The mutations that caused constitutive hydrogen production mapped to four different sites in the NifA transcriptional regulator in the four different strains. The strategy presented here can be applied to the large number of diverse species of anoxygenic photosynthetic bacteria that are known to exist in nature to identify strains for which there are fitness incentives to produce hydrogen.

Investigating and modelling the effect of light intensity on Rhodopseudomonas palustris growth

Biotechnology and Bioengineering ◽

10.1002/bit.28026 ◽

2021 ◽

Author(s):

Brandon Sean Ross ◽

Robert W.M. Pott

Keyword(s):

Light Intensity ◽

Effect of light intensity on the ultrastructure of the filamentous cyanobacterium, Anabaena variabilis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103565 ◽

1988 ◽

Vol 46 ◽

pp. 300-301

Author(s):

C. S. Bricker ◽

S. R. Barnum ◽

B. Huang ◽

J. G. Jaworskl

Keyword(s):

Fatty Acid ◽

Light Intensity ◽

Acid Content ◽

Fatty Acid Content ◽

Anabaena Variabilis ◽

Chloroplast Envelope ◽

Major Constituent ◽

Filamentous Cyanobacterium ◽

Photosynthetic Membrane ◽

Cyanobacteria are Gram negative prokaryotes that are capable of oxygenic photosynthesis. Although there are many similarities between eukaryotes and cyanobacteria in electron transfer and phosphorylation during photosynthesis, there are two features of the photosynthetic apparatus in cyanobacteria which distinguishes them from plants. Cyanobacteria contain phycobiliproteins organized in phycobilisomes on the surface of photosynthetic membrane. Another difference is in the organization of the photosynthetic membranes. Instead of stacked thylakolds within a chloroplast envelope membrane, as seen In eukaryotes, IntracytopIasmlc membranes generally are arranged in three to six concentric layers. Environmental factors such as temperature, nutrition and light fluency can significantly affect the physiology and morphology of cells. The effect of light Intensity shifts on the ultrastructure of Internal membrane in Anabaena variabilis grown under controlled environmental conditions was examined. Since a major constituent of cyanobacterial thylakolds are lipids, the fatty acid content also was measured and correlated with uItrastructural changes. The regulation of fatty acid synthesis in cyanobacteria ultimately can be studied if the fatty acid content can be manipulated.