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Heterotrophic denitrification using mariculture solid wastes (MSW) fermentation liquid as carbon source is an economically and environmentally sustainable strategy for NO

Taxonomic confusion has been a significant problem with the small species of Gelidium because of their simple and variable morphology. In this study, specimens of two turf-forming species from southern China were studied on the basis of morphology and molecular data. Both data sets revealed the presence of two novel species in Gelidium: G. sanyaense sp. nov. and G. yangmeikengense sp. nov., described here. Gelidium sanyaense, forming sparse or dense turfs along the coast of southern China, was distinguished by the presence of compact brushlike haptera, a flattened and lanceolate axis, simple branches, and sparse medullary cells surrounded by rhizines. Gelidium yangmeikengense was characterized by a broad, stipelike axis that was constricted at the base, broadened in the middle and attenuated upward to become slender and cylindrical, and by sparsely pinnate branches on the upper portion of the axis. In phylogenies of both COI and rbcL sequences, G. sanyaense and G. yangmeikengense were distantly r...

Microalgae can synthesize their own active substances by absorbing nitrogen, phosphorus in wastewater to provide the nourishing bait for the aquatic organisms, when purifying the aquaculture wastewater. This research Thalassiosira pseudonana (Tp) and Isochrysis galbana (Ig) were selected to treat fishery wastewater and then evaluation of their active components. The results showed that the highest biomass productivity of Tp and Ig was 0.11 g·L−1·day−1 and 0.14 g·L−1·day−1, respectively, at the optimal initial inoculum biomass of 0.4 g·L−1. Furthermore, the two strains were co-cultured in different initial inoculum volume ratios, and the highest biomass was at the volume ratio of 1:1. With the most suitable inoculum biomass and volume ratio, the removal rates of NH4+-N, TN and TP were 80.65%, 85.29% and 92.75%, respectively. Moreover, the cells after wastewater treatment showed high contents of carbohydrate, protein, and lipid, which were 36.62%, 8.72% and 23.11%, respectively. This study showed that co-culturing Thalassiosira pseudonana with Isochrysis galbana to treat fishery wastewater is feasible, and algae cells have high nutritional value, which may provide a feasible technology for ecological protection and resource utilization of aquaculture.

Neopyropia yezoensis, an important marine crop, reproduces via sporangial filaments. This special sporophyte stage, which directly releases conchospores—the “seed” of gametophytes (thalli)—is poorly understood. Under free-living culture, we found sporangial filaments varied between hollow cells (at high density) and content-enriched bipartite cells (at low density), released as conchospores. Serious intracellular degradation, which might through fusion of a double-membrane coated body with vacuole, was observed in hollow cells but disappeared in newly-formed bipartite cells and reappeared in their subsequent vegetative growth through transmission electron microscope. The bipartite cells can also return to vegetative growth when not released and the conchospores release was obviously inhibited by some growth promoting conditions such as high light (40–100 μmol photons m−2 s−1) and treatment with ampicillin and streptomycin. Based on these results, we summarized that conchopsore release was inhibited by the vegetative growth of bipartite cells and the cell hollowing caused by vacuole-based intracellular degradation in sporangial filaments. These results would increase understanding of sporangial filament development and conchospores release in N. yezoensis.

The previous study revealed that the mutant strain E thalli of Pyropia yezoensis had growth advantage compared with the initial strain NA, and transcriptome analysis revealed the relevant bioprocesses for improved growth. To investigate the growth mechanism at the protein level, this study used isobaric tags for relative and absolute quantification and liquid chromatography-mass spectrometry to analyze proteome of both strains. In total, 277 proteins were identified, among which 41 differentially expressed proteins were screened, including 22 up-regulated proteins and 19 down-regulated proteins. Integrated analysis of proteome and previous transcriptome showed that the proteins related to photosynthesis, protein biosynthesis, glycolysis, and pentose phosphate pathway were enhanced in mutant strain E, which were supposed to facilitate growth of mutant strain E, and the proteins relevant to stress resistance were up-regulated, which might promote the growth of mutant strain E under abiotic stresses, while proteins related to methylation were decreased, which might enhance the expression of growth relevant genes in mutant strain E. This study revealed the growth mechanism in mutant strain E by integrated omics analysis, and also provided theoretical foundation for molecular breeding of Py. yezoensis.

Dunaliella salina is a unicellular green alga extensively studied due to its capability of salt stress tolerance and high economic value for β-carotene production. Glycerol is synthesized to regulate intracellular osmotic pressure during salt stress in D. salina. In order to demonstrate the electron and reducing power distribution pattern in this process, photosynthetic performance and oxidative pentose phosphate pathway (OPPP) operation during salt stress were investigated. Glycerol was accumulated massively when D. salina was subjected to salt stress. Meanwhile, photosystem II (PSII) activity was increased while photosystem I (PSI) activity was decreased. This suggests that a small portion of the electrons generated in PSII were leaked and were transferred to generate reactive oxygen species (ROS), while most electrons subsequently used to PSI to generate ATP and NADPH. Furthermore, the OPPP was enhanced in order to provide reducing power and carbon skeleton for glycerol synthesis. In conclusion, during salt stress, the imbalance of photosynthetic electron distribution between PSII and PSI in D. salina resulted in a shortage of NADPH and ATP for glycerol biosynthesis, which also led the enhancement of the OPPP and ROS generation.

