Papers by MIchele Stanley
Journal of Applied Phycology, Mar 23, 2022
iScience, Jul 1, 2021
Summary Large-scale algal oil production requires continuous outputs and a trade-off between grow... more Summary Large-scale algal oil production requires continuous outputs and a trade-off between growth and oil content. Two unrelated marine algae (Nannochloropsis oceanica [CCAP 849/10] and Chlorella vulgaris [CCAP 211/21A]) that showed high oil production under batch culture were studied under controlled semicontinuous cultivation conditions. Three essential attributes maximized oil productivity: (i) downregulation of cell size to maximize light absorption under N limitation; (ii) low nutrient-depletion thresholds to trigger oil induction; (iii) a means of carbohydrate suppression in favor of oil. N. oceanica responded better to input N/P variations and is more suited to continuous oil production. A low N/P ratio was effective in both suppressing carbohydrate and reducing cell size concomitant with oil production. In C. vulgaris, nutrient starvation thresholds for oil were higher and carbohydrate was preferentially induced, which impeded stress-level optimization for oil. These differences, which impact continuous oil production at scale, are driven by species adaptation to specific marine habitats. Video abstract Video abstract
European Journal of Phycology, Feb 20, 2019
Benthic macroalgae must attach firmly to the substrate to prevent being detached and washed away ... more Benthic macroalgae must attach firmly to the substrate to prevent being detached and washed away by water motion. The success of the bioadhesion system can be strongly influenced by surface chemistry and so this should be optimised for large-scale cultivation. This is especially important during the early stage of cultivation when the juveniles have little thigmotactic attachment, which is needed to interlock with surface rugosity. Juvenile sporophytes of Saccharina latissima (Phaeophyceae) were directly applied onto polymer films of varied surface composition to determine how the attachment force of the developing holdfast was influenced by surface chemistry. Eight polymer chemistries were examined: polyamide (PA), polyethylene (PE), polyester (PES), polypropylene (PP), polymethylacrylate (PMA), polyvinylalcohol (PVA), polyvinylchloride (PVC) and thermoplastic polyurethane (TPU). The PP and PE were also examined as three grades: commercial grade with additives, pure polymer, or pure polymer following a corona treatment. Additive inclusion and corona, significantly reduced the water contact angle (P < 0.0001), indicating an increase in the surface free energy available for bioadhesion. After 6 wk, the attachment force was greatest on PVA, PA and PVC (0.19-0.33 N), correlating strongly with the achieved biomass (R 2 = 0.68). Additives and corona treatment improved holdfast attachment force, particularly corona treated PE (0.28 ± 0.08 N: 0 N without corona). Generally, attachment force appeared greatest on chemistries with a contact angle of 60-75°. These results confirm that the bioadhesion of the phaeophyte holdfast is strongly influenced by the surface free energy of the substrate chosen. Through alteration of the additive composition, attachment could be improved to create bespoke cultivation substrates. Corona treatment is highlighted as a very suitable method for improving holdfast attachment force during cultivation.
Scientific Reports, Feb 14, 2019
As algal biotechnology develops, there is an increasing requirement to conserve cultures without ... more As algal biotechnology develops, there is an increasing requirement to conserve cultures without the cost, time and genetic stability implications of conventional serial transfers, including issues regarding potential loss by failure to regrow, contamination on transfer, mix up and/or errors in the documentation on transfer. Furthermore, it is crucial to ensure both viability and functionality are retained by stored stock-cultures. Low temperature storage, ranging from the use of domestic freezers to storage under liquid nitrogen, is widely being used, but the implication to stability and function rarely investigated. We report for the first time, retention of functionality in the maintenance of master stock-cultures of an industrially relevant, lipid-producing alga, under a variety of cryopreservation regimes. Storage in domestic (-15 °C), or conventional -80 °C freezers was suboptimal, with a rapid reduction in viability observed for samples at -15 °C and a >50% loss of viability, within one month, for samples stored at -80 °C. No reduction in viability occurred at -196 °C. Post-thaw culture functional performance was also influenced by the cryopreservation approach employed. Only samples held at -196 °C responded to nitrogen limitation in terms of growth characteristics and biochemical profiles (lipid production and chlorophyll a) comparable to the untreated control, cultured prior to cryopreservation. These results have important implications in microbial biotechnology, especially for those responsible for the conservation of genetic resources.
