The giant kelp (Macrocystis pyrifera (Linnaeus) C. Agardh 1820) is a habitat-forming brown seaweed in temperate systems with an unexplored potential as a source of seaweed bioproducts. This study used M. pyrifera sporophytes sourced in Tasmania, Australia, to investigate the effect of photoperiod and temperature on growth rates and the nutritional characteristics of the resulting juvenile biomass. Four cultivation treatments combined growth temperatures of 12 °C, 15 °C, 18 °C with light:dark (L:D) of 12:12 and 16:8 (L:D) photoperiods, (12 °C – (12:12); 12 °C – (16:8); 15 °C – (12:12); 18 °C – (12:12) to investigate their effect on the number and size of sporophytes, biomass accumulation and nutritional composition. After 60 days of cultivation the 12 °C – (12:12) treatment had the greatest number of juvenile sporophytes, and the greatest biomass of 14 ± 1.3 g dry weight (DW). The lowest biomass of 1 g DW, was obtained from the 18 °C – (12:12) treatment. The protein content across all treatments ranged from 16-22.48% DW, with the 12 °C (12:12) treatment having largest range, then the 12°C (16:18) treatment was next with 18.48-22.48% DW, and the 15°C (12:12) treatment had the lowest protein range with 16.48-18% DW. These results are in the range of protein content previously reported for brown seaweeds of 5-20%. Total polysaccharide content ranged from 9.6-16.2% DW with the highest content of 16.2% DW obtained for the 15 °C – (12:12) treatment, and the lowest total polysaccharide content of 9.6% DW obtained for the 12 °C (16:18) treatment. After 66 days of cultivation, the highest yield of sulphated polysaccharides of 0.4% DW was obtained for the 12 °C (12:12) treatment. Total fatty acids were analysed, with the highest polyunsaturated fatty acid content of 60.4% detected in the 12 °C (12:12) treatment. This study demonstrates that temperature and photoperiod are factors impacting juvenile sporophyte growth, biomass accumulation and biochemical composition. The study showed the least stressed sporophytes produced the most potentially beneficial nutritional or bioactive profile.

Solar vapour generation technology has emerged as a promising approach for reducing the global problem of water shortage issues via the solar water interfacial evaporation technique utilised for water purification. However, achieving superior light absorption and a high evaporation rate in a solar evaporator remains challenging. Here, we show that high solar interfacial water evaporation rates can be achieved using a natural and sustainable biomaterial, diatom frustules, decorated with silver nanoparticles made using a one-pot synthesis method. The species of diatom selected for this study was Actinocyclus sp. that has complex nano-and micro structured surfaces and air pores that lead to multiple light scattering. The absorptance before and after silver nanoparticle coating was measured after creating a thin frustule layer on a hydrophobically treated quartz substrate. It was found that the cleaned and uncoated frustules had zero absorptance from 400 nm to 1200 nm. However, silver nanoparticles coated frustules showed a large broadband absorptance up to 90 % from 400 nm to 1200 nm, covering most of the solar spectrum, due to localised surface plasma resonance and multiple light scattering in the air pores. The frustules were floated on the surface of a water droplet for solar water interfacial evaporation rate measurements. A high evaporation rate of 5.4 kg m- 2 h-1 under 1 sun irradiation was found for silver nanoparticles decorated frustules and for a droplet volume of 10 mm3. This is significantly larger than that found for frustules without silver nanoparticles or bare water where the evaporation rates were 1.7 kg m-2 h-1 and 1.2 kg m- 2 h-1, respectively. Moreover, increasing the number of floating frustules per drop resulted in a factor of 1.67 enhancement. Our results show that research into silver nanoparticle decorated frustules can potentially provide a novel route for fabricating a high-performance solar vapour generator.

Bioactive peptides range in size from 2–30 amino acids and may be derived from any protein-containing biomass using hydrolysis, fermentation or high-pressure processing. Pro-peptides or cryptides result in shorter peptide sequences following digestion and may have enhanced bioactivity. Previously, we identified a protein hydrolysate generated from Laminaria digitata that inhibited ACE-1 in vitro and had an ACE-1 IC50 value of 590 µg/mL compared to an ACE-1 IC50 value of 500 µg/mL (~2.3 µM) observed for the anti-hypertensive drug Captopril©. A number of peptide sequences (130 in total) were identified using mass spectrometry from a 3 kDa permeate of this hydrolysate. Predicted bioactivities for these peptides were determined using an in silico strategy previously published by this group utilizing available databases including Expasy peptide cutter, BIOPEP and Peptide Ranker. Peptide sequences YIGNNPAKGGLF and IGNNPAKGGLF had Peptide Ranker scores of 0.81 and 0.80, respectively, and were chemically synthesized. Synthesized peptides were evaluated for ACE-1 inhibitory activity in vitro and were found to inhibit ACE-1 by 80 ± 8% and 91 ± 16%, respectively. The observed ACE-1 IC50 values for IGNNPAKGGLF and YIGNNPAKGGLF were determined as 174.4 µg/mL and 133.1 µg/mL. Both peptides produced sequences following simulated digestion with the potential to inhibit Dipeptidyl peptidase IV (DPP-IV).