Heavy metal pollution in aquatic environments is a significant environmental problem. Marine macroalgae are novel materials for the removal of heavy metals from water, aided by their large biomass and the feature of easy collection. In this study, Ulva prolifera O.F.Muller was used to remove cadmium ions (Cd2+) from the aquatic environment. We examined the Cd2+ absorption capacity of the thalli in a factorial experiment using fresh thalli cultivated in seawater, freshwater, water containing domestic garbage, water containing industrial waste and elutriant of soil with additional Cd2+. In addition, changes in photosynthetic activity of thalli were investigated. A significant decrease of maximum quantum yield and effective photochemical quantum yield of PSII (YII) indicated Cd2+ was transported into the cells and seriously inhibited photosynthesis. Furthermore, the Cd2+ absorption capacity was relatively high. The results indicated the suitability of U. prolifera for removing Cd2+ from aquatic environments of different backgrounds.

Pyropia haitanensis has prominent stress-resistance characteristics and is endemic to China. Studies into the stress responses in these algae could provide valuable information on the stress-response mechanisms in the intertidal Rhodophyta. Here, the effects of salinity and light intensity on the quantum yield of photosystem II in Py. haitanensis were investigated using pulse-amplitude-modulation fluorometry. Total RNA and genomic DNA of the samples under different stress conditions were isolated. By normalizing to the genomic DNA quantity, the RNA content in each sample was evaluated. The cDNA was synthesized and the expression levels of seven potential internal control genes were evaluated using qRT-PCR method. Then, we used geNorm, a common statistical algorithm, to analyze the qRT-PCR data of seven reference genes. Potential genes that may constantly be expressed under different conditions were selected, and these genes showed stable expression levels in samples under a salinity treatment, while tubulin, glyceraldehyde-3-phosphate dehydrogenase and actin showed stability in samples stressed by strong light. Based on the results of the pulse amplitude-modulation fluorometry, an absolute quantification was performed to obtain gene copy numbers in certain stress-treated samples. The stably expressed genes as determined by the absolute quantification in certain samples conformed to the results of the geNorm screening. Based on the results of the software analysis and absolute quantification, we proposed that elongation factor 3 and 18S ribosomal RNA could be used as internal control genes when the Py. haitanensis blades were subjected to salinity stress, and that α-tubulin and 18S ribosomal RNA could be used as the internal control genes when the stress was from strong light. In general, our findings provide a convenient reference for the selection of internal control genes when designing experiments related to stress responses in Py. haitanensis.

The taxonomic relationship of Chinese Gelidium tsengii and Gelidium johnstonii was ambiguous. For almost 20 years they have been regarded as distinct taxa and until 2002 G. johnstonii was considered as a misapplied name of G. tsengii. In this study, herbarium specimens that initially attributed to G. tsengii and fresh G. tsengii specimens were used to address the taxonomic issues. In phylogenetic studies, G. tsengii from Dayawan, China, near the type locality of G. tsengii and G. johnstonii from Sonora, Mexico, the type locality of G. johnstonii, formed a monophyletic group with maximum support in rbcL and COI genes analyses, indicating that they were genetically identical. In morphological studies, G. tsengii was similar to G. johnstonii in branching pattern, inner structures and fructiferous organs. Consequently, we considered that semi-circular outline of G. tsengii could no longer be treated as a discrimating feature. G. johnstonii had priority of publication and according to the International Code of Botanical Nomenclature, G. tsengii was proposed as a synonym of G. johnstonii. Gelidium honghaiwanense sp. nov. was described from Guangdong, China on the basis of morphological and molecular data. For vegetative structures, it was characterized by flattened upright frond, regular two-three times branches pinnate or alternate and clavate ultimate branchlets. For reproductive structures, the tetrasporangial sori were in the apical part of branches and the tetrasporangial branchlets were distichously distributed along second order branches. The present study clarified the relationship between G. tsengii and G. johnstonii from Guangdong and added a new Gelidium species to the Chinese algal flora.