Algal Research-Biomass Biofuels and Bioproducts, Mar 1, 2017
For the cultivation of the European phaeophyte macroalgae Laminaria digitata and Saccharina latis... more For the cultivation of the European phaeophyte macroalgae Laminaria digitata and Saccharina latissima, meiospores are settled onto twines within a hatchery, where they are grown for several months. The twine used is often a customarily selected synthetic polymer, polyamide or polypropylene. However, little is known about the impacts of this choice on hatchery performance. To test the effect of substrate material, we settled and cultured meiospores from both L. digitata and S. latissima, independently on twelve polymer blocks for 4 mo. They were first grown for 2 mo under laboratory conditions, then a further 2 mo in outdoor tanks. Meiospore settlement varied significantly between polymers by up to 15-fold (p<0.0001) with some species-specific differences also observed (p<0.0001). Tufnol was the least suitable polymer, as formaldehyde leachate reduced settlement and inhibited juvenile growth/development. After 8 wk, all polymers excluding Tufnol, were performing similarly with generally ~1 mm sporophytes present at a density of 1-2•mm -2 , A negative density-dependent effect of sporophyte size and density was observed in both species (p<0.05). At the end of the experiment, two distinct grouping of polymers were identified regarding S. latissima. Those that initially had very high settlement (high density polyethylene, polymethyl methacrylate, polyoxymethylene copolymer/homopolymer and polytetrafluoroethylene) had the lowest final mean lengths, % cover and biomass (<0.2g wet weight•block -1 ) at the end of the experiment. Conversely many of the polymers with the lowest initial settlement (polyamide, polycarbonate, medium density polyethylene and polyvinylchloride) had the highest final mean lengths, % cover and biomass (1.7-4.9 g wet weight•block -1 ). This reversal of fortunes is discussed regarding discriminatory meiospore settlement, differences in apparent adhesion strength of the seaweed holdfast and the transition of the growing sporophytes from a viscous force dominated boundary layer environment to a turbulent dominated environment with increasing drag as the sporophyte grows.
Journal of Applied Phycology, Sep 26, 2022
Cultivation of Osmundea pinnati da (Hudson) Stackhouse in asks and/or tanks has yet to be develop... more Cultivation of Osmundea pinnati da (Hudson) Stackhouse in asks and/or tanks has yet to be developed beyond the lab scale. However, establishment of a methodology for the supply of this red seaweed has great potential, considering that it can be exploited either as food or as a source of biologically active compounds with potential nutraceutical, pharmaceutical and cosmetic applications. This study investigates the possibility of growing O. pinnati da in the Algem® photo bioreactor (PBR) system, normally utilised for microalgae cultivation, and examines the antioxidant content of the biomass. The cultures were incubated in the Algem® PBRs under a set of environmental parameters established in a previous seasonality study at a single location in the west of Scotland. The growth of the cultures in the PBR was monitored, the biomass assessed for antioxidant content, and results compared with seasonal samples, to assess how the PBR system affects the biochemistry of the species. Analyses centred on antioxidant activity and included Total Phenolic Content (TPC) and Ferric Iron Reducing Antioxidant Power (FRAP). A signi cant increase in the antioxidant content, two to ve-time higher compared to wild samples, was achieved by cultivating the biomass in the PBR. This study highlights that the production of antioxidant compounds in O. pinnati da can be improved by increasing photoperiod and light intensity and manipulating the wavelength. This information provides important insights into how cultivation conditions for this species can be tailored to increase production and improve the composition of the nal product.
Journal of Environmental Management, Jul 1, 2021
Macroalgal biosorption has shown promise for the removal of metal ions from wastewaters, whose pr... more Macroalgal biosorption has shown promise for the removal of metal ions from wastewaters, whose presence can pose a threat to the aquatic environment. There is a wealth of literature published on macroalgal biosorption, the common thread being that the biosorbent material was collected from the field, under undefined conditions. These studies offer little insight into the impact of prior cultivation or biomass production practices upon the biosorbent material, its adsorptive physicochemical properties and its subsequent capacity for metal removal. The present study sought to investigate the influence of changes in macroalgal cultivation, specifically nutrient regime, upon biomass properties and the resultant adsorption performance. The macroalga Cladophora parriaudii was cultivated under six different nutrient regimes; 2:1 and 12:1 N:P molar ratios, with nitrogen supplied either as ammonium (NH4 + ), nitrate (NO3 -), or urea (CO(NH2)2). These nutrient regimes were designed to produce biomass of varying biochemical and cell surface profiles. After cultivation, the biomass was rinsed, dried, biochemically analysed and then used for the removal of four individual metals from solution. Metal removal varied considerably between treatments and across initial metal concentrations, with removal values of 46-85%, 9-80%, 8-71%, and 49-94% achieved for Al, Cu, Mn, and Pb, respectively, with initial metal concentrations varying between 0-150 mg L -1 . The observed variation in metal removal can only be attributed to differences in biochemistry and cell surface properties of the biosorbent induced by nutrient regime, as all other variables were constant. This study demonstrates that prior cultivation conditions influence the biochemistry of a biosorbent material, namely macroalgae Cladophora parriaudii, which has an impact upon metal removal. This aspect should be given due consideration for future biosorption research and when reviewing already published literature.
