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Stretchable and self-adhesive conductive hydrogels hold significant importance across a wide spectrum of applications, including human-machine interfaces, wearable devices, and soft robotics. However, integrating multiple properties, such as high stretchability, strong interfacial adhesion, self-healing capability, and sensitivity, into a single material poses significant technical challenges. Herein, we present a multifunctional conductive hydrogel based on poly(acrylic acid) (PAA), dopamine-functionalized pectin (PT-DA), polydopamine-coated reduction graphene oxide (rGO-PDA), and Fe3+ as an ionic cross-linker. This hydrogel exhibits a combination of high stretchability (2000%), rapid self-healing (~ 94% recovery in 5 s), and robust self-adhesion to various substrates. Notably, the hydrogel demonstrates a remarkable skin adhesion strength of 85 kPa, surpassing previous skin adhesive hydrogels. Furthermore, incorporating rGO within the hydrogel network creates electric pathways, ensuring excellent conductivity (0.56 S m-1). Consequently, these conductive hydrogels exhibit strain-sensing properties with a significant increase in gauge factor (GF) of 14.6, covering an extensive detection range of ~ 1000%, fast response (198 ms) and exceptional cycle stability. These multifunctional hydrogels can be seamlessly integrated into motion detection sensors capable of distinguishing between various strong or subtle movements of the human body.

We investigated two non-ionising mutagens in the form of ultraviolet radiation (UV) and ethyl methanosulfonate (EMS) and an ionising mutagen (X-ray) as methods to increase fucoxanthin content in the model diatom Phaeodactylum tricornutum. We implemented an ultra-high throughput method using fluorescence-activated cell sorting (FACS) and live culture spectral deconvolution for isolation and screening of potential pigment mutants, and assessed phenotype stability by measuring pigment content over 6 months using high-performance liquid chromatography (HPLC) to investigate the viability of long-term mutants. Both UV and EMS resulted in significantly higher fucoxanthin within the 6 month period after treatment, likely as a result of phenotype instability. A maximum fucoxanthin content of 135 ± 10% wild-type found in the EMS strain, a 35% increase. We found mutants generated using all methods underwent reversion to the wild-type phenotype within a 6 month time period. X-ray treatments produced a consistently unstable phenotype even at the maximum treatment of 1000 Grays, while a UV mutant and an EMS mutant reverted to wild-type after 4 months and 6 months, respectively, despite showing previously higher fucoxanthin than wild-type. This work provides new insights into key areas of microalgal biotechnology, by (i) demonstrating the use of an ionising mutagen (X-ray) on a biotechnologically relevant microalga, and by (ii) introducing temporal analysis of mutants which has substantial implications for strain creation and utility for industrial applications.

Symbiodiniaceae form associations with extra- and intracellular bacterial symbionts, both in culture and in symbiosis with corals. Bacterial associates can regulate Symbiodiniaceae fitness in terms of growth, calcification and photophysiology. However, the influence of these bacteria on interactive stressors, such as temperature and light, which are known to influence Symbiodiniaceae physiology, remains unclear. Here, we examined the photophysiological response of two Symbiodiniaceae species (Symbiodinium microadriaticum and Breviolum minutum) cultured under acute temperature and light stress with specific bacterial partners from their microbiome (Labrenzia (Roseibium) alexandrii, Marinobacter adhaerens or Muricauda aquimarina). Overall, bacterial presence positively impacted Symbiodiniaceae core photosynthetic health (photosystem II [PSII] quantum yield) and photoprotective capacity (non-photochemical quenching; NPQ) compared to cultures with all extracellular bacteria removed, although specific benefits were variable across Symbiodiniaceae genera and growth phase. Symbiodiniaceae co-cultured with M. aquimarina displayed an inverse NPQ response under high temperatures and light, and those with L. alexandrii demonstrated a lowered threshold for induction of NPQ, potentially through the provision of antioxidant compounds such as zeaxanthin (produced by Muricauda spp.) and dimethylsulfoniopropionate (DMSP; produced by this strain of L. alexandrii). Our co-culture approach empirically demonstrates the benefits bacteria can deliver to Symbiodiniaceae photochemical performance, providing evidence that bacterial associates can play important functional roles for Symbiodiniaceae.

Fluorescence-Activated Cell Sorting (FACS) is a powerful method with many applications in microalgal research, especially for screening and selection of cells with improved phenotypes. However, the technology requires review of gene expression changes responsible for enhanced phenotypes in sorted populations. Phaeodactylum tricornutum cells were sorted using FACS with excitation/emission parameters targeted to favouring the industrially-relevant carotenoid fucoxanthin. The resulting cultures showed significantly higher growth rate (1.10 ×), biomass (1.30 ×), chlorophyll a levels (1.22 ×) and fucoxanthin content (1.28 ×) relative to the wild-type strain. RNA-seq was used to elucidate the underlying molecular-level regulatory changes associated with these traits and represents the first study do so on FACS-sorted microalgal cultures. Transcriptome analysis corroborated evidence of increased chlorophyll a and fucoxanthin, showing enrichment for the genes/pathways for tetrapyrrole biosynthesis and for suites of genes directly related to photosynthesis. Only three genes were upregulated in the MEP (non-mevalonate) pathway to carotenoid biosynthesis pathway, suggesting either a strong influence of IDI, CRTISO5 and ZEP1 on fucoxanthin biosynthesis or a post-transcriptional or post-translational mechanism for the observed increase in fucoxanthin content.

