J. Grant Burgess

Glutamate production from CO2 by Marine Cyanobacterium Synechococcus sp. - Using a Novel Biosolar Reactor Employing Light-Diffusing Optical Fibers

ABstractA photobioreactor was constructed in the form of a Perspex column 900 mm tall with an internal diameter of 70 mm. The reactor volume was 1.8 L and the light source consisted of a metal-halide lamp to reproduce sunlight. Light was distributed through the culture using a new type of optical fiber that diffuses light out through its surface, perpendicular to the fiber axis. A cluster of 661 light-diffusing optical fibers (LDOFs) pass from the light source through the reactor column (60-cm culture depth) and are connected to a mirror at the top of the reactor. This biosolar reactor has been used for the production of glutamate from CO2 by the marine cyanobacterium Synechococcus sp. NKBG040607. We present here details of the construction of the biosolar reactor and characterization of its properties. The effect of light intensity on glutamate production was measured. Carbon dioxide-to-glutamate conversion ratios were determined at different cell densities: the maximum conversion ratio (28%) was achieved at a cell density of 3x108 cells/mL. A comparison of glutamate production using the LDOF biosolar reactor described here with production by batch culture using free or immobilized cells showed that use of an optical-fiber biosolar reactor increased glutamate-production efficiency 6.75-fold. We conclude that as a result of its high surface-to-volume ratio (692/m) increased photoproduction of useful compounds may be achieved. Such a system is generally applicable to all aspects of photobiotechnology.

An ultraviolet (UV-A) absorbing biopterin glucoside from the marine planktonic cyanobacterium Oscillatoria sp.

We have investigated the physiological response of marine planktonic cyanobacteria to UV-A (320–390 nm) irradiation. Here, we report the isolation of a UV-A absorbing pigment from a UV-A resistant strain of Oscillatoria. This pigment has been purified, and its structure determined to be biopterin glucoside (BG), a compound chemically related to the pteridine pigments found in butterfly wings. A UV-A sensitive isolate did not produce significant levels of this chromophore. UV-A radiation was very effective in eliciting synthesis of BG. In addition, increased UV-A radiation, increased intracellular levels of BG. These data suggest that BG may protect the cyanobacterium from adverse effects of UV-A radiation.

CO2 removal by high-density culture of a marine cyanobacterium synechococcus sp. using an improved photobioreactor employing light-diffusing optical fibers

A light diffusing optical fiber (LDOF) photobioreactor with an improved gas input system has been used for the high-density culture of a marine cyanobacterium Synechococcus sp. Optimum conditions for CO2 removal and biomass production were investigated. Maximum CO2 removal of 4.44 g/L/d was achieved using an initial cell concentration of 6.8 g/L. The biomass yield was 0.97 g/L for a 12-culture time. Continuous cultures, in which medium was filtered using a ceramic membrane module, showed enhanced growth, with a final cell concentration of 11.2 g/L. These results demonstrate the potential of LDOF photobioreactor units for CO2 removal and biomass production using marine cyanobacteria.

An optical fibre photobioreactor for enhanced production of the marine unicellular alga Isochrysis aff. galbana T-Iso (UTEX LB 2307) rich in docosahexaenoic acid

We have screened six species of marine microalga for their ability to produce the important dietary lipid docosahexaenoic acid (DHA). Isochrysis aff. galbana T-Iso (UTEX LB 2307), which produced DHA in the highest quantities (5.4 mg-g−1), was grown in a new type of closed photobioreactor in which efficient light distribution was achieved using light-diffusing optical fibres. The optimal temperature and light intensity for DHA production were determined and a maximal DHA production of 4.3 mg-l was achieved, twofold greater than that obtained using conventional culture methods. In addition, the DHA content could be enhanced by low temperature or dark incubation of the culture after growth.

Sulfated exopolysaccharide production by the halophilic cyanobacterium Aphanocapsa halophytia

Aphanocapsa halophytia MN-11 isolated from a hypersaline environment was found to produce large quantities of exopolysaccharide. We describe here production of exopolysaccharide and the characterization of its properties. The effects of medium composition, particularly NaCl concentration, were tested. Maximum exopolysaccharide production was obtained with nitrogen and phosphorus concentrations in the medium exceeding 100 and 40 mg · L-1 respectively. In addition, when 30 g · L-1 NaCl was added to the medium, exopolysaccharide could be recovered from the medium supernatant. Exopolysaccharide from this strain was made up of at least six mono-oses and did not contain uronic derivatives or osamines. Proteins represented about 10% of total weight and, interestingly, 12% (wt/wt) sulfated residues, which is unusual for photosynthetic prokaryotes.

Conjugative gene transfer in marine cyanobacteria: Synechococcus sp., Synechocystis sp. and Pseudanabaena sp.