Aquaculture is a global-scale industry providing sustainable production of protein-rich foods required to feed the growing world population. Microalgae cultivation in aquaculture bioreactors can exude extracellular polymeric substances leading to biofouling of culture infrastructure and increased algal disease risk. A structure-behaviour relationship was developed by examining how the surface wettability of a range of functional nanocoatings impacts the extent of biofouling during exposure to continuous microalgae culture under normal hydrodynamic conditions. High-wetting (hydrophilic) surfaces were found to reduce biofouling better than water-repelling (hydrophobic) surfaces. Low toxicity in conjunction with antifouling behaviour was found for pulsed plasma poly(4-vinylpyridine) coated bioreactor surfaces (water contact angle = 38 +/- 5 degrees) towards the marine microalgal species Chaetoceros calcitrans, Chaetoceros mulleri, and Tisochrysis lutea (T-Iso), which are commonly grown as aquaculture food.

Seaweeds have a long history of use as both food and medicine, especially in Asian cultures. Moreover, there is growing interest in the use of seaweed ingredients and bioactive compounds in pharmaceutical and nutraceutical products. One ailment that seaweed bioactive compounds may impact is hypertension caused by the enzyme Angiotensin Converting Enzyme 1 (ACE-1; EC 3.4.15.1), found within the Renin-Angiotensin Aldosterone System (RAAS), which causes vasoconstriction of blood vessels, including veins and arteries. The aim of this paper is to generate bioactive peptide containing protein hydrolysates from the brown seaweed Laminaria digitata (Hudson) JV Lamouroux 1813. Proteins were extracted from this seaweed by disrupting the seaweed cell wall using a combination of carbohydrases and proteolytic enzymes. Bioactive peptide containing permeates were generated from L. digitata protein hydrolysates, and both hydrolysates and permeates were screened for their ability to inhibit the enzyme ACE-1. The protein content of the permeate fractions was found to be 23.87% compared to the untreated seaweed, which contained 15.08% protein using LECO analysis. Hydrolysis and filtration resulted in a "white" protein powder, and the protein content of this powder increased by 9% compared to the whole seaweed. The total amino acid (TAA) content of the L. digitata protein permeate was 53.65 g/100 g of the sample, and contains over 32% essential amino acids (EAA). Furthermore, the L. digitata permeate was found to inhibit the ACE-1 enzyme by 75% when compared to the commercial drug Captopril© when assayed at a concentration of 1 mg/mL. The inhibition of ACE-1 (the IC50 value) of 590 µg/mL for the L. digitata permeate compares well with Captopril©, which had 100% inhibition of ACE-1, with an IC50 value of 500 µg/mL. This study indicates that there is potential to develop protein powders with ACE-1 inhibitory bioactivities from the brown seaweed L. digitata using enzymatic hydrolysis as a cell disruption and protein extraction/hydrolysate generation procedure.

Fucoxanthin is a carotenoid in algae with purported beneficial health-related properties including antioxidant, anti-photoaging, anti-metastasis, anti-hypertensive activity and more. These properties give fucoxanthin the potential to be used in cosmetic, dietary, and medicinal applications. This study evaluates the use of deep eutectic solvents (DESs) to extract fucoxanthin from the microalgae Tisochrysis lutea. Conductor-like Screening Model for Real Solvents (COSMO-RS) was used to screen the performance of 24 different types of DESs in the extraction of fucoxanthin based on their calculated capacities. Experimental extraction validation was then carried out using the 6 top-ranked DESs. The experimental results revealed that the extraction capacity of the thymol: dodecanoic acid DES (1.25: 1 molar ratio) for fucoxanthin was the most efficient (7.69 mg/g dry biomass weight (DW)) among the DESs explored under the screening conditions and was higher than the capacity of the conventional solvents methanol (6.29 mg/g DW) and ethanol (6.75 mg/g DW). This corresponded with COSMORS screening results. Then, the optimisation of extraction conditions for fucoxanthin using thymol: dodecanoic acid DES was further investigated, revealing that the highest yield of fucoxanthin (22.03 mg/g DW) was extracted at optimum experimental conditions at a temperature of 36.2. C, stirring time of 2.58 h, and the biomass percentage of 11.36 %. Additionally, fucoxanthin showed good stability in thymol: dodecanoic acid DES over eleven days of storage. After seven extraction cycles, the final fucoxanthin concentration (13.06 mg/mL DES) resulted in a good reusability of the terpene-based food safe DES.