Journal of Applied Phycology, 2021
The metabolic profile of seaweeds can fluctuate depending on environmental factors and biotic/abi... more The metabolic profile of seaweeds can fluctuate depending on environmental factors and biotic/abiotic stresses. Osmundea pinnatifida is a red alga, known as Pepper Dulse in the UK, harvested from the wild and sold as seasoning due to its unique peppery taste. This paper highlights the seasonal variation in the compositional profile of biomass harvested from a single location over 12 months, linking this to variation in flavour. Hydrophilic interaction chromatography with tandem mass spectrometry (HILIC-PDA-MS) analysis putatively identified 33 major components. Some of these have been noted in other Osmundea species (e.g. chilenones) or identified as osmoregulators in other seaweeds (e.g. mycosporines, betaines or sugar-glycerol components). Central metabolites were identified (e.g. amino or organic acids), as were others not previously recorded in seaweeds. The metabolites varied in abundance across the seasons and could be allocated into five trends those that decreased in summer/increased in winter, increased or decreased in autumn, increased in summer/decreased in winter, those which did not vary, and those with no apparent pattern. Components were identified that increased in abundance in winter when the flavour of Pepper Dulse is more potent. Many of these components were extracted under aqueous conditions that replicate those in the mouth and could therefore contribute to the flavour of this seaweed. This information increases our knowledge about the biochemical composition and its seasonal variation of Osmundea pinnatifida providing insights on compounds that might be related to its taste, thus providing information relevant to future commercialization and harvest management of this species.
The emerging concept of the Blue Economy is being pioneered by Small Island Developing States (SI... more The emerging concept of the Blue Economy is being pioneered by Small Island Developing States (SIDS) as a mechanism for sustainable development of their ocean-based economies. SIDS share common drivers of socioeconomic progress, energy and food security as well as common realities with regard to the adverse impacts of climate change. An integrated and holistic approach is essential to enable growth and innovation in multiple maritime sectors within a Blue Economy, while fully accounting for the social, ecological and economic consequences. Challenges faced in implementing the Blue Economy are complex, multi-faceted and interdisciplinary, and development and application of new knowledge, tools and processes is needed to enable SIDS to maximise available opportunities while effectively accounting for risks. This article lays out a pathway for the development of knowledge management, as a key facet of Blue Economy realisation. To support SIDS in progressing towards coherence between po...
Biochemical Society Transactions, 1995
Mycological Research, 1998
A series of comparative physiological and morphological analyses are described for eighteen Dendr... more A series of comparative physiological and morphological analyses are described for eighteen Dendryphiella isolates. Conidial characteristics of ten isolates showed relatively little variation as a result of different incubation conditions. Isolates were markedly tolerant to NaCl and KCl, although some variation between isolates was noted. A variety of nitrogen compounds could be utilized by most isolates although some grew poorly with certain nitrogen sources. Most isolates showed a wide pH growth range, particularly at alkaline values, and broad temperature growth profiles. The relevance of these physiological characteristics to the survival and fitness of Dendryphiella species in the marine environment is discussed.
Fungal Genetics Reports, Jul 25, 1995
Relatively few fungal genera possess the extensive collections of mutants or reliable transformat... more Relatively few fungal genera possess the extensive collections of mutants or reliable transformation systems that are found in favoured species such as Aspergillus nidulans, Saccharomyces cerevisiae or Neurospora crassa. Consequently, heterologous gene cloning protocols that circumvent the requirement for mutant construction or the development of transformation vectors in a previously uncharacterized species, are attractive. Lambda vectors probably provide the most versatile group of cloning vehicles but, with some exceptions (Pall and Brunelli 1994 Fungal Genet. Newsl. 41 41:63-65 ), they do not carry selectable markers for fungal transformation. Cooley et al (1990 Mycol. Res. 94 94:145-151) nevertheless demonstrated that lambda molecules could be cotransformed effectively into Septoria nodorum along with a conventional vector carrying a selectable marker. Here, we describe an extension of that protocol demonstrating that such cotransformed molecules can be rescued efficiently from Aspergillus nidulans as a host. Lambda genomic DNA libraries of other fungi may thus be screened by complementation of A. nidulans mutants. Additionally, the protocol offers a second method of gene bank screening via conventional plaque hybridization, so exploiting the large cloning capacity of lambda replacement vectors. Recently, we have cloned DNA capable of complementing the A. nidulans salt sensitivity mutation sltA1, (Spathas 1978 Aspergillus Newslett. 14 14:28), from the marine hyphomycete Dendryphiella salina, using this cotransformation approach.