SummaryVersatility of gene transfer by transconjugation in marine cyanobacteria was demonstrated. In this study, seven different marine cyanobacteria were used as recipient cells. First, transconjugation was carried out using the mobilizable transposon (Tn5) carrying plasmid pSUP1021. Transconjugants were observed in all marine cyanobacteria tested. Second, the broad-host-range vector pKT230 (IncQ) was tested for transconjugation. pKT230 has been successfully transferred in a marine cyanobacterium Synechococcus sp. NKBG15041C, and replicated as an autonomous replicon without alteration in the restriction enzyme pattern. A maximum transfer efficiency of 5.2 × 10−4 transconjugants/recipient cell was observed, when mating was performed on agar plates containing low salinity (0.015 m NaCl) medium. This is the first study to demonstrate gene transfer in marine cyanobacteria via transconjugation.

Effect of ultraviolet-A (UV-A) light on growth, photosynthetic activity and production of biopterin glucoside by the marine UV-A resistant cyanobacterium Oscillatoria sp.

We have isolated a marine planktonic cyanobacterium Oscillatoria sp. NKBG 091600 which is resistant to ultraviolet-A (UV-A) irradiation. In response to UV-A irradiation this cyanobacterium produces high levels of a UV-A absorbing compound which was identified previously as biopterin glucoside. Here, we have investigated the effect of UV-A light intensity on growth, biopterin glucoside production and photosynthetic activity. Oscillatoria sp. NKBG 091600 could grow at UV-A intensities of up to 800 microW/cm2 and at 300 microW/cm2 could grow as well as in the absence of UV-A irradiation. In addition, pre-culture of cells with UV-A protected cells from UV-A induced inhibition of photosynthetic activity. Detection of biopterin glucoside levels in irradiated cells by HPLC demonstrated that after 10 h there was a rapid increase in biopterin glucoside content. This increase was dependent on the intensity on the intensity of the UV-A irradiation.

Cloning, sequencing and expressing the carotenoid biosynthesis genes, lycopene cyclase and phytoene desaturase, from the aerobic photosynthetic bacterium Erythrobacter longus sp. strain Och101 in Escherichia coli

Two genes which encode the enzymes lycopene cyclase and phytoene desaturase in the aerobic photosynthetic bacterium Erythrobacter longus sp. strain Och101 have been cloned and sequenced. The gene for lycopene cyclase, designated crtY, was expressed in a strain of Escherichia coli which contained the crtE, B, I and Z genes encoding geranylgeranyl pyrophosphate synthase, phytoene synthase, phytoene desaturase, and beta-carotene hydroxylase, respectively. As a result, zeaxanthin production was observed in E. coli transformants. In addition, expression of the E. longus gene crtI for phytoene desaturase in E. coli containing crtE and B resulted in the accumulation of lycopene in transformants. Zeaxanthin and lycopene were also determined by mass spectrum. Nucleotide sequence similarities between E. longus crtY gene and other microbial lycopene cyclase genes are 40.2% (Erwinia herbicola), 37.4% (Erwinia uredovora) and 22.9% (Synechococcus sp.), and those between phytoene desaturase genes are 50.3% (E. herbicola), 54.7% (E. uredovora) and 39.6% (Rhodobacter capsulatus).

Characterization of iron uptake in the magnetic bacterium Aquaspirillum sp. AMB-1

The aim of this work is to elucidate the iron uptake mechanism in the magnetic bacteriumAquaspirillum sp. AMB-1, which can utilize a wide variety of iron chelates. However, no siderophore could be detected in spent culture. A 400-bp DNA fragment was amplified by polymerase chain reaction (PCR) from the genomic DNA of AMB-1, using primers designed from thesfuC gene ofSerratia marcescens. This gene encodes a nucleotide binding protein in the periplasmic binding protein (PBP) dependent iron transport system. The amplified fragment was homologous with the conserved sequence ofsfuC. Our results suggest that a nucleotide binding protein mediated iron transport system similar to that observed inSerratia marcescens is present inAquaspirillum sp. AMB-1.

Development of a rapid isolation procedure for coccolith ultrafine particles produced by coccolithophorid algae

A rapid procedure for effective purification of large quantities of coccolith ultrafine particles from marine algae is reported. Coccoliths are detached from cells by optimized sonication in the presence of 50 mM NaHCO3. Contaminating cell debris is then removed from coccoliths by cycles of washing and floatation. Coccolith particles were purified fromEmiliania huxleyi andPleurochrysis carterae. The surface area of these particles is three to five times greater than synthetic calcite particles. Glucose oxidase and uricase have been immobilized onto purified coccolith ultrafine particles to illustrate their potential as a support material for biotechnological application.