Co-Producing Phycocyanin and Bioplastic in Arthrospira platensis Using Carbon-Rich Wastewater.

Microalgae can treat waste streams containing elevated levels of organic carbon and nitrogen. This process can be economically attractive if high value products are created simultaneously from the relatively low-cost waste stream. Co-production of two high value microalgal products, phycocyanin and polyhydroxybutyrate (PHB), was investigated using non-axenic Arthrospira platensis MUR126 and supplemental organic carbon (acetate, oxalate, glycerol and combinations). All supplemented cultures had higher biomass yield (g/L) than photoautotrophic control. All cultures produced PHB (3.6-7.8% w/w), except the control and those fed oxalate. Supplemented cultures showed a two to three-fold increase in phycocyanin content over the eight-day cultivation. Results indicate co-production of phycocyanin and PHB is possible in A. platensis, using mixed-waste organic carbon. However, supplementation resulted in growth of extremophile bacteria, particularly in cultures fed glycerol, and this had a negative impact on culture health. Refinement of the carbon dosing rate is required to minimise impacts of native bacterial contamination.

The Genome of the Acid Soil-Adapted Strain Rhizobium favelukesii OR191 Encodes Determinants for Effective Symbiotic Interaction With Both an Inverted Repeat Lacking Clade and a Phaseoloid Legume Host.

Although Medicago sativa forms highly effective symbioses with the comparatively acid-sensitive genus Ensifer, its introduction into acid soils appears to have selected for symbiotic interactions with acid-tolerant R. favelukesii strains. Rhizobium favelukesii has the unusual ability of being able to nodulate and fix nitrogen, albeit sub-optimally, not only with M. sativa but also with the promiscuous host Phaseolus vulgaris. Here we describe the genome of R. favelukesii OR191 and genomic features important for the symbiotic interaction with both of these hosts. The OR191 draft genome contained acid adaptation loci, including the highly acid-inducible lpiA/acvB operon and olsC, required for production of lysine- and ornithine-containing membrane lipids, respectively. The olsC gene was also present in other acid-tolerant Rhizobium strains but absent from the more acid-sensitive Ensifer microsymbionts. The OR191 symbiotic genes were in general more closely related to those found in Medicago microsymbionts. OR191 contained the nodA, nodEF, nodHPQ, and nodL genes for synthesis of polyunsaturated, sulfated and acetylated Nod factors that are important for symbiosis with Medicago, but contained a truncated nodG, which may decrease nodulation efficiency with M. sativa. OR191 contained an E. meliloti type BacA, which has been shown to specifically protect Ensifer microsymbionts from Medicago nodule-specific cysteine-rich peptides. The nitrogen fixation genes nifQWZS were present in OR191 and P. vulgaris microsymbionts but absent from E. meliloti-Medicago microsymbionts. The ability of OR191 to nodulate and fix nitrogen symbiotically with P. vulgaris indicates that this host has less stringent requirements for nodulation than M. sativa but may need rhizobial strains that possess nifQWZS for N2-fixation to occur. OR191 possessed the exo genes required for the biosynthesis of succinoglycan, which is required for the Ensifer-Medicago symbiosis. However, 1H-NMR spectra revealed that, in the conditions tested, OR191 exopolysaccharide did not contain a succinyl substituent but instead contained a 3-hydroxybutyrate moiety, which may affect its symbiotic performance with Medicago hosts. These findings provide a foundation for the genetic basis of nodulation requirements and symbiotic effectiveness with different hosts.

Zn Metal Atom Doping on the Surface Plane of One-Dimesional NiMoO4 Nanorods with Improved Redox Chemistry.

The effect of zinc (Zn) doping and defect formation on the surface of nickel molybdate (NiMoO4) structures with varying Zn content has been studied to produce one-dimensional electrodes and catalysts for electrochemical energy storage and ethanol oxidation, respectively. Zn-doped nickel molybdate (Ni1-xZnxMoO4, where x = 0.1, 0.2, 0.4, and 0.6) nanorods were synthesized by a simple wet chemical route. The optimal amount of Zn is found to be around 0.25 above which the NiMoO4 becomes unstable, resulting in poor electrochemical activity. This result agrees with our density functional theory calculations in which the thermodynamic stability reveals that Ni1-xZnxMoO4 crystallized in the ß-NiMoO4 phase and is found to be stable for x≤0.25. Analytical techniques show direct evidence of the presence of Zn in the NiMoO4 nanorods, which subtly alter the electrocatalytic activity. Compared with pristine NiMoO4, Zn-doped NiMoO4 with the optimized Zn content was tested as an electrode for an asymmetric supercapacitor and demonstrated an enhanced specific capacitance of 122 F g-1 with a high specific energy density of 43 W h kg-1 at a high power density of 384 W kg-1. Our calculations suggest that the good conductivity from Zn doping is attributed to the formation of excess oxygen vacancies and dopants play an important role in enhancing the charge transfer between the surface and OH- ions from the electrolyte. We report electrochemical testing, material characterization, and computational insights and demonstrate that the appropriate amount of Zn in NiMoO4 can improve the storage capacity (∼15%) due to oxygen vacancy interactions.

