Nicholas A. Paul

Bio: Nicholas A. Paul is an academic researcher from University of the Sunshine Coast. The author has contributed to research in topics: Biomass & Oedogonium. The author has an hindex of 38, co-authored 115 publications receiving 3747 citations. Previous affiliations of Nicholas A. Paul include University of New South Wales & Commonwealth Scientific and Industrial Research Organisation.

The protein content of seaweeds: a universal nitrogen-to-protein conversion factor of five

Abstract: A global drive to source additional and sustainable biomass for the production of protein has resulted in a renewed interest in the protein content of seaweeds. However, to determine accurately the potential of seaweeds as a source of protein requires reliable quantitative methods. This article systematically analysed the literature to assess the approaches and methods of protein determination and to provide an evidence-based conversion factor for nitrogen to protein that is specific to seaweeds. Almost 95 % of studies on seaweeds determined protein either by direct extraction procedures (42 % of all studies) or by applying an indirect nitrogen-to-protein conversion factor of 6.25 (52 % of all studies), with the latter as the most widely used method in the last 6 years. Meta-analysis of the true protein content, defined as the sum of the proteomic amino acids, demonstrated that direct extraction procedures underestimated protein content by 33 %, while the most commonly used indirect nitrogen-to-protein conversion factor of 6.25 over-estimated protein content by 43 %. We therefore determined whether a single nitrogen-to-protein conversion factor could be used for seaweeds and evaluated how robust this would be by analysing the variation in this factor for 103 species across 44 studies that span three phyla, multiple geographic regions and a range of nitrogen contents. An overall median nitrogen-to-protein conversion factor of 4.97 was established and an overall mean nitrogen-to-protein conversion factor of 4.76. We propose that the overall median value of 5 be used as the most accurate universal seaweed nitrogen-to-protein (SNP) conversion factor.

Chemical defence against bacteria in the red alga Asparagopsis armata: linking structure with function

Abstract: Although numerous algal products have antimicrobial activity, limited knowledge of metabolite localisation and presentation in algae has meant that ecological roles of algal natural products are not well understood. In this study, extracts of Asparagopsis armata had antibacterial activity against marine (Vibrio spp.) and biomedical (Escherichia coli, Pseudomonas aeruginosa and Staphylococcus spp.) strains. The major natural products in both life-history stages of A. armata (as determined by gas chromatography-mass spectrometry analysis (GC-MS)) were bromoform (0.58 to 4.3% of dry weight (DW)) and dibromoacetic acid (DBA) (0.02 to 2.6% DW), and each compound was active against these same bacteria. To resolve whether this antibiotic activity was ecologically rele- vant, we examined the localisation of metabolites in the specialised cells of A. armata and observed a delivery mechanism for the release of metabolites to the surface. Bromoform and DBA were sub- sequently quantified in the surrounding medium of laboratory cultures, establishing their release from the alga. In a novel ecological test of algal natural products, halogenated metabolites in A. armata were manipulated by omitting bromine from an artificial seawater medium. Significantly higher densities of epiphytic bacteria occurred on algae that no longer produced halogenated metabolites. Both bromoform and DBA were more active against bacteria isolated from algae lacking brominated metabolites than algae producing normal amounts of these compounds. Taken together, these results indicate that halogenated metabolites of A. armata may be important in reducing epiphytic bacterial densities.

Total lipid and fatty acid composition of seaweeds for the selection of species for oil-based biofuel and bioproducts.

Abstract: We investigated the potential of seaweeds as feedstock for oil-based products, and our results support macroalgae (seaweeds) as a biomass source for oil-based bioproducts including biodiesel. Not only do several seaweeds have high total lipid content above 10% dry weight, but in the brown alga Spatoglossum macrodontum 50% of these lipids are in the form of extractable fatty acids. S. macrodontum had the highest fatty acid content (57.40 mg g−1 dw) and a fatty acid profile rich in saturated fatty acids with a high content of C18:1, which is suitable as a biofuel feedstock. Similarly, the green seaweed Derbesia tenuissima has high levels of fatty acids (39.58 mg g−1 dw), however, with a high proportion of PUFA (n-3) (31% of total lipid) which are suitable as nutraceuticals or fish oil replacements. Across all species of algae the critical parameter of fatty acid content (measured as fatty acid methyl esters, FAME) was positively correlated (R2 = 0.67) with total lipid content. However, the proportion of fatty acids to total lipid decreased markedly with total lipid content, generally between 30% and 50%, making it an inaccurate measure of the potential to identify seaweeds suitable for oil-based bioproducts. Finally, we quantified within species variation of fatty acids across locations and sampling periods supporting either environmental effects on quantitative fatty acid profiles, or genotypes with specific quantitative fatty acid profiles, thereby opening the possibility to optimize the fatty acid content and quality for oil production through specific culture conditions and selective breeding.

Effects of marine and freshwater macroalgae on in vitro total gas and methane production.

Abstract: This study aimed to evaluate the effects of twenty species of tropical macroalgae on in vitro fermentation parameters, total gas production (TGP) and methane (CH4) production when incubated in rumen fluid from cattle fed a low quality roughage diet. Primary biochemical parameters of macroalgae were characterized and included proximate, elemental, and fatty acid (FAME) analysis. Macroalgae and the control, decorticated cottonseed meal (DCS), were incubated in vitro for 72 h, where gas production was continuously monitored. Post-fermentation parameters, including CH4 production, pH, ammonia, apparent organic matter degradability (OMd), and volatile fatty acid (VFA) concentrations were measured. All species of macroalgae had lower TGP and CH4 production than DCS. Dictyota and Asparagopsis had the strongest effects, inhibiting TGP by 53.2% and 61.8%, and CH4 production by 92.2% and 98.9% after 72 h, respectively. Both species also resulted in the lowest total VFA concentration, and the highest molar concentration of propionate among all species analysed, indicating that anaerobic fermentation was affected. Overall, there were no strong relationships between TGP or CH4 production and the >70 biochemical parameters analysed. However, zinc concentrations >0.10 g.kg−1 may potentially interact with other biochemical components to influence TGP and CH4 production. The lack of relationship between the primary biochemistry of species and gas parameters suggests that significant decreases in TGP and CH4 production are associated with secondary metabolites produced by effective macroalgae. The most effective species, Asparagopsis, offers the most promising alternative for mitigation of enteric CH4 emissions.

A review of biochar as a low-cost adsorbent for aqueous heavy metal removal

Abstract: As a low-cost adsorbent, biochar can be used as a low-cost adsorbent for wastewater treatment, particularly with respect to treating heavy metals in wastewater. A number of studies have demonstrated effective removal of heavy metals from aqueous solutions by biochar and, in some cases, proven the superiority of biochars to activated carbons. Among several factors affecting the sorption ability of biochars, feedstock materials play a significant role. This review incorporates existing literature to understand the overall sorption behavior of heavy metals on biochar adsorbents. Depending on the biochar type, heavy metal can be removed by different mechanisms such as complexation, physical sorption, precipitation and electrostatic interactions. Mathematical sorption models can be used to understand the efficiency of biochar at removing heavy metals, and promote the application of biochar technology in water treatment.

Algae as nutritional and functional food sources: revisiting our understanding

Abstract: Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.