Background Numerous studies have shown that stress induction and genetic engineering can effectively increase lipid accumulation, but lead to a decrease of growth in the majority of microalgae. We previously found that elevated CO2 concentration increased lipid productivity as well as growth in Phaeodactylum tricornutum, along with an enhancement of the oxidative pentose phosphate pathway (OPPP) activity. The purpose of this work directed toward the verification of the critical role of glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme in the OPPP, in lipid accumulation in P. tricornutum and its simultaneous rapid growth rate under high-CO2 (0.15%) cultivation. Results In this study, G6PDH was identified as a target for algal strain improvement, wherein G6PDH gene was successfully overexpressed and antisense knockdown in P. tricornutum, and systematic comparisons of the photosynthesis performance, algal growth, lipid content, fatty acid profiles, NADPH production, G6PDH activity and transcriptional abundance were performed. The results showed that, due to the enhanced G6PDH activity, transcriptional abundance and NAPDH production, overexpression of G6PDH accompanied by high-CO2 cultivation resulted in a much higher of both lipid content and growth in P. tricornutum, while knockdown of G6PDH greatly decreased algal growth as well as lipid accumulation. In addition, the total proportions of saturated and unsaturated fatty acid, especially the polyunsaturated fatty acid eicosapentaenoic acid (EPA; C20:5, n-3), were highly increased in high-CO2 cultivated G6PDH overexpressed strains. Conclusions The successful of overexpression and antisense knockdown of G6PDH well demonstrated the positive influence of G6PDH on algal growth and lipid accumulation in P. tricornutum. The improvement of algal growth, lipid content as well as polyunsaturated fatty acids in high-CO2 cultivated G6PDH overexpressed P. tricornutum suggested this G6PDH overexpression-high CO2 cultivation pattern provides an efficient and economical route for algal strain improvement to develop algal-based biodiesel production.

Non-photochemical quenching (NPQ) is an important photoprotective mechanism in plants, which dissipates excess energy and further protects the photosynthetic apparatus under high light stress. NPQ can be dissected into a number of components: qE, qZ, and qI. In general, NPQ is catalyzed by two independent mechanisms, with the faster-activated quenching catalyzed by the monomeric light-harvesting complex (LHCII) proteins and the slowly activated quenching catalyzed by LHCII trimers, both processes depending on zeaxanthin but to different extent. Here, we studied the NPQ of the intertidal green macroalga, Ulva prolifera, and found that the NPQ of U. prolifera lack the faster-activated quenching, and showed much greater sensitivity to dithiothreitol (DTT) than to dicyclohexylcarbodiimide (DCCD). Further results suggested that the monomeric LHC proteins in U. prolifera included only CP29 and CP26, but lacked CP24, unlike Arabidopsis thaliana and the moss Physcomitrella patens. Moreover, the expression levels of CP26 increased significantly following exposure to high light, but the concentrations of the two important photoprotective proteins (PsbS and light-harvesting complex stress-related [LhcSR]) did not change upon the same conditions. Analysis of the xanthophyll cycle pigments showed that, upon exposure to high light, zeaxanthin synthesis in U. prolifera was gradual and much slower than that in P. patens, and could effectively be inhibited by DTT. Based on these results, we speculate the enhancement of CP26 and slow zeaxanthin accumulation provide an atypical NPQ, making this green macroalga well adapted to the intertidal environments.

Additional file 1: Table S1. List of primers used in this study.

The effects of heat pretreatment on waste sludge hydrolysis were investigated in this study. Heat pretreatment was conducted at 65°C, 80°C, 100°C and 121°C for 5min, 10min, 15min, 20min, 25min and 30min. Not only analyzed the changes of SCOD (Soluble chemical oxygen demand), carbohydrate and protein, but also evaluated the structural and functional properties of organics in extracellular polymeric substances (EPS) and dissolved organic matters (DOM) by using three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy with fluorescence regional integration (FRI) analysis. The SCOD in DOM increased with pretreated temperatures. The optimal heat hydrolysis temperature and time were selected by further studying the biodegradable and non-biodegradable components. After treated at 80°C for 25min, the fluorescence intensity and percent fluorescence response (Pi,n) of easily biodegradable soluble microbial by-product substance were higher than others, and little non-biodegradable fulvic acid-like substance was accumulated.

Free-floating Ulva prolifera is one of the causative species of green tides. When green tides occur, massive mats of floating U. prolifera thalli accumulate rapidly in surface waters with daily growth rates as high as 56%. The upper thalli of the mats experience environmental changes such as the change in carbon source, high salinity, and desiccation. In this study, the photosynthetic performances of PSI and PSII in U. prolifera thalli exposed to different atmospheric carbon dioxide (CO2 ) levels were measured. Changes in photosynthesis within salinity treatments and dehydration under different CO2 concentrations were also analyzed. The results showed that PSII activity was enhanced as CO2 increased, suggesting that CO2 assimilation was enhanced and U. prolifera thalli can utilize CO2 in the atmosphere directly, even when under moderate stress. In addition, changes in the proteome of U. prolifera in response to salt stress were investigated. Stress-tolerance proteins appeared to have an important role in the response to salinity stress, whereas the abundance of proteins related to metabolism showed no significant change under low salinity treatments. These findings may be one of the main reasons for the extremely high growth rate of free-floating U. prolifera when green tides occur.

Sargassum fusiforme, a species of brown seaweed with economic importance, inhabits lower intertidal zones where algae are often exposed to various stresses. In this study, changes in the photosynthetic performance of S. fusiforme under saline stress were investigated. The PSII performance in S. fusiforme significantly improved, when the thalli were exposed to 0% salinity, and remained high with prolonging treatment time. In contrast, the PSII activity declined considerably under salinities of 4.5 and 6%. The PSI activity did not change remarkably under saline stress, thus demonstrating higher tolerance to saline stress than PSII. In addition, the PSI activity could be also restored after saline treatments, when PSII was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. It might be as a result of changes in the NAD(P)H content in the thalli under saline stress. Our results suggested that PSI was much more tolerant to different saline stress than PSII in S. fusiforme. We demonstrated that S. fusiforme was much more tolerant to hyposaline than to hypersaline stress.