Underpinning primary food chains, atmospheric carbon cycling, and vital ecosystem functions are diatoms, a class of microalgae found ubiquitously in aquatic environments around the globe (Armbrust, 2009; Nelson et al., 1995). As with most organisms on earth climate change threatens their survival and distribution, therefore their ability to adapt to environmental drivers through phenotypic plasticity has become a topic of investigation in recent years (Cox, 2014; Sackett et al., 2013; Vartanian et al., 2009). Furthermore, diatoms are being seen in a new light thanks to recent endeavours to unravel the genomes of a broad range of species across the phylogenetic tree, including the currently underway ‘100 Diatom Genome Project’ and the “Earth BioGenome Project” project which aims to sequence over 3000 protozoa (Bowler et al., 2008; Armbrust, 2009, Joint Genome Institute, 2021; Earth BioGenome Project, 2022; Mock et al., 2022). Knowing the genome is however insufficient in understanding the complex responsivity of an organism exposed to variable environmental conditions, and thus a large-scale diatom phenotyping project is needed. Embarking on such a project that involves a multitude of diverse and intricate organisms will undoubtedly pose challenges. These hurdles stem not only from their extensive genetic diversity, but also from the complex endeavour of consolidating their phenomes. In adapting modern phenomics methods to bridge the genome-phenome gap in diatoms, multi-driver and multi-trait relationships must be considered across a range of species, in which many phenotypes may be expressed under different conditions (Chitwood and Topp, 2015). Armed with comprehensive genomic and phenomic datasets for a range of diatoms, we may be able to predict with more precision the effects of climate change on ecological and biogeochemical processes that are driven by diatom primary productivity.

Microalgae are of commercial interest for their ability to produce high-value compounds and their potential to be used as feedstock across numerous industries. The production of algal biomass and other algal-based products involves different upstream and downstream processing steps, including cultivation, harvesting, and extraction. In particular, the harvesting process involves the extraction of a condensed algal slurry from a watery growth medium. This process accounts for 20 to 30 % of the biomass production costs, creating technological and economic barriers. The conventional harvesting methods suffer from high costs, cross-contamination, and low yield. This study explores the use of a microfluidic technique, in particular, the rigid spiral microchannel, for ultra-high-throughput algae harvesting. We have designed a novel spiral channel that enables microalgae separation at high flow rates and spatial resolution, taking advantage of inertial microfluidic principles. The results from trials with surrogate microparticles and algal cells reveal that the microchannel has the potential to operate at 12 mL/min with separation efficiency >99 %. Our inertial microfluidic device operates at high flow rates as a single channel, can be multiplexed, and shows excellent potential for large-scale processing of microalgae cultures. In addition, the lower number of loops provides the system with reduced back pressure, making it more desirable for operation using a range of different pumps. Since the overall cost of microalgae dewatering is substantial at the industrial scale, the design and fabrication of low-cost devices are of great importance, similar to the one we have developed in this study.

Phenomics is a relatively new discipline of biology that has been widely applied in several fields, mainly in crop sciences. We reviewed the concepts used in this discipline (particularly for plants) and found a lack of consensus on what defines a phenomic study. Furthermore, phenomics has been primarily developed around its technical aspects (operationalization), while the conceptual framework of the actual research lags behind. Each research group has given its own interpretation of this 'omic' and thus unwittingly created a 'conceptual controversy'. Addressing this issue is of particular importance, as the experimental designs and concepts of phenomics are so diverse that it is difficult to compare studies. In this opinion article, we evaluate the conceptual framework of phenomics.

Diatoms are major producers of carbon and energy in aquatic ecosystems, however their ability to rapidly and successfully acclimate to wide ranging irradiances is poorly understood at the biochemical level. We applied complementary transcriptomic and metabolomic approaches using the model centric diatom Thalassiosira pseudonana to understand mechanisms regulating cell acclimation and growth under high and low light intensities. The integration of these omics data revealed specific mechanisms that shifted carbon and energy fluxes in T. pseudonana depending on light-driven growth rate. To support a growth rate of >1 d−1 in high light, cells upregulated metabolic pathways involved in the production of long chain fatty acids, glycolic acid, and carbohydrates. Under low light, cells maintained a growth rate of ≤0.2 d−1 by conserving photosynthetic energy through upregulation of carbon retention pathways (e.g., gluconeogenesis, glyoxylate cycle). The few significant metabolites detected in low light acclimated cells were associated with light harvesting, energy storage, and signalling. In particular, our metabolite data revealed that eicosanoic acid, a metabolite commonly involved in cellular signalling, may poise light limited cells for fast metabolic remodelling with improving light conditions. The combined physiological, gene expression and metabolite profiling data revealed key metabolic switch points that underpin diatom success and could be leveraged in cell-based models for predictions and manipulations of cell growth or bio-production.