Polymers
Poly-γ-glutamic acid (γ-PGA) is a bio-derived water-soluble, edible, non-immunogenic nylon-like p... more Poly-γ-glutamic acid (γ-PGA) is a bio-derived water-soluble, edible, non-immunogenic nylon-like polymer with the biochemical characteristics of a polypeptide. This Bacillus-derived material has great potential for a wide range of applications, from bioremediation to tunable drug delivery systems. In the context of oral care, γ-PGA holds great promise in enamel demineralisation prevention. The salivary protein statherin has previously been shown to protect tooth enamel from acid dissolution and act as a reservoir for free calcium ions within oral cavities. Its superb enamel-binding capacity is attributed to the L-glutamic acid residues of this 5380 Da protein. In this study, γ-PGA was successfully synthesised from Bacillus subtilis natto cultivated on supplemented algae media and standard commercial media. The polymers obtained were tested for their potential to inhibit demineralisation of hydroxyapatite (HAp) when exposed to caries simulating acidic conditions. Formulations presenti...
Biomass Conversion and Biorefinery
Biorefinery approaches offer the potential to improve the economics of the microalgae industry by... more Biorefinery approaches offer the potential to improve the economics of the microalgae industry by producing multiple products from a single source of biomass. Chromochloris zofingiensis shows great promise for biorefinery due to high biomass productivity and a diverse range of products including secondary carotenoids, predominantly astaxanthin; lipids such as TAGs; carbohydrates including starch; and proteins and essential amino acids. Whilst this species has been demonstrated to accumulate multiple products, the development of an integrated downstream process to obtain these is lacking. The objective of this review paper is to assess the research that has taken place and to identify the steps that must be taken to establish a biorefinery approach for C. zofingiensis. In particular, the reasons why C. zofingiensis is a promising species to target for biorefinery are discussed in terms of cellular structure, potential products, and means to accumulate desirable components via the alt...
Presentation of carbohydrate analysis of seaweed in the biorefinery to chemicals and fuel context... more Presentation of carbohydrate analysis of seaweed in the biorefinery to chemicals and fuel context, presented at the International Seaweed Symposium 2016, Copenhagen, Denmark, 19-24 June 2016.
Journal of Applied Phycology, 2012
The phenotypic and phylogenetic diversity of micro-algae capable of accumulating triacylglycerols... more The phenotypic and phylogenetic diversity of micro-algae capable of accumulating triacylglycerols provides a challenge for the accurate determination of biotechnological potential. High-yielding strains are needed to improve economic viability and their compositional information is required for optimizing biodiesel properties. To facilitate a high-throughput screening programme, a very rapid direct-derivatization procedure capable of extracting lyophilized material for GC analysis was compared with a scaled-down Folch-based method. This was carried out on ten micro-algal strains from 6 phyla where the more rapid direct-derivatization approach was found to provide a more reliable measure of yield. The modified Folch-based procedure was found to substantially underestimate oil yield in one Chlorella species (P<0.01). In terms of fatty acid composition however, the Folch procedure proved to be slightly better in recovering polyunsaturated fatty acids, in six out of the ten strains. Therefore, direct-derivatization is recommended for rapid determination of yields in screening approaches but can provide slightly less compositional accuracy than solvent-based extraction methods.
Mycological Research, 2002
We report the cloning and sequencing of a DNA fragment encoding a putative C # H # zinc finger pr... more We report the cloning and sequencing of a DNA fragment encoding a putative C # H # zinc finger protein from Aspergillus nidulans. The gene was isolated by complementation cloning of a salt sensitive phenotype of the A. nidulans sltA1 mutant. A 3n8 kb PstI fragment that restored wild type salt tolerance contained one large open reading frame of 2202 bp. The predicted protein (StzA) from this reading frame comprises 698 amino acids and has three Zinc fingers along with a putative transcriptional activation domain rich in acidic amino acids. The corresponding sequence from a sltA1 mutant contains a premature STOP codon resulting in loss of the putative transcriptional activator in the C-terminal region. The Zinc fingers show conserved motifs with a number of transcription factors including CreA from A. nidulans and the human Wilm's tumour susceptibility protein WT-1.
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Papers by MIchele Stanley