Microalgae are rich in various high-value compounds and thus have been proposed for use in biodiesel production and other industrial processes. Mixotrophy of microalgae can generate a high biomass and a high cell content of desirable compounds. To elucidate the probable relationship between pH drift, carbon source utilization, light intensity, and biomass accumulation in Chlorella cultivation, we compared the growth, pH drift, total biomass, and lipid and starch contents of Chlorella sorokiniana GXNN01 under different culture conditions. We also labeled the cell with 13C-labeled substrates. The results of pH drift and 13C labeling showed that Chlorella preferred acetate under high light, but glucose under low light. Glucose utilization resulted in decrease of pH, while acetate had the opposite effect. A combination of acetic acid and glucose as carbon source maintained the pH close to the initial value and significantly increased total biomass production. Cultures using acetic acid as carbon source or addition of sodium acetate under low light appeared to enhance total lipid content, while pH adjustment, addition of two carbon sources, or addition of sodium acetate under normal light (20 μmol photons m−2 s−1) resulted in high starch content. This knowledge will guide future Chlorella cultivation.

Gracilaria spp. are dominant macroalgae inhabiting the intertidal zone and are exposed to constant wave action and currents. In wild Gracilaria populations, fronds tend to occur in clusters, being grouped close to one another on the shore. It is rare to find thalli growing individually, but the reason for such a clustering development is unknown. In this study we traced the early development of tetraspores of Gracilaria sp. and examined the adhesion strength of discs. We recorded two different tetraspore-derived disc developmental patterns: in the first pattern, individual tetraspores developed into discs; whereas in the second pattern, multiple tetraspores that had attached in proximity to each other, coalesced to form a single composite disc during early development. We found that more uprights grew from coalesced discs and that the attachment areas of coalesced discs were larger compared with those of individual discs. The adhesion strengths of coalesced discs and individual discs were analyzed. The retention percentage of coalesced discs after treatment with rapid water flow was higher than that of individual discs, suggesting that coalesced discs are better able to withstand wave flow when compared with single-spore discs. Based on these results, we propose that the clustering of Gracilaria sp. plants at sites within the intertidal zone is a mechanism that enables this macroalgae to survive the wave action and currents that occur in this zone, and that plant recruitment in these areas is enhanced by the coalescence of holdfast discs during early development.

Photoprotection mechanisms protect photosynthetic organisms, especially under stress conditions, against photodamage that may inhibit photosynthesis. We investigated the effects of short-term immersion in hypo- and hypersalinity sea water on the photosynthesis and xanthophyll cycle in Sargassum fusiforme (Harvey) Setchell. The results indicated that under moderate light [110 mu mol(photon) m(-2) s(-1)], the effective quantum yield of PSII was not reduced in S. fusiforme fronds after 1 h in hyposalinity conditions, even in fresh water, but it was significantly affected by extreme hypersalinity treatment (90aEuro degrees sea water). Under high light [HL, 800 mu mol(photon) m(-2) s(-1)], photoprotective mechanisms operated efficiently in fronds immersed in fresh water as indicated by high reversible nonphotochemical quenching of chlorophyll fluorescence (NPQ) and de-epoxidation state; the quantum yield of PSII recovered during the subsequent relaxation period. In contrast, fronds immersed in 90aEuro degrees sea water did not withstand HL, barely developed reversible NPQ, and accumulated little antheraxanthin and zeaxanthin during HL, while recovery of the quantum yield of PSII was severely inhibited during the subsequent relaxation period. The data provided concrete evidence supporting the short-term tolerance of S. fusiforme to immersion in fresh water compared to hypersalinity conditions. The potential practical implications of these results were also discussed.