Microalgae are photosynthetic organisms that can be grown in photobioreactors (PBRs). The light placement within the PBR is crucial to optimize growth. Currently, the light path is often estimated from various mathematical models, which may result in less efficient placements of lights. Here we describe a novel fluorescence imaging technique to map the light within a bioreactor. These light maps describe the photosynthetic photon flux density (PPFR) inside the PBR, resulting in a precise light pattern of the LEDs and potential light reflections of the reactor walls. Furthermore, when compared with conventional imaging measurements that uses visible light, the fluorescence imaging technique has the advantage that only fluorescence emissions of microalgae are recorded. Regions of the PBR that show fluorescence emission can be assumed to have photosynthetic activity with sufficient irradiance of the specific photosynthetic active radiation (PAR) wavelengths. This method is adaptable to complex photobioreactor geometries and could be used to identify light-saturated areas. Two microalgae species and three colours of LEDs (red, blue, and white) were analysed in regards to light penetration and light distribution at different cell concentrations.

Copper ion (Cu2+) and zinc ion (Zn2+) are widely co-existent in anaerobic digestion effluent as typical contaminants. This work aims to explore how Cu2+-Zn2+ association affects physiological properties of S. platensis using Schlösser medium (SM) and sterilized anaerobic digestion effluent (SADE). Microalgae cells viability, biochemical properties, uptake of Cu2+ and Zn2+, and risk assessment associated with the biomass reuse as additives to pigs were comprehensively assessed. Biomass production ranged from 0.03 to 0.28 g/L in SM and 0.63 to 0.79 g/L in SADE due to the presence of Cu2+ and Zn2+. Peak value of chlorophyll-a and carotenoid content during the experiment decreased by 70-100% and 40-100% in SM, and by 70-77% and 30-55% in SADE. Crude protein level reduced by 4-41% in SM and by 65-75% in SADE. The reduction ratio of these compounds was positively related to the Cu2+ and Zn2+ concentrations. Maximum value of saturated and unsaturated fatty acids was both obtained at 0.3 Cu + 2.0 Zn (50.8% and 22.8%, respectively) and 25% SADE reactors (33.8% and 27.7%, respectively). Uptake of Cu in biomass was facilitated by Zn2+ concentration (> 4.0 mg/L). Risk of S. platensis biomass associated with Cu2+ was higher than Zn2+. S. platensis from SM (Cu2+ ≤ 0.3 mg/L and Zn2+ ≤ 4.0 mg/L) and diluted SADE (25% and 50% SADE) reactors could be used as feed additives without any risk (hazard index <1), which provides sufficient protein and fatty acids for pig consumption. These results revealed the promising application of using S. platensis for bioremediation of Cu2+ and Zn2+ in anaerobic digestion effluent and harvesting biomass for animal feed additives.

Microfluidic platforms have evolved in recent years to assist researchers and biologists in performing biological and medical assays for cell separation and sorting. These microfluidic systems are competitive alternatives to conventional methods in terms of cost, sample volume reduction, high sensitivity, portability, fast processing, and elimination of chemical labels required for detection. In this chapter, these techniques have been classified into two major groups, active and passive, based on their energy intake and operating standards. Each separation technique was described briefly, and their operational principles were explained in detail. To specify the applications of each technique, the most recent popular examples have been explained along with common metrics used for the evolution of microfluidic system, including efficiency, accuracy, and throughput. This chapter is designed to be helpful for researchers who aim to develop unique microfluidic separator systems with further innovative designs in microfluidic platforms.

The effects of microalgae harvesting methods on microalgal biomass quality were evaluated using three species namely the freshwater green alga Chlorella vulgaris, marine red alga Porphyridium purpureum and marine diatom Phaeodactylum tricornutum. Harvesting efficiencies of polyacrylamide addition, alkaline addition, and centrifugation ranged from 85 to 95, 59-92 and 100%, respectively, across these species. Morphology of the harvested cells (i.e. compromised cell walls) was significantly impacted by alkaline pH-induced flocculation for all three species. Over 50% of C. vulgaris cells were compromised with alkaline pH compared to < 10% with polyacrylamide and centrifugation. The metabolic profiles varied depending on harvesting methods. Species-specific decrease of certain metabolites was observed. These results suggest that the method of harvest can alter the metabolic profile of the biomass amongst the three harvesting methods, polyacrylamide addition showed higher harvesting efficiency with less compromised cells and higher retention of industry important biochemicals.

The field of research that explores the use of microalgae in biomedicine and health is complex and diverse. Numerous research avenues currently explore the use of microalgae in biomedicine and heath such as: focusing on establishing and boosting nutritional profiles for food applications; identification, characterisation and utilisation of microalgal metabolites with biological activity as functional ingredients and/or drugs; utilisation of recombinant technology to genetically modify the algae for use as production systems for enzymes, antibodies, growth factors, drugs, and vaccines; or the use of microalgae as a source of “biomaterial” for use in applications such as drug carriers or cellular scaffolds for tissue engineering. To illustrate the diversity of microalgae and its potential for utilisation in a wide variety of biomedical and heath care applications, this chapter will present a concise overview of this broad applicability of microalgae in biomedicine and health, while highlighting research that is also occurring into the production and biorefinery of these compounds to facilitate a viable transition from laboratory to commercial production. Thus, this chapter aims to bridge the knowledge gap between both existing and potentially new algae applications, in particular, the use of microalgae as a source of “biomaterials” for biomedicine and health applications.

