Production of Free Amino Acid by Three Anoxygenic Phototrophic Purple Bacteria (original) (raw)
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Production of amino acids by free-living heterotrophic nitrogen-fixing bacteria
Amino Acids, 1995
Interest of microbial production of amino acids has been increased greatly since development of biotechnological methods. These methods represent a perspective way applied in a future large-scale manufacture of inexpensive amino acids. In this context, the isolation of producing organisms that may be exploited in the desing of alternative methods for the production of amino acids could be of primary importance.
FEMS Microbiology Letters, 1986
The halophilic phototrophic bacterium Rhodospirillum salexigens was tested for growth on a variety of organic and inorganic nitrogenous compounds as sole nitrogen sources. In media containing acetate as carbon source, the amino acids glutamate, proline, and aspartate supported good growth of R. salexigens; several other amino acids or ammonia did not support growth. Attempts to grow R. salexigens on ammonia led to the discovery that this organism excretes a highly basic substance under certain nitrogen nutritional conditions which raises the pH above that supporting growth. Cultures of K salexigens transferred to media containing both pyruvate and acetate as carbon sources grew on ammonia as sole nitrogen source and the culture pH did not rise. Dual substrate experiments showed that R. salexigens utilized glutamate in preference to ammonia when both were present at equimolar concentrations.
Populations of phototrophic purple nonsulfur bacteria (PNSB) of up to 10 4 –10 7 CFU ml 1 were found in photo-synthetic sludge and activated sludge plants treating wastewater having different biological oxygen demand (BOD) levels and containing acetate as a main BOD source. There was a positive correlation between the population density of PNSB and the strength of BOD in the aeration tanks. All of the PNSB strains isolated were identified as species of the genera Rhodobacter and Rhodopseudomonas by 16S rRNA gene sequencing. The Rhodobacter species were abundant in high BOD-loaded wastewater environments, while the Rhodopseudomo-nas species increased at lower BOD levels. Therefore, the PNSB population structure appeared to be greatly affected by the concentration of lower fatty acids as major BOD sources, varying over time and space. The utilization of lower fatty acids with different carbon numbers (C2 to C6) by aerobically or semi-aerobically grown cells of authentic and isolated PNSB strains was evaluated by monitoring substrate-dependent oxygen uptake. The oxidation of the fatty acids by the Rhodobacter strains depended upon the number of carbons in the substrate, while the Rhodopseudomonas strains utilized all substrates equally. A low carbon number was much preferred by the Rhodobacter strains. The affinity for acetate of the Rhodobacter and Rhodopseudomonas strains ranged from 0.14 to 3.0 mM and 0.032 to 0.096 mM, respectively. These results suggest that the concentration and kind of lower fatty acids as major BOD sources are important factors affecting not only the population level but also the species composition of PNSB in wastwater environments.
Liberation of amino acids by heterotrophic nitrogen fixing bacteria
Amino Acids, 2005
Large amounts of amino acids are produced by nitrogen-fixing bacteria such as Azotobacter, Azospirillum, Rhizobium, Mesorhizobium and Sinorhizobium when growing in culture media amended with different carbon and nitrogen sources. This kind of bacteria live in close association with plant roots enhanced plant growth mainly as a result of their ability to fix nitrogen, improving shoot and root development suppression of pathogenic bacteria and fungi, and increase of available P concentration. Also, it has been strongly evidenced that production of biologically substances such as amino acids by these rhizobacteria are involved in many of the processes that explain plant-grown promotion. This paper reviews literature concerning amino acids production by nitrogen-fixing bacteria. The role of amino acids in microbial interactions in the rhizosphere and establishment of plant bacterial association is also discussed.
Purple phototrophic bacteria for resource recovery: Challenges and opportunities
Biotechnology Advances, 2020
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Hrvatski Časopis za Prehrambenu Tehnologiju Biotehnologiju i Nutricionizam - Croatian Journal of Food Technology, Biotechnology and Nutrition, 2017
Wild strains of purple non-sulphur bacteria: Rhodospirillum rubrum B-6505, Rhodopseudomonas palustris B-6506, Rhodobacter capsulatus B-6508 and Rhodobacter spheroides B-6509 were studied as 5-ALA (5 aminolevulinic acid) producers. Selected strains were subjected to mutagenesis with N-methyl-N-nitro-N-nitrosoguanidine to obtain a strain with high 5-ALA producing capacity. After mutagenesis 19 stable mutant strains were selected from Rhodobacter capsulatus B-6508 and Rhodobacter sphaeroides B-6509. On the basis of obtained results, mutant strain of Rhodobacter capsulatus B-6508 has shown the highest potential for 5-ALA production. The most favorable conditions for growth and 5-ALA production by mutant strain R. capsulatus B-6508 were observed in media composed of glutamate and malate, light at 2000 Lux, microaerophilic conditions and temperature of 28 °C. In these conditions, the highest 5-ALA concentration (179 mg/L) was detected together with the highest bacterial physiological acti...
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Domestic wastewater treatment by purple phototrophic bacteria (PPB) is based on the assimilative uptake of organics and nutrients into the bacterial biomass. Thereby, it strongly depends on the carbon/nutrients ratio of the wastewater. The physiological COD/N/P ratio for PPB growth in domestic wastewater makes the addition of an external organic carbon source necessary in order to allow for an efficient process. However, PPB need a source of alkalinity (as CO2) to grow on reduced organics that serves as an electron acceptor since biohydrogen production (an alternative electron sink) is inhibited by ammonium. A preliminary experiment showed that high nutrients-loading wastewater was limited by CO2 imbalance, leading to poor removal efficiencies. Subsequently, the effect of the oxidation state of the organics added as external organic carbon sources to PPB reactors treating low nutrients-loading domestic wastewater has been analyzed. Three organics were used as additives to PPB develo...
World Journal of Microbiology and Biotechnology, 2007
Hydrogen is the fuel for the future, mainly due to its recyclability and nonpolluting nature. Biological hydrogen production processes are operated at ambient temperature and atmospheric pressures, thus are less energy intensive and more environmentally friendly as compared to thermochemical and electrochemical processes. Biohydrogen processes can be broadly classified as: photofermentation and dark fermentation. Two enzymes namely, nitrogenase and hydrogenase play an important role in biohydrogen production. Photofermentation by Purple Non-Sulfur bacteria (PNS) is a major field of research through which the overall yield for biological hydrogen production can be improved significantly by optimization of growth conditions and immobilization of active cells. The purpose of this paper is to review various processes of biohydrogen production using PNS bacteria along with several current developments. However, suitable process parameters such as carbon and nitrogen ratio, illumination intensity, bioreactor configuration and inoculum age may lead to higher yields of hydrogen generation using PNS bacteria. Keywords Purple non-sulfur (PNS) bacteria AE Biohydrogen AE Photofermentation AE Bioreactor AE Nitrogenase AE Hydrogenase Nomenclature B.C.-I Bacteriochlorophyll-I Cyt Cytochrome E eff Efficiency of light energy conversion (%) Fd (ox) Ferredoxin (oxidized form) Fd (red) Ferredoxin (reduced form) DG o ¢ Gibb's free energy (kJ mol-1) k c Apparent specific growth rate (h-1) LH-I Light harvesting I antenna complex MSW Municipal solid wastes PVA Polyvinyl alcohol RC Reaction center t Time (h) x Cell dry mass conc (g l-1) dx/dt Rate of change of cell dry mass conc (g l-1 h-1) x max Maximum cell dry mass conc (g l-1) Greek letters l Specific growth rate (h-1) l e Specific growth rate constant in exponential phase (h-1