The agricultural production of ruminants is responsible for 24% of global methane emissions, contributing 39% of emissions of this greenhouse gas from the agricultural sector. Strategies to mitigate ruminant methanogenesis include the use of methanogen inhibitors. For example, the seaweeds Asparagopsis taxiformis and Asparagopsis armata included at low levels in the feed of cattle and sheep inhibit methanogenesis by up to 98%, with evidence of improvements in feed utilisation efficiency. This has resulted in an increasing interest in and demand for these seaweeds globally. In response, research is progressing rapidly to facilitate Asparagopsis cultivation at large scale, and to develop aquaculture production systems to enable a high quality and consistent supply chain. In addition to developing robust strategies for sustainable production, it is important to consider and evaluate the benefits and risks associated with its production and subsequent use as an antimethanogenic feed ingredient for ruminant livestock. This review focuses on the relevant ruminal biochemical pathways, degradation, and toxicological risks associated with bromoform (CHBr3), the major active ingredient for inhibition of methanogenesis in Asparagopsis, and the effects that production of Asparagopsis and its use as a ruminant feed ingredient might have on atmospheric chemistry.

Seaweeds have a long history of use as food, as flavouring agents, and find use in traditional folk medicine. Seaweed products range from food, feed, and dietary supplements to pharmaceuticals, and from bioenergy intermediates to materials. At present, 98% of the seaweed required by the seaweed industry is provided by five genera and only ten species. The two brown kelp seaweeds Laminaria digitata, a native Irish species, and Macrocystis pyrifera, a native New Zealand species, are not included in these eleven species, although they have been used as dietary supplements and as animal and fish feed. The properties associated with the polysaccharides and proteins from these two species have resulted in increased interest in them, enabling their use as functional foods. Improvements and optimisations in aquaculture methods and bioproduct extractions are essential to realise the commercial potential of these seaweeds. Recent advances in optimising these processes are outlined in this review, as well as potential future applications of L. digitata and, to a greater extent, M. pyrifera which, to date, has been predominately only wild-harvested. These include bio-refinery processing to produce ingredients for nutricosmetics, functional foods, cosmeceuticals, and bioplastics. Areas that currently limit the commercial potential of these two species are highlighted.

Microbial electrogenic behaviour is well characterised in prokaryotes, including the exo-electrogenic soil bacteria (‘metal breathers’) and cyanobacteria, some of which can perform a light-induced donation of electrons to electrochemical devices. Two main methods of electron donation are proposed in these organisms; mobile electron shuttles (redox mediators), and direct electron transport where redox active moieties embedded in the bounding membrane of the organisms provide electrical connection. In this study a photosynthetic microbial fuel cell was used to investigate the mechanism of electron donation from six benthic cyanobacteria to an external electrode. There was no evidence of mobile electron shuttles donating electrons to the bio-electrochemical system using electrochemical analysis by linear sweep voltammetry in any of the species studied. This indicates the possibility that all the benthic species investigated may use direct electron transport as a mechanism of electron donation, which is better recognised in single-celled planktonic species.

Biology and biotechnological applications of microalgae and photosynthetic prokaryotes: part 2 Julian J. Eaton-Rye , Benoit Guieysse , Michael A. Packer , Tina C. Summerfield d and Susanna A. Wood c Department of Biochemistry, University of Otago, Dunedin, New Zealand; School of Food & Advanced Technology, Massey University, Palmerston North, New Zealand; Cawthron Institute, Nelson, New Zealand; Department of Botany, University of Otago, Dunedin, New Zealand