Carbon capture and utilization (CCU) is an emerging technology with commercial potential to convert atmospheric carbon dioxide (CO2) into net zero or negative emission products. In microalgae-based CCU, microalgae utilize CO2 and sunlight to generate biomass for commercial applications. This paper reviews the current state of microalgal culture development for CCU and highlights its potential contribution to addressing climate change challenges. Current microalgal culture systems have not been designed for high throughput biomass growth and carbon capture. Raceways, high-rate algal ponds, and photobioreactors are the most widely used for microalgal cultivation at a large-scale. The limitations of these systems are related to microalgal growth requirements. Ponds are operated at narrow depth to ensure sufficient light distribution and thus need a large land surface. CO2 gas needs to be in a dissolved form for efficient utilization by microalgae. Innovative system designs to achieve optimized distribution of light, nutrient, and CO2 utilization for enhanced biomass production are crucial to achieve large-scale CO2 capture by microalgae. Data corroborated in this review highlights several innovative techniques to deliver CO2 effectively and enhance light illumination to microalgal cells. Submerged and internal illuminations can enhance light distribution without compromising culture volume and land requirements. CO2 delivery technique selections mainly depend on CO2 sources. The carbonation column appears to be the best option regarding efficiency, easy operation, and simple design. The downstream processes of microalgal culture (i.e. harvesting, biomass utilization, and water reuse) are important to make microalgae-based CCU a significant contribution to global carbon mitigation solutions.

Food shortage and finite planetary resources are the most significant problems that mankind must deal with in the 21st century. Climate change, diminishing arable land and potable water have worsened the conditions and conventional nutrient sources are becoming unsustainable. The increasing global population continues to drive the search for sustainable, safe and alternative nutrient sources to meet the demand for food. The high nutrient content of macro- and micro-nutrients in microalgae, and the environmentally friendly traits of microalgae like CO2 consumption, not needing arable land or drinkable water have made microalgae a promising alternative food source. Furthermore, due to the health benefits of their derived bioactive compounds, the demand for microalgal supplements are becoming increasingly popular. Despite the potential of microalgae to be utilized as a food or food ingredient, their incorporation into foods is hindered due to several obstacles. The first obstacle is the sensory attributes of many species of microalgae, including the fishy taste, odour and colour, that are not pleasant for most people. The high costs of downstream processing and harvesting of microalgae are the second problem. The third obstacle are the legislative issues relating to the incorporation of microalgae into food products, particular if it is derived from novel species of microalgae. In this respect, this review aims to summarise the current situation of marketed microalgae-based products and products that are still under research and development, whilst providing further insight into the challenges and obstacles that can limit microalgae utilization as food ingredients.

The green microalga Chlamydomonas reinhardtii is emerging as a promising cell biofactory for secreted recombinant protein (RP) production. In recent years, the generation of the broadly used cell wall-deficient mutant strain UVM4 has allowed for a drastic increase in secreted RP yields. However, purification of secreted RPs from the extracellular space of C. reinhardtii strain UVM4 is challenging. Previous studies suggest that secreted RPs are trapped in a matrix of cell wall protein aggregates populating the secretome of strain UVM4, making it difficult to isolate and purify the RPs. To better understand the nature and behaviour of these extracellular protein aggregates, we analysed and compared the extracellular proteome of the strain UVM4 to its cell-walled ancestor, C. reinhardtii strain 137c. When grown under the same conditions, strain UVM4 produced a unique extracellular proteomic profile, including a higher abundance of secreted cell wall glycoproteins. Further characterization of high molecular weight extracellular protein aggregates in strain UVM4 revealed that they are largely comprised of pherophorins, a specific class of cell wall glycoproteins. Our results offer important new insights into the extracellular space of strain UVM4, including strain-specific secreted cell wall proteins and the composition of the aggregates possibly related to impaired RP purification. The discovery of pherophorins as a major component of extracellular protein aggregates will inform future strategies to remove or prevent aggregate formation, enhance purification of secreted RPs, and improve yields of recombinant biopharmaceuticals in this emerging cell biofactory. KEY POINTS: • Extracellular protein aggregates hinder purification of recombinant proteins in C. reinhardtii • Unassembled cell wall pherophorins are major components of extracellular protein aggregates • Known aggregate composition informs future strategies for recombinant protein purification.

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Marine debris has become a global problem affecting coral health around the globe. However, the photophysiological responses of corals to marine debris stress remain unclear. Therefore, this study firstly investigated transparent and opaque plastic bag shading and fishing nets directly contacting the coral. Photosynthetic performance, pigment content, symbiont density, and calcification rate of a branching coral Pocillopora acuta and a massive coral Porites lutea were investigated after 4 weeks of exposure to marine debris. The results show that the maximum quantum yield of PSII significantly decreased in P. lutea with all treatments, while P. acuta showed no effect on the maximum quantum yield of PSII from any treatments. Transparent plastic bag shading does not affect P. acuta, but significantly affected the maximum photochemical efficiency of P. lutea. Photoacclimation of cellular pigment content was also observed under opaque plastic bag shading for both species at week 2. Fishing nets had the strongest effect and resulted in P. acuta bleaching and P. lutea partial mortality as well as a decline in zooxanthellae density. Calcification rate of P. acuta significantly decreased with treatments using opaque plastic bag and fishing net, but for P. lutea only the treatment with fishing net gave any observable effects. This study suggests that the sensitivities of corals to marine debris differ strongly by species and morphology of the coral.