A marine photosynthetic bacterial strain LC83 was isolated from bathing beach sludge and identified as Marichromatium purpuratum using light microscopic examination, Biolog tests, and 16S rRNA gene sequence analysis. The strain is a salt- and alkali-tolerant, vitamin independent facultative anaerobe with an optimum sodium chloride (NaCl) concentration of 30 parts per thousand, initial optimum pH of 7.0-8.0, optimum temperature of 30 degrees C, and optimum light intensity of 80-160 mu mol/m(2)/s. The addition of M. purpuratum LC83 to the dark fermentation of Pantoea agglomerans BH-18 for 8 h clearly improved the pH and the oxidation-reduction potential of the fermentative liquid, retarded the reduction in glucose, and maintained the balance between the glucose generated photosynthetically by the photosynthetic bacteria and those consumed by the fermentative bacteria in the early stage of coupled fermentation. The addition of photosynthetic bacteria to dark fermentation at 8 h improved the fermentative liquid conditions in favor of hydrogen production. The yield of hydrogen and the amount of glucose consumed by the coupled fermentation were also both higher than during pure fermentation by P. agglomerans BH-18. The optimum inoculation ratio was 1/8 (strains BH-18/LC83). The coupled dark and photofermentation of M. purpuratum LC83 and P. agglomerans BH-18 is a feasible way of improving the level of hydrogen produced in marine culture. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Mechanisms for carbon fixation via photosynthesis in the diatom Phaeodactylum tricornutum Bohlin were studied recently but there remains a long-standing debate concerning the occurrence of C4 photosynthesis in this species. A thorough investigation of carbon metabolism and the evidence for C4 photosynthesis based on organelle partitioning was needed.In this study, we identified the flux ratios between C3 and C4 compounds in P. tricornutum using (13)C-labelling metabolic flux ratio analysis, and stained cells with various cell-permeant fluorescent probes to investigate the likely organelle partitioning required for single-cell C4 photosynthesis. Metabolic flux ratio analysis indicated the C3/C4 exchange ratios were high. Cell staining indicated organelle partitioning required for single-cell C4 photosynthesis might exist in P. tricornutum.The results of (13)C-labelling metabolic flux ratio analysis and cell staining suggest single-cell C4 photosynthesis exists in P. tricornutum.This study provides insights into photosynthesis patterns of P. tricornutum and the evidence for C4 photosynthesis based on (13)C-labelling metabolic flux ratio analysis and organelle partitioning.

Batch tests of cultivations were conducted to analyze influences of pre-treatment methods (heat-shock, acid, and alkaline) on hydrogen production. The hydrogen yields of the pre-treated samples were significantly higher than those without pre-treatment. Heat-shock pre-treatment yielded maximum hydrogen (75.5 +/- 4.0 mL/g sucrose(removed)), and had the highest sucrose removal efficiency (81.20 +/- 1.23%). Heat-shock pre-treatment produced more ethanol and acetate (80.44 +/- 0.55% of the total soluble metabolites), which belonged to ethanol-type fermentation. Denaturing gradient gel electrophoresis (DGGE) profiles showed that pre-treatment methods affected the composition of microbial communities. The results showed that pre-treatment methods play a key role in the hydrogen production process of marine hydrogen-producing microflora.

The increase in atmospheric CO2 and acid rain precipitation are serious global environmental problems that have had worldwide consequences, including the damage of biodiversity in intertidal zones. The decline in species richness in the intertidal zone of Wenzhou, China, is a typical example. In this study, we investigated the effects of CO2-enriched seawater, CO2-enriched air and acid rain on a dominant species, Corallina sp., and an inferior species, Ulva conglobata, in the intertidal zone of Wenzhou. The responses of Corallina sp. and U. conglobata to high-CO2 seawater are similar, demonstrating that both of them are tolerant of seawater acidification induced by aerating CO2-enriched air. The PSII activities of Corallina sp. declined markedly when exposed to CO2-free air, while they increased significantly with high-CO2 air. An increase of non-photochemical quenching (NPQ) was induced by CO2-free air, but it declined remarkably with CO2-enriched air, suggesting that Corallina sp. can use atmospheric CO2 as carbon source for photosynthesis. Corallina sp. survived extremely low pH conditions (pH 3) and could regulate the pH of their ambient seawater through the dissolution of CaCO3, while the photosynthetic properties of U. conglobata decreased drastically and even the thalli were damaged irreversibly under low pH conditions (pH 3). These results suggest that Corallina sp. is much more tolerant of extremely low pH than U. conglobata. Based on these results, we suggest that it is not the increase of atmospheric CO2 but acid rain at least in part contributed to the damage of the biodiversity in the intertidal zone, with the result that these areas are now mainly dominated by Corallina sp. (C) 2015 Elsevier B.V. All rights reserved.

Although biotechnologies for astaxanthin production from Haematococcus pluvialis have been developed for decades and many production facilities have been established throughout the world, the production cost is still high. This paper is to evaluate the current production processes and production facilities, to analyze the R&D strategies for process improvement, and to review the recent research advances shedding light on production cost reduction. With these efforts being made, we intent to conclude that the production cost of astaxanthin from Haematococcus might be substantially reduced to the levels comparable to that of chemical astaxanthin through further R&D and the future research might need to focus on strain selection and improvement, cultivation process optimization, innovation of cultivation methodologies, and revolution of extraction technologies.

With depletion of fossil fuel, microalgae is considered as a promising substitute due to high growth rate, efficient cost and high biofuels content. This study investigated the effect of temperature on mixotrophic cultivation of Chlorella vulgaris. In addition, the combination carbon source of inorganic (HCO3- or CO32-) and organic (glucose or acetate) for microalgae cultivation was evaluated to obtain the optimum carbon source for mixotrophic cultivation. The results showed that the optimum temperature of microalgae cultivation was at the range of 15 - 20 °C. The activity of Rubisco was obviously inhibited at the temperature of 30 °C, however, citrate synthase was not susceptible to the increasing temperature. COD removal efficiency was all higher than 64.0%. Low temperature was benefit for protein formation, and the lipid accumulation occurred at high temperature. The results provide a fresh perspective between enzyme activity and temperature variation for product accumulation of microalgae.

