Growth Of Photosynthetic Bacteria Research Articles

Effects of dissolved oxygen on key enzyme activities during photosynthetic bacteria wastewater treatment

Abstract Photosynthetic bacteria (PSB) wastewater treatment is a novel method that can simultaneously achieve wastewater purification and recourse recovery. Oxygen conditions can significantly influence PSB metabolism and wastewater treatment; however, the roles of key enzymes in this process have been unclear. This study investigated the effects of different oxygen conditions on respiratory enzymes (hexokinase, HK; phosphofructokinase, PFK; and pyruvate kinase, PK) and the photosynthetic enzyme RuBisCO of PSB. The results showed that HK activity was almost the highest under anaerobic condition; PFK activity was the highest (311 nmol/min∙g) and PK the most quickly reached its peak under aerobic condition; and RuBisCO activity was the highest (107 nmol/min g) under anaerobic condition. The above results illustrated that HK might simultaneously regulate PSB growth and COD degradation, and its main role might be PSB growth regulation. PFK and PK might function in COD degradation while RuBisCO might function in PSB growth. Further, oxygen was beneficial for COD degradation and detrimental for PSB growth. This study provides a theoretical basis for the development of PSB wastewater treatment.

One-step treatment and resource recovery of high-concentration non-toxic organic wastewater by photosynthetic bacteria

In order to achieve simple pollutant removal and simultaneous resource recovery in high-COD-non-toxic wastewater treatment, a one-step photosynthetic bacteria (PSB) method was established using batch study experiment. The effluent COD met the national discharge standard, and biomass with rich protein and high-value substances was efficiently produced. It eliminated the demand of post-treatment for conventional PSB treatment. Results showed that Rhodopseudomonas effectively treated brewery wastewater and achieved biomass proliferation. Yeast extract was the best additive for PSB growth and the effluent COD was below 80 mg/L with 400 mg/L yeast extract, meeting the national discharge standard. In addition, the PSB biomass increased by 2.6 times, and the cells were rich in protein, polysaccharide, carotenoids, bacteriochlorophyll and coenzyme Q10, reaching 420.9, 177.6, 2.53, 10.75 and 38.6 mg/g respectively. This work demonstrated the great potential of PSB for high-COD non-toxic wastewater treatment in one-step process.

Effects of dissolved oxygen concentration on photosynthetic bacteria wastewater treatment: Pollutants removal, cell growth and pigments production

Dissolved oxygen (DO) is an important parameter in photosynthetic bacteria (PSB) wastewater treatment. This study set different DO levels and detected the pollutants removal, PSB growth and pigments production. Results showed that DO significantly influenced the performances of PSB wastewater treatment process. The highest COD (93%) and NH3-N removal (83%) was achieved under DO of 4–8mg/L, but DO of 2–4mg/L was recommended considering the aeration cost. PSB biomass reached 1645mg/L under DO of 4–8mg/L with satisfying co-enzyme Q10 content. The biomass yield was relatively stable at all DO levels. For bacteriochlorophyll and carotenoids, DO>1mg/L could satisfy their production. On the other hand, DO<0.5mg/L led to the highest dehydrogenase activity. According to the different purposes, the optimal treatment time was different. The most pigments production occurred at 24h; biomass reached peak at 48h; and the optimal time for pollutants removal was 72h.

A biomaterial doped with LaB6 nanoparticles as photothermal media for enhancing biofilm growth and hydrogen production in photosynthetic bacteria

A novel photothermal biomaterial, designated GeO2-SiO2-Chitosan-Medium-LaB6 (GSCML), was prepared to improve photosynthetic bacteria (PSB) biofilm development and hydrogen production performance. This biomaterial employed spectral beam splitting technology to increase the overall utilization of the incident light spectrum, which LaB6 nanoparticles (NPs) mainly absorb light at approximately 380–510 and 660–780 nm and convert it into heat energy; the transmit light is around 590 nm for PSB growth. The temperature increased, and the luminous intensity of the light transmitted through the prepared biomaterial are controlled by adjusting the LaB6 NPs' content. The average biofilm growth rate and hydrogen production rate of the biofilm on the created biomaterial were 0.05 mg/cm2/day and 2.92 mmol/h/m2, which were 3.4 and 4.1 times higher than those of the glass slide, respectively. The properties of the GSCML biomaterial provide advantages for applications in immobilized cell technologies and photobioreactors.