This study aims to elucidate the mechanisms governing the harvesting efficiency of Chlorella vulgaris by flocculation using a cationic polymer. Flocculation efficiency increased as microalgae culture matured (i.e. 35-45, 75, and > 97% efficiency at early, late exponential, and stationary phase, respectively. Unlike the negative impact of phosphate on flocculation in traditional wastewater treatment; here, phosphorous residue did not influence the flocculation efficiency of C. vulgaris. The observed dependency of flocculation efficiency on growth phase was driven by changes in microalgal cell properties. Microalgal extracellular polymeric substances (EPS) in both bound and free forms at stationary phase were two and three times higher than those at late and early exponential phase, respectively. Microalgae cells also became more negatively charged as they matured. Negatively charged and high EPS content together with the addition of high molecular weight and positively charged polymer could facilitate effective flocculation via charge neutralisation and bridging.

Peridinin-Chlorophyll a-Proteins (PCP) are the major light harvesting proteins in photosynthetic dinoflagellates. PCP shows great variation in protein length, pigment ratio, sequence, and spectroscopic properties. PCP conjugates (PerCP) are widely used as fluorescent probes for cellular and tissue analysis in the biomedical field. PCP consists of a peridinin carotenoid; thereby, it can potentially be used as a bioactive compound in pharmaceutical applications. However, the biological activities of PCP are yet to be explored. In this study, we extracted, purified, and partially characterised the PCP from Symbiodinium tridacnidorum (CS-73) and explored its antioxidant, anti-cancer and anti-inflammation bioactivities. The PCP was purified using an ÄKTA™ PURE system and predicted to be of 17.3 kDa molecular weight (confirmed as a single band on SDS-PAGE) with an isoelectric point (pI) 5.6. LC-MS/MS and bioinformatic analysis of purified PCP digested with trypsin indicated it was 164 amino acids long with >90% sequence similarity to PCP of SymA3.s6014_g3 (belonging to clade A of Symbiodinium sp.) confirmed with 59 peptide combinations matched across its protein sequence. The spectroscopic properties of purified PCP showed a slight shift in absorption and emission spectra to previously documented analysis in Symbiodinium species possibly due to variation in amino acid sequences that interact with chl a and peridinin. Purified PCP consisted of a 19-amino-acid-long signal peptide at its N terminal and nine helixes in its secondary structure, with several protein binding sites and no DNA/RNA binding site. Furthermore, purified PCP exhibited antioxidant and in vitro anti-inflammation bioactivities, and anti-cancer activities against human metastatic breast adenocarcinoma (MDA-MB-231) and human colorectal (HTC-15) cancer cell lines. Together, all these findings present PCP as a promising candidate for continued investigations for pharmaceutical applications to cure chr

Hydraulic retention time (HRT) in wastewater treatment high rate algal ponds is an important operational parameter that determines both nutrient loading and effluent water quality. Shorter HRT increases the influent nutrient loading, and ultimately, areal microalgal productivity, but decreases effluent quality. Recycling a proportion of the effluent water can decrease the HRT whilst maintaining the same nutrient loading. This study investigated how partially and fully harvested recycled effluent affected microalgal performance, with respect to nutrient removal and biomass production in high rate algal mesocosms operated on shortened (summertime) 4-day HRT compared to longer (wintertime) 8-day HRT. Recycling partially harvested effluent water, still containing some microalgal/bacterial biomass, negatively affected the net biomass production, relatively to all other treatments. This was due to the diminished light climate and photosynthetic potential within the mesocosm, as a result of biomass loading. On the other hand, recycling fully harvested effluent to decrease the HRT by half did allow for higher daily biomass productivity compared to high rate algal mesocosms run on an 8-day HRT. However, it did not result in any increase in wastewater treatment over that in the 8-day full-load HRT treatment but had higher effluent quality than that of the 4-day full-load HRT treatment. Recycling effluent has the potential to increase microalgal biomass production, without degrading effluent quality, to further improve the economics of coupled wastewater treatment and resource recovery, but complete or near-complete harvesting of biomass is required.

