Andrew J. Poole

Environmentally Sustainable Fibers from Regenerated Protein

Concerns for the environment and consumer demand are driving research into environmentally friendly fibers as replacements for part of the 38 million tonnes of synthetic fiber produced annually. While much current research focuses on cellulosic fibers, we highlight that protein fibers regenerated from waste or byproduct sources should also be considered. Feather keratin and wheat gluten may both be suitable. They are annually renewable, commercially abundant, of consistent quality, and have guaranteed supply. They contain useful amino acids for fiber making, with interchain cross-linking possible via cysteine residues or through the metal-catalyzed photocrosslinking of tyrosine residues. Previous commercially produced fibers suffered from poor wet strength. Contemporary nanoparticle and cross-linking technology has the potential to overcome this, allowing commercial production to resume. This would bring together two existing large production and processing pipelines, agricultural protein production and textile processing, to divert potential waste streams into useful products.

Antisense Suppression of a (+)-δ-Cadinene Synthase Gene in Cotton Prevents the Induction of This Defense Response Gene during Bacterial Blight Infection But Not Its Constitutive Expression

In cotton (Gossypium hirsutum) the enzyme (+)-δ-cadinene synthase (CDNS) catalyzes the first committed step in the biosynthesis of cadinane-type sesquiterpenes, such as gossypol, that provide constitutive and inducible protection against pests and diseases. A cotton cDNA clone encoding CDNS (cdn1-C4) was isolated from developing embryos and functionally characterized. Southern analysis showed that CDNS genes belong to a large multigene family, of which five genomic clones were studied, including three pseudogenes and one gene that may represent another subfamily of CDNS. CDNS expression was shown to be induced in cotton infected with either the bacterial blight or verticillium wilt pathogens. Constructs for the constitutive or seed-specific antisense suppression of cdn1-C4 were introduced into cotton by Agrobacterium-mediated transformation. Gossypol levels were not reduced in the seeds of transformants with either construct, nor was the induction of CDNS expression affected in stems of the constitutive antisense plants infected with Verticillium dahliae Kleb. However, the induction of CDNS mRNA and protein in response to bacterial blight infection of cotyledons was completely blocked in the constitutive antisense plants. These results suggest that cdn1-C4 may be involved specifically in the bacterial blight response and that the CDNS multigene family comprises a complex set of genes differing in their temporal and spatial regulation and responsible for different branches of the cotton sesquiterpene pathway.

Using textured PDMS to prevent settlement and enhance release of marine fouling organisms

The antifouling efficacy of a series of 18 textured (0.2–1000 μm) and non-textured (0 μm) polydimethylsiloxane surfaces with the profiles of round- and square-wave linear grating was tested by recording the settlement of fouling organisms in the laboratory and in the field by monitoring the recruitment of a multi-species fouling community. In laboratory assays, the diatoms Nitzschia closterium and Amphora sp. were deterred by all surface topographies regardless of texture type. Settlement of propagules of Ulva sp. was lower on texture sizes less than the propagule size, and settlement of larvae of Saccostrea glomerata and Bugula neritina was lower on texture sizes closest to, but less than, the sizes of larvae. After a six month field trial, all textured surfaces lost their deterrent effect; however, the foul-release capabilities of textures were still present. High initial attachment was correlated with most fouling remaining after removal trials, indicating that fouling organisms recruited in higher numbers to surfaces upon which they attached most strongly.

Enhancing the settlement and attachment strength of pediveligers of Mytilus galloprovincialis bychanging surface wettability and microtopography

Surface wettability and microtopography can either enhance or deter larval settlement of many sessile marine organisms. This study quantifies the effect of these surface properties on the settlement of pediveligers of Mytilus galloprovincialis, using polymers spanning a range of wettability and microtextured polydimethylsiloxane (PDMS). Furthermore, the adhesion strength of settled pediveligers on microtextured PDMS surfaces was quantified using a flow chamber. Settlement was enhanced at the hydrophilic end of the wettability spectrum, where mean settlement on nylon reached 33.5 ± 13.1%. In contrast, mean settlement on the most hydrophobic polymer (PDMS) was 4.2 ± 3.2%. Microtopography had a much stronger effect compared to wettability, where 400 μm textured PDMS enhanced settlement above 90%. Settlement preferences were also positively correlated to adhesion strength at flow rates of 4 knots, with all initially settled pediveligers on smooth PDMS detaching, while 79.9 ± 5.7% of pediveligers remained on the 400 μm texture.

Grain Development Mutants of Barley ([alpha]-Amylase Production during Grain Maturation and Its Relation to Endogenous Gibberellic Acid Content)

Barley (Hordeum vulgare L. Himalaya) mutants with altered grain morphology were isolated to investigate whether defects in grain development, possibly involving gibberellins (GAs) and abscisic acid, would lead to altered patterns of [alpha]-amylase gene expression. Following treatment with sodium azide, 75 mutants, typically showing grain shriveling, were identified. At grain maturity 15 of the 75 mutants had higher [alpha]-amylase activities in shriveled grains compared with either phenotypically normal grains that developed on the same heterozygous plant or with grains of cv Himalaya. Studies of four of these mutants demonstrated increased levels of both high- and low-isoelectric point [alpha]-amylase isozymes midway through grain development. This category of mutant has been designated pga, for premature grain [alpha]-amylase. One such mutant (M326) showed an endosperm-determined inheritance pattern. When crossed into a (GA-deficient) dwarfing background there was a 10- to 20-fold reduction in [alpha]-amylase activity, suggesting a requirement for GA biosynthesis. Endogenous GAs and abscisic acid were quantified by combined gas chromatography-specific ion monitoring in normal and mutant grains of heterozygous M326 plants during the period of [alpha]-amylase accumulation. Mutant grains had significantly higher (5.8-fold) levels of the bioactive GA1 compared with normal grains but much lower (approximately 10-fold) levels of the 2[beta]-hydroxylated (“inactive”) GAs, typical of developing barley grains (e.g. GA8, GA34, GA48). We propose that a reduced extent of 2[beta]-hydroxylation in the mutant grains results in an increased level of GA1, which is responsible for premature [alpha]-amylase gene expression.