Outdoor phycocyanin production in a standalone thermally-insulated photobioreactor.

The operation of solar microalgal photobioreactors requires sufficient cooling and heating to maintain reliable high productivity year-round. These operations are energy-intensive and expensive. Growth characteristics and phycocyanin production of Arthrospira platensis were investigated during the austral winter using a thermally-insulated photobioreactor with photovoltaic panel integration for electricity generation. This was compared with a control photobioreactor under a cycle of heating (13-hour night) and thermostat-regulated cooling, and continuously heated raceway pond. Average temperature in the photovoltaic photobioreactor (21.0 ± 0.03 °C) was similar to that in the heated control. Biomass productivity of Arthrospira in the novel photobioreactor was 67% higher than in the raceway pond but significantly lower than the control. Phycocyanin productivity (16.3 ± 1.43 mgg-1d-1 and purity (1.2 ± 0.03) showed no variation between photobioreactors but was significantly lower in the raceway pond. Electrical energy output of the photovoltaic photobioreactor exceeded mixing energy needs by 75%. These results indicate that the novel photobioreactor offers a reliable, energy-efficient platform for large-scale production of high-value chemicals from microalgae.

Contributions of Root WSC during Grain Filling in Wheat under Drought.

As the first organ in plants to sense water-deficit in the soil, roots have important roles for improving crop adaption to water limited environments. Stem water soluble carbohydrates (WSC) are a major carbon source for grain filling under drought conditions. The contributions of root WSC during grain filling under drought has not been revealed. Wheat parental lines of Westonia, Kauz and their derived four double haploid (DH) lines, namely, DH 125, DH 139, DH 307, and DH 338 were used in a field drought experiment with four replications. Through measurements of the root and stem WSC components, and the associated enzyme activities during grain filling, we identified that the levels of root WSC and fructan were one third of the levels in stems. In particular, root glucose and 6-kestose levels were one third of the stem, while the root fructose and bifurcose level were almost half of the stem and sucrose level was two third of the stem. The accumulation and the degradation patterns of root fructan levels were similar to that in the stem, especially under drought. Correlations between root fructan levels and grain assimilation were highly significant, indicating that under terminal drought, root WSC represents a redistributed carbon source for grain filling rather than deep rooting. The significantly higher root sucrose levels under drought suggest that sucrose may act as a signal under drought stress. As compared with stem fructose levels, the earlier increased root fructose levels in DH 307, DH 139, and DH 338 provided agile response to drought stress. Our root results further confirmed that ß-(2-6) linkages predominate in wheat with patterns of 6-kestose being closely correlated with overall fructan patterns. Further research will focus on the roles of 6-FEH during fructan remobilization in stems.

Pycnanthuquinone C, an unusual 6,6,5-tricyclic Geranyltoluquinone from the Western Australian brown alga Cystophora harveyi.

Chemical investigation of the Western Australian marine brown alga Cystophora harveyi resulted in the isolation of the new linearly fused 6,6,5-tricyclic compound pycnanthuquinone C (1), in addition to four previously reported geranyltoluquinol derivatives. Structures were elucidated by interpretation of spectrometric data. Compounds with the same cyclic skeleton as 1 have been reported to be useful drug leads for the treatment of type 2 diabetes, while compounds 4 and 7 are known constituents of Chinese medicinal herbs. A biosynthetic scheme encompassing all of the geranyltoluquinol derivatives isolated from C. harveyi is proposed.

Halogenated cyclic peptides isolated from the sponge Corticium sp.

Fractionation of two Fijian specimens of the sponge Corticium sp. led to the isolation of the known active alkaloid steroid plakinamine A and two new halogenated cyclic peptides, corticiamide A (1) and cyclocinamide B (2). Structural elucidation of 1 and 2 was achieved by an extensive combination of high-field NMR and HRFT MS/MS experiments, and the absolute stereochemistry of 2 was determined by acid hydrolysis and Marfey's analysis. Corticiamide A (1) and cyclocinamide B (2) represent the first peptides to be described from the genus Corticium.

Tetraprenyltoluquinols from the brown alga Cystophora fibrosa.

Six cyclised tetraprenyltoluquinols and five stereoisomers with the previously reported amentol skeleton have been isolated from the lipophilic extract of the South African brown alga Cystophora fibrosa. Structures and relative stereochemistry were determined using spectrometric techniques, particularly 1D and 2D NMR, and molecular modelling experiments. The compounds isolated appear to be enantiomeric to compounds with the same skeleton isolated from brown algae of the genus Cystoseira collected in northern Africa and the Mediterranean Sea. The isolation of tetraprenyltoluquinols with the amentol skeleton from this alga suggests that C. fibrosa should be moved from the genus Cystophora into the Cystoseira.