Wild marine microalgal consortia may overcome a number of challenges of growing domesticated strains in outdoor open pond systems, such as poor tolerance of fluctuating environment and pond crashes. We investigated the performance of wild marine microalgal communities grown under four ammoniacal nitrogen loads: (i) 6.25 g m−3 (0.5 ×), (ii) 12.5 g m−3 (1 ×), (iii) 25 g m−3 (2 ×) and (iv) 50 g m−3 (4 ×), with respect to biomass yield, macromolecular composition and community membership. Volatile suspended solids (organic matter) increased with increasing ammonia load, with 4 × (210 ± 15 g m−3) significantly higher (p < 0.01) than 2 × (167 ± 24 g m−3), 1 × (127 ± 8 g m−3) and 0.5 × (97 ± 13 g m−3), but the response was not linear. Supplemental dissolved inorganic phosphorus did not increase overall biomass production. Percentage protein per unit biomass significantly increased with increased ammonia, with 2 × and 4 × significantly higher (p < 0.05) than 0.5 × and 1 × , but this came at the expense of carbohydrates. Percentage carbohydrate was significantly lower (p < 0.01) in the 2 × and 4 × treatments. A total of 13 species, including eight dominant species, were recorded across all treatments. As ammonia increased, the community shifted from a diatom (Amphora ovalis, Coscinodiscus radiatus, Minidiscus sp.)-dominated community (by biovolume) to a green alga–dominated community, while Nannochloropsis sp. was numerically dominant across all treatments. These results indicate the capability of marine microalgae to utilise waste centrate as a rich nutrient source. Further investigations under outdoor conditions, where multiple environmental stressors may intensify differential responses amongst individual species, are needed to better understand community response.

This study addresses the challenge of microalgae harvesting through the development of flocculants. Two positively charged cationic polymers including poly[2 (acryloyloxy)ethyl]trimethylammonium chloride (PAETAC) and poly(3 acrylamidopropyl)trimethylammonium chloride (PAmPTAC) were synthesized using the UV-induced radical polymerization, for harvesting both freshwater and marine microalgae. The results show that the synthesized polymers have excellent flocculation performance for both freshwater green microalgae (Chlorella vulgaris) and marine red microalgae (Porphyridium purpureum). PAETAC outperformed PAmPTAC for both Chlorella vulgaris and Porphyridium purpureum microalgae. The optimal PAETAC doses for Chlorella vulgaris and Porphyridium purpureum microalgae were 50 and 4.8 mg/g of dry biomass while the optimal PAmPTAC doses were 252 and 35 mg/g of dry biomass respectively. Additionally, the floc formation with the PAETAC was more stable than PAmPTAC, which supported the dewatering step via sieving. The superior performance can be attributed to the higher molecular weight of the PAETAC polymer when compared to the PAmPTAC polymer. In comparison to commercially available polydiallyldimethylammonium chloride (PolyDADMAC), the newly synthesised PAETAC and PAmPTAC polymers demonstrated superior flocculation efficiency at a lower dose. The findings of this study established a platform technology for designing and synthesising cationic flocculants for use in microalgae harvesting.

High rate algal ponds are an established cost-effective and efficient upgrade to conventional wastewater treatment ponds for the biological treatment of wastewaters. However, few studies have investigated ecosystem metabolism and its drivers in these ponds. Hourly, daily and seasonal changes in rates of gross primary production, net ecosystem production and ecosystem respiration were determined from automated dissolved oxygen, pH and temperature measurements in full-scale high rate algal ponds over a two-year period. The open water metabolism model was used to assess the dynamics of pond metabolism against a number of measured environmental variables. For the most part, net ecosystem production was positive, meaning that the pond was in net autotrophy, with microalgal photosynthetic production exceeding respiratory organic matter consumption. pH had a negative influence on ecosystem respiration, with respiration rates increasing as diurnal pH increased. Similarly, free ammonia concentration reduced gross primary production rates. Modelled CO2 addition to maintain pH 8, resulted in decreased ecosystem respiration and increased net ecosystem production, particularly in summer with a 50% increase in net ecosystem production. However, modelled CO2 addition did not influence net ecosystem production during winter. The use of the Datasondes coupled with the open water metabolism model provides a cost-effective tool for improved high rate algal pond management through the capture of high frequency metabolism parameters. Better understanding of how the high rate algal pond environment affects both photosynthesis and respiratory losses, will help improve real-time management of the pond, including ammonia and CO2 loading management, to improve effluent quality and biomass yields and reduce excess CO2 off-gassing to atmosphere.

Microalgae produce a broad range of organic compounds that are increasingly being recognised for their value in novel product production and biotechnological applications. Most microalgae are photoautotrophic, but some are capable of either mixotrophy or heterotrophy. Reported enhanced biomass yields or contrasting metabolite profiles compared to autotrophic growth improve the economics of large-scale production of microalgae, which currently limits industrial applications. Here, the potential of a high-throughput method for the rapid screening of microalgal metabolism was assessed against 95 different carbon sources, using the cost-effective Biolog plate. Of the 5 microalgae tested, Desmodesmus communis (30 carbon sources) and Chlorella vulgaris (19 carbon sources) had the highest number of positive responses to carbon sources, whereas Chlorella sorokiniana had the most negative (toxic) response to the various carbon sources (77 carbon sources). Comparison of Biolog plate results with traditional culture techniques showed good agreement. Species with a high number of positive responses on the Biolog plate exhibited the highest biomass yield under heterotrophic conditions, whilst those with low number of positive responses exhibited the highest biomass yield under autotrophic conditions, using traditional culturing techniques. While the use of these plates is limited to obtaining axenic lines of microalgal species, the method provided a high-throughput assessment of carbon source metabolism, without the expense of undertaking large, laborious traditional culturing assessments. Such high-throughput assessments can be regarded as useful tools for progressing species selection, metabolic capacity and optimal culture conditions for microalgal biotechnology applications.