Larval settlement: the role of surface topography for sessile coral reef invertebrates

For sessile marine invertebrates with complex life cycles, habitat choice is directed by the larval phase. Defining which habitat-linked cues are implicated in sessile invertebrate larval settlement has largely concentrated on chemical cues which are thought to signal optimal habitat. There has been less effort establishing physical settlement cues, including the role of surface microtopography. This laboratory based study tested whether surface microtopography alone (without chemical cues) plays an important contributing role in the settlement of larvae of coral reef sessile invertebrates. We measured settlement to tiles, engineered with surface microtopography (holes) that closely matched the sizes (width) of larvae of a range of corals and sponges, in addition to surfaces with holes that were markedly larger than larvae. Larvae from two species of scleractinian corals (Acropora millepora and Ctenactis crassa) and three species of coral reef sponges (Luffariella variabilis, Carteriospongia foliascens and Ircinia sp.,) were used in experiments. L. variabilis, A. millepora and C. crassa showed markedly higher settlement to surface microtopography that closely matched their larval width. C. foliascens and Ircinia sp., showed no specificity to surface microtopography, settling just as often to microtopography as to flat surfaces. The findings of this study question the sole reliance on chemical based larval settlement cues, previously established for some coral and sponge species, and demonstrate that specific physical cues (surface complexity) can also play an important role in larval settlement of coral reef sessile invertebrates.

Enhancing the efficacy of fouling-release coatings against fouling by Mytilus galloprovincialis using nanofillers.

Fouling-release (FR) coatings minimise the adhesion strength of fouling organisms. This study describes improved technologies to control the settlement and adhesion of the important fouling organism Mytilus galloprovincialis by incorporating the nanofillers titanium dioxide (TiO2) and carbon nanotubes (CNTs) in polydimethylsiloxane (PDMS) matrices. The incorporation of TiO2 prevented larval settlement when photoactivated with UV light, even at the lowest concentration of the nanofiller (3.75 wt%). Notably, there was 100% mortality of pediveligers exposed to photoactivated TiO2. However, plantigrades initially settled to photoactivated TiO2, but their adhesion strength was significantly reduced on these surfaces in comparison to blank PDMS. In addition, plantigrades had high mortality after 6 h. In contrast to the enhanced antifouling and FR properties of PDMS incorporating TiO2, the incorporation of CNTs had no effect on the settlement and adhesion of M. galloprovincialis.

Cold spray metal embedment: an innovative antifouling technology

The study demonstrates that embedment of copper particles into thermoplastic polymers (polymers) using cold spray technology is an effective deterrent against fouling organisms. Two polymers, high-density polyethylene (HDPE) and nylon were metallised with copper powder using cold spray technology. After 250 days in the field, Cu-embedded HDPE and copper plate controls were completely free of hard foulers compared to Cu-embedded nylon and polymer controls which were heavily fouled with both soft and hard fouling. Antifouling (AF) success is related to the interaction between the properties of the polymers (elastic modulus and hardness) and the cold spray process which affect particle embedment depth, and subsequently, the release of copper ions as determined by analytical techniques. Embedding metal using cold spray equipment is shown to be an effective AF technology for polymers, in particular those that are difficult to treat with standard AF coatings, with efficacy being a function of the interaction between the cold spray metal and the polymer recipient.

The effects of physical and chemical treatments on Na2S produced feather keratin films

The industrial utilisation of feather keratin as a biopolymer has proven difficult due to the lack of a viable extraction technique and the poor mechanical properties of the regenerated products. Here, pure keratin films were produced from chicken feathers using sodium sulphide as sole extraction reagent in a scheme that allows films to be formed without residual chemicals. In a comparison to other films, those produced using Na2S extraction were found to be superior to other regenerated protein films and were similar to un-oriented commercial polymers. However, there was considerable variation in tensile properties between twenty repetitions of extracting and casting films which was attributed to variations in chain entanglement caused by the drying conditions. Chemical and physical treatments including crosslinking, dehydration and addition of nano-particles were investigated as means to enhance these properties. Significant increases were achieved by soaking films in isopropyl alcohol or weak acid (13 to 50% increases) or by formaldehyde or glutaraldehyde crosslinking (24 to 40% increases). The wide range of values across the pure keratin films indicates that the best route to further strength improvement may be from optimising self-assembly via controlling drying conditions, rather than from chemical treatment.

Optimising settlement assays of pediveligers and plantigrades of Mytilus galloprovincialis

The mussel Mytilus galloprovincialis is a common aquaculture species, and also a major fouling organism that has negative economic impacts. There are no standard assay conditions for this important species and therefore, this study quantified the effect of key factors on the settlement of pediveligers and plantigrades. Density dependent settlement did not occur for either pediveligers or plantigrades. Settlement increased in drop assays in a 12 h light:12 h dark cycle, while bottom shade had no effect of any magnitude. In addition, settlement was significantly enhanced by storing pediveligers for between 4 and 24 days at 4°C. Overall, these data provide the template to optimise and standardise static laboratory settlement assays for mussels in order to develop materials that either enhance settlement for the aquaculture industry, or deter settlement for antifouling applications. Furthermore, simple mechanisms such as storage at 4°C can enhance settlement beyond current methods used in aquaculture hatcheries.