The red alga Pyropia yezoensis is an economically important marine crop whose life cycle includes two distinct stages: conchocelis and blades. These two types of thalli live in significantly different environments and have distinct shapes and physiological features. The photosynthetic apparatus of red algae, especially the light harvesting antenna, is unique. However, little is known about the photosynthetic apparatus of P. yezoensis. We studied the composition and organization of thylakoid membranes in conchocelis and blades of P. yezoensis and found that the photosynthetic complexes differed between the two stages. Conchocelis had much higher photosystem I (PSI)/ photosystem II and PSI/Cytochrome b6/f ratios compared with blades. Additionally, a macromolecular protein complex that bound with lutein and Chlorophyll a was detected in conchocelis but not in blades. The number and types of light harvesting complex subunits associated with PSI and the corresponding pigment binding also varied between conchocelis and blades. These differences are an important strategy that allows the two P. yezoensis stages to adapt to various environments.

Pyropia yezoensis (P. yezoensis) is an intertidal alga that periodically experiences environmental stress with turning tides. Both the antioxidases and the antioxidants are involved in the acclimation to the extremely variable intertidal environments. Here, mild (50‰), moderate (90‰), and severe (120‰) high-salinity stress treatments were designed to investigate protective mechanisms against reactive oxygen species (ROS). Results showed that hydrogen peroxide (H2O2) content in high-salinity stressed samples was maintained at levels similar to or lower than that of the control. Superoxide dismutase (SOD) activity was up-regulated in samples treated with severe high-salinity and sustained stress with moderate high-salinity. Catalase (CAT) activity increased at the start of the experiment but decreased after 2 h of stress treatment. Reduced ascorbate (AsA) was up-regulated under high-salinity conditions, and AsA-dependent antioxidant enzymes played a more important role in the mild and moderate high-salinity stress treatments. While, reduced glutathione (GSH)-mediated antioxidant reactions became the most important as salinity increased to 120‰. Moreover, the rapid glutathione up-regulation during the initial stage of stress treatments demonstrated that GSH is essential in the scavenging of instantaneous ROS bursts. GSH was also suggested to be a central intermediate molecule involved in multiple oxidative stress response pathways. The results obtained here will do benefits to the breeding of P. yezoensis.

This study investigated the large-scale use of the red macroalga Gracilaria tenuistipitata to extract partially purified R-phycoerythrin in combination with the sequential extraction of agar. The main objective was to investigate the purification of R-PE, the extraction of agar and treatment of wastewater from the whole extraction process using the green macroalga Ulva prolifera. Results showed that the processing of 1 kg fresh biomass of G. tenuistipitata yielded a 30.34 μg/g R-phycoerythrin (purification ratio > 4) with 13.83% extraction efficiency. Initial phycobiliprotein extraction had no effect on the agar yield. The physicochemical properties of the agar had industrial applications. This method of extraction reduced the water volume and alkali requirement compared with that from direct extraction from algae. In addition, the removal rates (mean ± standard deviation) from wastewater of BOD, COD, total nitrogen, inorganic nitrogen, ammonia nitrogen, nitrate, nitrite, total phosphorus and inorganic phosphorus were 28.34 ± 0.10%, 23.50 ± 3.47%, 45.59 ± 6.31%, 63.82 ± 2.94%, 40.77 ± 0.95%, 74.06 ± 5.63%, 70.37 ± 2.59%, 65.26 ± 5.77%, and 72.40 ± 5.43% after the treatment with 2 days respectively. This extraction and subsequently eco-friendly wastewater treatment method could have practical application in the agar industry.

Heterotrophic denitrification using mariculture solid wastes (MSW) fermentation liquid as carbon source is an economically and environmentally sustainable strategy for NO3−-N removal in marine recycling aquaculture systems (RAS). The optimization of COD/NO3−-N ratio (C/N) and hydraulic retention times (HRT) with respect to MSW fermentation liquid driven denitrification for marine RAS wastewater treatment was investigated. The optimum C/N of 8 and HRT of 6 h for heterotrophic denitrification was obtained with NO3−-N removal efficiency of 97.8% and 94.2%, respectively. Using MSW fermentation liquid as carbon source, the utilization of VFAs was more effective than that of carbohydrates and proteins, and effluent COD concentration decreased with an increment in HRT from 4 to 8 h. The results of high-throughput sequencing analysis showed microbial communities were enriched selectively in the reactors by optimizing C/N and HRT, which obviously enhanced the nitrogen removal in respect to MSW fermentation liquid driven denitrification.