In bivalve hatcheries, microalgae production accounts for a large proportion of hatchery operation costs. A reliable supply of good quality algae is essential for optimal output. Two commercially important algal species, Tisochrysis lutea (T-Iso) and Chaetoceros calcitrans were grown in batch culture under optimal and high-pH conditions for 7 and 5 days respectively. A suite of parameters were compared to identify those that could be considered as early markers of algal stress. One day after inoculation of both algal species, carbon dioxide (CO2) addition was removed to cause the high pH treatment condition and cultures were monitored to determine any changes in algal health. A variety of indicators of algal function including photosynthetic parameters by Pulse Amplitude Modulation (PAM) fluorometry and morphological and functional changes by flow cytometry were determined in parallel during the pH stress to correlate them and identify parameters that could be used as an early indicator of decreasing algal health. The pH in the sub-optimal treatments was significantly higher compared with controls from 1 day after the removal of CO2 addition. At the same sampling time (Day 2), in the high-pH treatment, the PRI photosynthetic efficiency in the light measured by PAM fluorometry and, chlorophyll fluorescence and reactive oxygen species production measured by flow cytometry were significantly lower for T-Iso, compared with controls. In sub-optimal cultures of C. calcitrans, relative algal size, complexity, chlorophyll and neutral lipid content (as measured by flow cytometry) were higher as early as Day 2, compared with controls. Additionally, the bacterial abundance associated with T-Iso and C. calcitrans cells was increased in the high pH treatment compared with controls, from Day 6 and Day 5 respectively. These responses to a subtle negative change in the culture environment were detected 24 h prior to a change in cell density and indicate the promise of PAM fluorometry and flow cytometry as tools to provide a rapid, sensitive and reliable assessment of microalgal health in a hatchery setting. Such advances in algal health monitoring will improve bivalve production systems.

In order to determine if nitrous oxide (N2O) emissions could affect the sustainability of microalgae-based pond systems, N2O emissions were recorded from an outdoor 900 L pilot high rate algal pond (HRAP) fed primary wastewater over 1 year. The HRAP was mixed using a paddle wheel and operated at a hydraulic retention time (HRT) of 7.5-10 days. Direct N2O emissions ranged from 4.1 to 6400 mu g N-N2O.m(-2).d(-1) (median of 560 mu g N-N2O.m(-2).d(-1), n = 28) at 10 days HRT, and 70-18300 mu g N-N2O.m(-2).d(-1) (median of 4200 mu g N-N2O.m(-2)d(-1) n = 22) at 7.5 days HRT. Using 25-75% of the data, we estimated that HRAPs designed for nitrogen removal operated at 7.5 days HRT (Le. 9.5 m(2).capita(-1) required) would generate 12-53 g N2O.capita.yr(-1) which is 4-17 fold higher than the default value of 3.2 g N2O.capita.yr(-1) given by the Intergovernmental Panel on Climate Change for centralized wastewater treatment plants with controlled nitrification and denitrification steps. When indirect N2O emissions (via nitrogen discharge and ammonia volatilization) are included, a HRAP operated at 7.5 days HRT could generate total emissions equivalent to 21-138 g N2O.capita(-1).yr(-1). When expressed as a % of the nitrogen input load into the system, the HRAP direct emissions (Le. 0.13-0.57%) and total (Le. 0.23-1.5%) where within the range of 0-14.6% reported in the literature for centralized wastewater treatment.

Nitrous oxide (N2O) emissions have been repeatedly observed during microalgal cultivation and from microalgae-based ecosystems such as eutrophic lakes. Various studies have unambiguously demonstrated N2O synthesis by axenic unialgal cultures and identified several potential microalgal N2O pathways. Based on these data, several studies have also reported that N2O emissions during microalgal cultivation (for e.g., biofuel feedstock production) could be significant at large scale. In this review, we also conservatively estimate that the currently unaccounted N2O emissions from eutrophic lakes alone could yield global N2O emissions equating to 18% of the N2O currently accounted from all rivers, estuaries, and coastal zones. While these estimates are highly uncertain given the lack of knowledge in the area, they support a case for improving mechanistic understanding of pathways and key triggers of microalgal N2O synthesis considering that (i) microalgae are ubiquitously found in natural ecosystems and may be cultivated at a massive scale in the future; (ii) N2O synthesis by axenic microalgae cultures has been unambiguously demonstrated, and current knowledge provides the foundation for six putative N2O synthesis pathways in microalgae; (iii) N2O emissions have been repeatedly reported from a diverse range of aquatic ecosystems characterized by a high level of algal activity; (iv) the Intergovernmental Panel on Climate Change does not currently consider N2O emissions potentially generated during algal blooms or algae cultivation.