Microalgal biotechnology shows considerable promise as a sustainable contributor to a broad range of industrial avenues. The field is however limited by processing methods that have commonly hindered the progress of high throughput screening, and consequently development of improved microalgal strains. We tested various microplate reader and flow cytometer methods for monitoring the commercially relevant pigment fucoxanthin in the marine diatom Phaeodactylum tricornutum. Based on accuracy and flexibility, we chose one described previously to adapt to live culture samples using a microplate reader and achieved a high correlation to HPLC (R2 = 0.849), effectively removing the need for solvent extraction. This was achieved by using new absorbance spectra inputs, reducing the detectable pigment library and changing pathlength values for the spectral deconvolution method in microplate reader format. Adaptation to 384-well microplates and removal of the need to equalize cultures by density further increased the screening rate. This work is of primary interest to projects requiring detection of biological pigments, and could theoretically be extended to other organisms and pigments of interest, improving the viability of microalgae biotechnology as a contributor to sustainable industry.

Microalgae are increasingly recognised as valuable feedstock for novel product production and biotechnological applications, but high costs associated with both the culturing and harvesting of microalgae remain one of the major bottlenecks. Mixotrophy and heterotrophy are increasingly being recognised as potentially cost-effective growth strategies for mass culture, but the response of microalgae to alternative growth strategies is not universal amongst species. This study assessed the response of four species from related genera (Acutodesmus acutiformis, Desmodesmus communis, Scenedesmus obtusus, and Tetradesmus dimorphus) to the different growth conditions, autotrophic, mixotrophic, and heterotrophic with inorganic nutrients and heterotrophic with organic nutrients. While all four related genera were capable of growing mixotrophically and heterotrophically, the response was not universal across all four species. Biomass production was highest under heterotrophy for three out of the four species, while production was inhibited in T. dimorphus, relative to autotrophy. The percentage lipids and proteins varied amongst all four species under the four different growth strategies. Percentage lipids were highest under autotrophy and mixotrophy for both A. acutiformis and D. communis, while percentage lipids were lowest in S. obtusus under autotrophic conditions. For T. dimorphus percentage, lipids did not vary across treatments. The reverse occurred for percentage proteins, being highest for both A. acutiformis and D. communis under heterotrophy and highest for S. obtusus under autotrophic conditions. Percentage protein did not vary across treatments for T. dimorphus. Coenobium size and total numbers varied amongst treatments for all four species, with no consistent between the species. Microalgal performance under either heterotrophic or mixotrophic growth was species dependent. For commercial applications, these results demonstrate the importance of assessing the respo

Rapid light curves are one of the most widely used methods for assessing the physiological state of photosynthetic organisms. While the method has been applied in a range of physiological studies over the last 20 years, little progress has been made in adapting it for the new age of multi-parametric phenotyping. In order to advance research that is aimed at evaluating the physiological impact of multiple factors, the Phenoplate was developed: a simultaneous assessment of temperature and light gradients. It was used to measure rapid light curves of three marine microalgae across a temperature gradient and altered phosphate availability. The results revealed that activation of photoprotective mechanisms occurred with high efficiency at lower temperatures, and relaxation of photoprotection was negatively impacted above a certain temperature threshold in Tetraselmis sp. It was observed that Thalassiosira pseudonana and Nannochloropsis oceanica exhibited two unique delayed non-photochemical quenching signatures: in combinations of low light with low temperature, and darkness with high temperature, respectively. These findings demonstrate that the Phenoplate approach can be used as a rapid and simple tool to gain insight into the photobiology of microalgae.

[This corrects the article DOI: 10.3389/fmicb.2019.01011.].

Seagrasses are valuable sources of food and habitat for marine life and are one of Earth's most efficient carbon sinks. However, they are facing a global decline due to ocean warming and eutrophication. In the last decade, with the advent of new technology and molecular advances, there has been a dramatic increase in the number of studies focusing on the effects of ocean warming on seagrasses. Here, we provide a comprehensive review of the future of seagrasses in an era of ocean warming. We have gathered information from published studies to identify potential commonalities in the effects of warming and the responses of seagrasses across four distinct levels: molecular, biochemical/physiological, morphological/population, and ecosystem/planetary. To date, we know that although warming strongly affects seagrasses at all four levels, seagrass responses diverge amongst species, populations, and over depths. Furthermore, warming alters seagrass distribution causing massive die-offs in some seagrass populations, whilst also causing tropicalization and migration of temperate species. In this review, we evaluate the combined effects of ocean warming with other environmental stressors and emphasize the need for multiple-stressor studies to provide a deeper understanding of seagrass resilience. We conclude by discussing the most significant knowledge gaps and future directions for seagrass research.