Light drives photosynthesis but may also cause photodamage. Oxygenic photosynthetic organisms have evolved various photoprotective responses to adapt to excessive light. Zeaxanthin and its precursor, β-carotene, play key photoprotective roles in higher plants and in most algae; however, it remains unclear if they are also involved in photoprotective responses in red algae. Here, we report that the concentrations of β-carotene and zeaxanthin increased significantly in response to high light conditions in Pyropia yezoensis (Bangiales, Rhodophyta) sporophytes. However, the response was relatively minor, and the accumulated zeaxanthin did not reduce when the stress was eliminated. The accumulation of β-carotene and zeaxanthin in P. yezoensis was accompanied with variations in non-photochemical quenching kinetics when the sporophytes were subjected to high light stress. We cloned the cDNAs encoding lycopene ϵ-cyclase and β-carotene hydroxylase in P. yezoensis, and quantified their expression levels. Our results suggested that the accumulation of β-carotene and zeaxanthin was attributed to the reduced expression levels of lycopene ϵ-cyclase and increased expression levels of β-carotene hydroxylase. Therefore, we propose that although red algae have evolved a common response to high light stress by accumulating β-carotene and zeaxanthin, the mechanism is not as flexible as in higher plants and other algae using the xanthophyll cycle. Rather than binding to PSII as in higher plants and other algae, the accumulated zeaxanthin may bind to PSI-light harvesting complex I in P. yezoensis, and in turn protect PSI against high light-induced photodamage.

Ulva sp. is a large intertidal species of green algae that has been a causative species in green tide in the Qingdao sea area of China since 2008. To explore the physiological basis of outbreaks, we investigated the photosynthetic carbon sequestration mechanism of Ulva sp. Growth and breeding capacity, chlorophyll fluorescence parameters, chlorophyll content, and enzyme activities of carbonic anhydrase and other important enzymes in the C4 pathway were measured when different inorganic carbon sources were provided (0, 400, 1500, 20,000 μL·L−1 of CO2 or HCO3−). When CO2 was absent (0 μL·L−1 CO2), chlorophyll fluorescence parameters [Fv/Fm, Y (II), Y(I)] and chlorophyll content decreased significantly, but NPQ parameters and MDH and PEPC enzyme activities increased significantly and PEPCK enzyme activity was not affected significantly. When HCO3− was added, chlorophyll content and NAD-ME enzyme activity decreased significantly. These results indicated that lack of CO2 could stimulate photoprotection of Ulva sp. containing decreasing the synthesis of chlorophyll and reducing the PSII reaction center of the open state. Ulva sp. may not have the PEPCK C4 type CCM and might use the NAD-ME C4 type CCM to tolerate the stress caused by the lack of CO2.

China is rich in seaweed resources and is currently the largest seaweed producer in the world. The current study identified and investigated the geographical distribution of economically important red seaweed species around the Chinese coast, all of which are potential candidates for development in the seaweed farming industry. The study also highlighted progress made in research related to red seaweed farming in China. Farming of Pyropia and Gracilaria species continues to show steady growth, although with the occasional emergence of biological or ecological stresses. However, farming of eucheumatoid species is facing challenges because of devastating diseases and, therefore, we propose that the ‘seedling problem’ is a major obstacle in the cultivation of agarophytes and carrageenanophytes. Integrated multitrophic aquaculture systems and modern marine ranching represent the future direction of the aquaculture industry, represented by high outputs and ecologically friendly processes; seaweed farming is also likely to be able to supply feedstock for the future production of bioactive compounds and bioethanol. Overall, the utilization of red seaweeds in China is converting from traditional scattered domestic uses to modern large-scale commercial uses; thus, such high-efficiency and high-value utilization represent the future for red seaweeds in China.

The attachment of Ulva prolifera to Pyropia rafts can cause severe economic losses during the cultivation of Pyropia because it can reduce the yield, harvest, and quality of the Pyropia. The existing methods for removing U. prolifera from the Pyropia raft have many limitations, such as low removal efficiency, Pyropia damage, and environmental pollution. In this study, we developed method that can effectively remove U. prolifera attached to the raft during Pyropia cultivation. After 3 h of citric acid (pH 4.0) and high light treatment (1200 μmol photons m2− s1−), followed by recovery in seawater for 24 h, the U. prolifera was completely dead, but the Pyropia was still active. We also studied the response mechanism of U. prolifera to acid and high light, and our results showed that under acidic and high light conditions, H+ may penetrate the interior of U. prolifera cells, causing obvious synergistic injury with high light to PSII in U. prolifera. The degradation of Cyt f in this process severely hindered electron transport and slightly reduced PSI activity. Acid also destroyed the U. prolifera photoprotective mechanism, as shown by the high non-photochemical quenching (NPQ) values and xanthophyll cycle pigment contents. This study provides a solid base for further research on optimizing the treatment of U. prolifera and improving its removal efficiency.

Several previous studies have demonstrated the excellent antioxidant activity of fucoxanthin against oxidative stress which is closely related to the pathogenesis of liver diseases. The present work was to investigate whether fucoxanthin could protect human hepatic L02 cells against hydrogen peroxide- (H2O2-) induced oxidative damage. Its effects on H2O2-induced cell viability, lactate dehydrogenase (LDH) leakage, intracellular reduced glutathione, and reactive oxygen species (ROS) contents, along with mRNA and protein relative levels of the cytoprotective genes including Nrf2, HO-1, and NQO1, were investigated. The results showed that fucoxanthin could upregulate the mRNA and protein levels of the cytoprotective genes and promote the nuclear translocation of Nrf2, which could be inhibited by the PI3K inhibitor of LY294002. Pretreatment of fucoxanthin resulted in decreased LDH leakage and intracellular ROS content but enhanced intracellular reduced glutathione. Interestingly, pretreatment using fucoxanthin protected against the oxidative damage in a nonconcentration-dependent manner, with fucoxanthin of 5 μM demonstrating the optimal effects. The results suggest that fucoxanthin exerts cytoprotective effects against H2O2-induced oxidative damage in L02 cells, which may be through the PI3K-dependent activation of Nrf2 signaling.