Biology and biotechnological applications of microalgae and photosynthetic prokaryotes: Part 1 Julian J. Eaton-Rye , Benoit Guieysse, Michael A. Packer , Tina C. Summerfield d and Susanna A. Wood c Department of Biochemistry, University of Otago, Dunedin, New Zealand; School of Food & Advanced Technology, Massey University, Palmerston North, New Zealand; Cawthron Institute, Nelson, New Zealand; Department of Botany, University of Otago, Dunedin, New Zealand

The therapeutic benefits of Greenshell™ mussel (GSM; Perna canaliculus) preparations have been studied using in vitro test systems, animal models, and human clinical trials focusing mainly on anti-inflammatory and anti-arthritic effects. Activity is thought to be linked to key active ingredients that include omega-3 polyunsaturated fatty acids, a variety of carotenoids and other bioactive compounds. In this paper, we review the studies that have been undertaken in dogs, cats, and horses, and outline new research directions in shellfish breeding and high-value nutrition research programmes targeted at enhancing the efficacy of mussel and algal extracts. The addition of GSM to animal diets has alleviated feline degenerative joint disease and arthritis symptoms, and chronic orthopaedic pain in dogs. In horses, GSM extracts decreased the severity of lameness and joint pain and provided improved joint flexion in limbs with lameness attributed to osteoarthritis. Future research in this area should focus on elucidating the key active ingredients in order to link concentrations of these active ingredients with their pharmacokinetics and therapeutic effects. This would enable consistent and improved efficacy from GSM-based products for the purpose of improved animal health.

Over the last decades, several studies have reported emissions of nitrous oxide (N2O) from microalgal cultures and aquatic ecosystems characterized by a high level of algal activity (e.g. eutrophic lakes). As N2O is a potent greenhouse gas and an ozone-depleting pollutant, these findings suggest that large-scale cultivation of microalgae (and possibly, natural eutrophic ecosystems) could have a significant environmental impact. Using the model unicellular microalga Chlamydomonas reinhardtii, this study was conducted to investigate the molecular basis of microalgal N2O synthesis. We report that C.reinhardtii supplied with nitrite (NO2-) under aerobic conditions can reduce NO2- into nitric oxide (NO) using either a mitochondrial cytochrome c oxidase (COX) or a dual enzymatic system of nitrate reductase (NR) and amidoxime-reducing component, and that NO is subsequently reduced into N2O by the enzyme NO reductase (NOR). Based on experimental evidence and published literature, we hypothesize that when nitrate (NO3-) is the main Nitrogen source and the intracellular concentration of NO2- is low (i.e. under physiological conditions), microalgal N2O synthesis involves the reduction of NO3- to NO2- by NR followed by the reduction of NO2- to NO by the dual system involving NR. This microalgal N2O pathway has broad implications for environmental science and algal biology because the pathway of NO3- assimilation is conserved among microalgae, and because its regulation may involve NO.

Biological photovoltaics (BPVs) are emerging as a potential sustainable energy-generating technology to convert solar energy into electrical energy. Although a great variety of photosynthetic biomaterials were studied in BPVs, cyanobacteria are considered as superior candidates because of their simpler physiology. To facilitate extracellular electron transfer (EET) from cyanobacteria to electrodes is the greatest challenge to improving the performance of BPVs. However, a systematic study comparing the photo-excited EET from such organisms is not yet reported. Here we report on a comparison of photocurrent density generated by benthic cyanobacteria, that is, two species of Leptolyngbya sp. (CAWBG62 and CAWBG100), one species from the order Chroococcales (CAWBG64), and a eukaryotic algae, Paulschulzia pseudovolvox (UKE). This algae and CAWBG100 were sourced from New Zealand, CAWBG62 and CAWBG64 were from Antarctica. We demonstrate EET mediated by three different electron transfer (ET) mediating systems on graphite electrodes. These are as follows: (I) [Os(2,2'-(bipyridine)(2)(polyvinyl-imidazole)(10)Cl](+/2+) (1:9) [Os-(bpy)PVI] (II) p-benzoquinone (PBQ) (III) [Os-(bpy)PVI] together with PBQ. The maximum photocurrent density of 47.2A cm(-2) was obtained from CAWBG64 mediated by (III) [Os-(bpy)PVI] together with PBQ.

Microbial fuel cells (MFCs) are bioelectrochemical systems (BESs) that exploit biological catalytic processes for the generation of electrical power or the accumulation of useful compounds. Photosynthetic MFCs (pMFCs) are those that utilise photosynthetic microorganisms, such as algae and cyanobacteria, to provide reducing power at the anode. A reproducible light-dependent electrogenic effect occurs as algae or cyanobacteria convert light to electrical energy in the BES. In addition to the generation of electricity, the phenomenon may be useful in niche circumstances such as for bioelectrosynthesis or for use in environmental biosensors. In this study we measure the effect of common toxicants (copper, thallium, zinc and glyphosate) on the electrogenic activity of electrode surface-dwelling algae and cyanobacteria. We observed a decrease in the light-dependent electrical response via these photosynthetic microorganisms in our pMFC that was proportional to the concentration of toxicants. This demonstrates the utility of these BESs as potential environmental biosensors where the metabolism of photosynthetic microorganisms acts to sense signals from the environment.