Abstract. Since the mid-1990s, Australia's Commonwealth Science Industry and Research Organisation (CSIRO) has been developing a biogeochemical (BGC) model for coupling with a hydrodynamic and sediment model for application in estuaries, coastal waters and shelf seas. The suite of coupled models is referred to as the CSIRO Environmental Modelling Suite (EMS) and has been applied at tens of locations around the Australian continent. At a mature point in the BGC model's development, this paper presents a full mathematical description, as well as links to the freely available code and user guide. The mathematical description is structured into processes so that the details of new parameterisations can be easily identified, along with their derivation. In EMS, the underwater light field is simulated by a spectrally resolved optical model that calculates vertical light attenuation from the scattering and absorption of 20+ optically active constituents. The BGC model itself cycles carbon, nitrogen, phosphorous and oxygen through multiple phytoplankton, zooplankton, detritus and dissolved organic and inorganic forms in multiple water column and sediment layers. The water column is dynamically coupled to the sediment to resolve deposition, resuspension and benthic–pelagic biogeochemical fluxes. With a focus on shallow waters, the model also includes detailed representations of benthic plants such as seagrass, macroalgae and coral polyps. A second focus has been on, where possible, the use of geometric derivations of physical limits to constrain ecological rates. This geometric approach generally requires population-based rates to be derived from initially considering the size and shape of individuals. For example, zooplankton grazing considers encounter rates of one predator on a prey field based on summing relative motion of the predator with the prey individuals and the search area; chlorophyll synthesis includes a geometrically derived self-shading term; and the

Seagrasses host an extremely diverse microbiome that plays fundamental roles in seagrass health and productivity but may be sensitive to shifts in host physiology. Here, we observed a leaf reddening phenomenon in Zostera muelleri and characterized bacterial assemblages associated with green and reddened leaves to determine whether this change in leaf pigmentation stimulates shifts in the seagrass microbiome. Using 16S rRNA gene amplicon sequencing, we observed that the microbiome associated with 4 different leaf pigmentation categories (i.e. green, white, purple and black) differed significantly, with substantial changes in microbiome composition when the tissue is whitened (non-pigmented). Actinobacteria, Rhodobacteraceae, Erythrobacter, Sulfitobacter and Granulosicoccus were enriched in black and/or purple tissues and discriminated these microbiomes from those associated with green leaves. Contrastingly, all ‘discriminatory’ zero-radius operational taxonomic units (zOTUs) were depleted within the communities associated with white samples. While 40% of the abundant zOTUs identified were exclusively associated with a single pigmentation category, only 3% were shared across all categories, indicating partitioning of the phyllosphere microbiome. However, a significant proportion of the ‘normal’ (green) leaf core microbiome was also retained in the core communities associated with black (70%) and purple (70%) tissues. Contrastingly, no core zOTUs were maintained in the white tissues. These results indicate that environmentally driven physiological shifts in seagrasses, such as leaf reddening expressed in response to high irradiance, can impact the seagrass leaf microbiome, resulting in significant shifts in the microbiome of reddened leaves with the most extreme expression (in white tissue of reddened

Microalgae exhibit great potential for recombinant therapeutic protein production, due to lower production costs, immunity to human pathogens, and advanced genetic toolkits. However, a fundamental aspect to consider for recombinant biopharmaceutical production is the presence of correct post-translational modifications. Multiple recent studies focusing on glycosylation in microalgae have revealed unique species-specific patterns absent in humans. Glycosylation is particularly important for protein function and is directly responsible for recombinant biopharmaceutical immunogenicity. Therefore, it is necessary to fully characterise this key feature in microalgae before these organisms can be established as industrially relevant microbial biofactories. Here, we review the work done to date on production of recombinant biopharmaceuticals in microalgae, experimental and computational evidence for N- and O-glycosylation in diverse microalgal groups, established approaches for glyco-engineering, and perspectives for their application in microalgal systems. The insights from this review may be applied to future glyco-engineering attempts to humanize recombinant therapeutic proteins and to potentially obtain cheaper, fully functional biopharmaceuticals from microalgae.

© 2020 Elsevier B.V. High rate algal ponds are recognised as a cost effective and efficient upgrade to conventional wastewater ponds for the treatment of a wide range of wastewaters. Their design allows microalgae to proliferate, which, in turn, results in high levels of nutrient removal, via algal assimilation. Furthermore, these ponds offer the opportunity to recover resources, in the form of algal biomass, for beneficial re-use, thus creating a circular bio-economy using wastewater. However, both increased microalgal biomass and nutrient removal is required to make coupled full-scale systems commercially viable. The performance of high rate algal ponds operated in series, on short hydraulic retention time of 4 days, versus in parallel, on a longer retention time of 8 days, was assessed with respect to nutrient removal and microalgal production. For microalgal productivity, the combined total volatile suspended solids (organic matter) and chlorophyll-a biomass were significantly higher (p < 0.01) under Series (191 ± 41 kg per day for volatile suspended solids) than Parallel (127 ± 18 kg per day) operation. The combined total dissolved inorganic nitrogen removed per day was significantly higher (p < 0.01) under Series (23 ± 4 kg of nitrogen per day) than Parallel (17 ± 4 kg) operation. The total amount of phosphorus removed per day was unaffected by mode of operation. Higher biomass production under short retention times came at the expense of nitrogen removal but treatment of the harvested effluent through a second pond in series, resulted in overall higher daily nitrogen removal and biomass production than ponds in parallel, for the same volume of wastewater treated. This study has demonstrated that with simple modifications to pond operation higher microalgal yields and improved effluent water quality without increased capital or operational costs.