English

In order to promote the growth of photosynthetic bacteria (PB) use as biofertilizers in paddy fields, this study conducted during 2011 to 2012 at Department of Agricultural Microbiology, University of Agricultural Sciences, Dharwad, Karnataka, India. Twenty phototrophic purple non-sulphur bacterial (PPNSB) isolates were isolated from paddy rhizosphere soils of Northern Karnataka. Isolates were tested by morphologically, biochemically and physiologically according in to Bergey’s manual. All the isolates belong to PPNSB Rhodobacter sp. In vitro nitrogen fixation was estimated by percent nitrogen content in cells which were grown on nitrogen free culture broth. Maximum percent nitrogen content was recorded in culture broth inoculated with isolate NKPRSR -1 (2.50%). Based on percent nitrogen content, the best five efficient isolates were selected for hydroponic culture to see the effect on paddy seedlings growth under laboratory condition. In hydroponics Complete Randomized Design was used to accommodate 13 treatments with 5 replication, with the combination of nitrogen source and without nitrogen sources. Results revealed that treatment having isolate Rhodobacter sp. NKPRSR 1+ Nitrogen source show maximum plant height (26.67 cm), root length (13.17 cm), dry weight (16.50 mg/ plant) and percent nitrogen content (0.99%) after 30 days of sowing. Key words: Isolation, purple nonsulphur bacteria, paddy, hydroponics, rhodobacter, rhizosphere.

Enhanced photosynthetic hydrogen production performance of Rhodobacter capsulatus by deactivating CBB cycle and cytochrome c oxidase

The effect of redox balance on photosynthetic bacteria growth and hydrogen generation is significant since it affects the distribution of electron flow. In this study, cbbP encoding the key enzymes in CO2 fixation cycle, and ccoNOQP encoding cyt cbb3 oxidase in cytochrome respiratory chain, were knocked out from the genome of Rhodobacter capsulatus SB1003 to obtain the mutants Wb301 (ΔccoNOQP), Wbp02 (ΔcbbP) and W3p03 (ΔcbbP, ΔccoNOQP). The transcriptional and translational level of nifH gene showed that the nifH expression levels in Wb301 and W3p03 were enhanced by 93.5% and 62.5%, and the activities of nitrogenase of Wb301 and W3p03 were enhanced by 30% and 10%, compared with those of wild type strain, respectively. In 60 mL reactors, the hydrogen yields of Wb301 and W3p03 increased by 44.8% and 36.0%, and the maximum hydrogen evolution rates increased by 15.8% and 41.7% compared with that of the wild type, respectively. The mechanisms of CBB and cytochrome c oxidase deactivation on the growth and hydrogen production performance were discussed.

Effect of Substrate pH Value on Hydrogen Production by Photosynthetic Bacteria*

For exploring the hydrogen production mechanism of photosynthetic bacteria,hydrogen production by the purple non-sulfur phototrophic bacterium Rhodoseudomonas palustris CQK-01 illuminated by light-emitting diodes with light wavelength of 470 nm was experimentally investigated in batch culture mode under anaerobic conditions,and the effect of initial substrate pH value on hydrogen production performance and energy conversion efficiencies were discussed.Glucose with concentration of 75 mmol/L was used as carbon source in medium,and the initial substrate pH values were set at 5.5,6.0,7.0,8.0 and 9.0.The light intensity was set at 1 000 lx and operation temperature was 30 ℃.The experimental results showed that the weak alkaline condition was favorable for the growth of photosynthetic bacteria,and after 96 hours' operation for hydrogen production,the total hydrogen production and the maximum hydrogen production rate was 8.0 mmol and 3.39 mmol g-1(cell dry weight) h-1 at the optimal pH 7.0,respectively.The produced hydrogen purity was 70%,and the substrate energy conversion efficiency and light energy conversion efficiency were 1.98% and 7.7%,respectively.It was also found that the substrate energy conversion efficiency,light energy conversion efficiency,hydrogen production and hydrogen production rate were higher in acidic substrate than in alkaline substrate,while the hydrogen purity increased with the increase of initial substrate pH value

Influences of light and oxygen conditions on photosynthetic bacteria macromolecule degradation: Different metabolic pathways

Direct degradation of macromolecules by photosynthetic bacteria (PSB) is important for the industrial application of PSB wastewater treatment. Light and oxygen are the most important parameters in PSB growth. This paper studied the PSB macromolecule degradation process under three different light and oxygen conditions: light-anaerobic, natural light-microaerobic and dark-aerobic. The results showed that under three different light-oxygen conditions, PSB degradation of macromolecules was higher than 90%; the removal ratios of COD, TN, TP, total sugar and protein were also high; and the biomass yield reached nearly 0.5mg-biomass/mg-COD-removal. Light and oxygen significantly influenced the efficiency. Macromolecules and pollutants removals were higher under oxygen condition than those under light-anaerobic condition. Theoretical analysis showed that under aerobic condition, PSB carried out oxidative phosphorylation, in which pollutants were sufficiently utilized with high mineralization degree. Under light-anaerobic condition, PSB carried out photophosphorylation and fermentation, which led to low pollutants removal efficiency.

Culture Medium Optimization for Photosynthetic Bacteria

Photosynthetic bacteria (PSB) have various applications but the culture cost is very expensive. To find an efficient and economic culture medium the effects of yeast extract, C/N ratio, and trace elements on the growth of PSB were studied. The results showed that the optimal condition for PSB growth was: yeast extract of 100mg/l, C/N of 12:1, and trace elements (in mol/L): Mn2 + (0.009), Fe3+ (0.0025), Co2+ (0.0024), Cu2 + (0.0024), and Zn2 + (0.0033). Trace element lack could affect the growth of PSB. The order was Mn2 +&gt; Fe3 +&gt; Co2+&gt; Cu2 +&gt; Zn2 +. The improved medium was named HCH, and the optimum medium components were (in g/l) DL-malic acid: (4), MgSO4: (0.12), (NH4)2 SO4: (1), CaCl2: (0.075), KH2PO4: (0.5), K2HPO4: (0.3), Na2EDTA: (0.02), yeast extract : (0.1), trace elements 1ml (in mol/l ): Fe3+: (0.0025), Mn2+: (0.009), Zn2+: (0.0033), Co2+: (0.0024), pH:6.8. Comparing with the traditional RCVBN medium, in HCH medium yield of PSB increased 1.2 times and the cost decreased 19.8 times.

An enhanced broad-host-range vector for Gram-negative bacteria: Avoiding tetracycline phototoxicity during the growth of photosynthetic bacteria

A mobilizable, broad-host-range (bhr) plasmid was derived from the widely used IncP1 vector pRK415. The new vector, pRKD418, contains an additional resistance gene and an enlarged multiple cloning site (MCS) region. The optimal growth of pRK415-containing bacteria under photosynthetic conditions generally requires the use of optical filters to protect the selective antibiotic tetracycline (Tc) from photooxidation with the resulting production of toxic photoproducts; pRK415 is not stably maintained in the absence of selective pressure. The addition of a trimethoprim-resistant dihydrofolate reductase-encoding gene provided for optimal photosynthetic growth in the presence of a selective antibiotic without any special apparatus. The presence of an antibiotic marker not found in commonly used cloning vectors in many cases facilitates the subcloning of inserts into the bhr plasmid. The new MCS region provides further cloning flexibility with at least sixteen available restriction sites. Easily constructed derivative plasmids, exemplified by pRKD418KmE, provide a convenient screening procedure for the detection of recombinants during subcloning.