Background Red algae are economically valuable for food and in industry. However, their genomic information is limited, and the genomic data of only a few species of red algae have been sequenced and deposited recently. In this study, we annotated a draft genome of the macroalga Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta). Results The entire 88.98 Mb genome of Gp. lemaneiformis 981 was generated from 13,825 scaffolds (≥500 bp) with an N50 length of 30,590 bp, accounting for approximately 91% of this algal genome. A total of 38.73 Mb of scaffold sequences were repetitive, and 9281 protein-coding genes were predicted. A phylogenomic analysis of 20 genomes revealed the relationship among the Chromalveolata, Rhodophyta, Chlorophyta and higher plants. Homology analysis indicated phylogenetic proximity between Gp. lemaneiformis and Chondrus crispus. The number of enzymes related to the metabolism of carbohydrates, including agar, glycoside hydrolases, glycosyltransferases, was abundant. In addition, signaling pathways associated with phytohormones such as auxin, salicylic acid and jasmonates are reported for the first time for this alga. Conclusion We sequenced and analyzed a draft genome of the red alga Gp. lemaneiformis, and revealed its carbohydrate metabolism and phytohormone signaling characteristics. This work will be helpful in research on the functional and comparative genomics of the order Gracilariales and will enrich the genomic information on marine algae. Electronic supplementary material The online version of this article (10.1186/s12870-018-1309-2) contains supplementary material, which is available to authorized users.

Table S8. The enzymes related to salicylic acid signaling in Gp. lemaneiformis. (DOCX 25 kb)

Table S1. Comparison of the number of enzymes involved in agar synthesis in the 6 species. (DOCX 26 kb)

Table S4. The numbers of glycosyltransferases (GTs) identified in the Gp. lemaneiformis, C. crispus and S. japonica genomes. (DOCX 26 kb)

Table S7. The genes related to abscisic acid signaling in Gp. lemaneiformis. (DOCX 24 kb)

Table S2. The enzymes involved in converting the agar precursor into agar in Gp. lemaneiformis. (DOCX 24 kb)

Table S5. The enzymes involved in trehalose metabolism. (DOCX 24 kb)

Table S6. The genes related to auxin signaling in Gp. lemaneiformis. (DOCX 24 kb)

Figure S1. The phylogenetic relationship of cellulose synthase (CESA) in Gp. lemaneiformis with those of other related species. The tree was constructed based on the maximum likelihood method with 1000 bootstrap replicates using Mega5.10 software. (DOCX 27 kb)

Flocculation harvesting of the fucoxanthin-rich marine microalga Isochrysis galbana has received little attention. Therefore, we attempted to screen for an optimal chemical flocculant and optimize flocculation conditions from five chemical flocculants-ferric chloride (FC), aluminum sulfate (AS), polyaluminum chloride (PAC), aluminum potassium sulfate (APS), and zinc sulfate (ZS)-for effective flocculation of I. galbana. The growth rate, photosynthetic performance, and fucoxanthin content were determined in re-suspended flocculated algal cells and in the flocculation supernatant cultured algal cells. The results showed that high growth rate and fucoxanthin accumulation were observed when FC was used as the flocculant in I. galbana cultures, which indicated that FC may cause less harm to I. galbana than the other aluminum-based flocculants. Furthermore, satisfactory flocculation efficiency was also observed when FC was used to flocculate I. galbana, and the FC dosage was less than that required for flocculation of I. galbana using PAC, APS, and AS. Thus, we selected FC as the optimal flocculant for harvesting I. galbana based on its flocculation efficiency together with algal physiological performance, growth rate, and fucoxanthin content.

Pyropia yezoensis, belongs to the genus of Porphyra before 2011, inhabit on intertidal zone rocks where irradiation changes dramatically, implying that the seaweed has gained certain mechanisms to survive a harsh environment. Based on the photosynthetic parameters with or without the inhibitors determined by a Dual-PAM-100 apparatus, we investigated the photosynthetic performance and the changes in electron flow that occurred during the algae were stressed with different light intensities previously. When the irradiation saturation was approaching, the CEF around PS I became crucial since the addition of inhibitors usually led to an increase in non-photochemical quenching. The inhibitor experiments showed that there were at least three different CEF pathways in Py. yezoensis and these pathways compensated each other. In addition to maintaining a proper ratio of ATP/NAD(P)H to support efficient photosynthesis, the potential roles of CEF might also include the regulation of different photoprotective mechanisms in Py. yezoensis. Under the regulation of CEF, chlororespiration is thought to transport electrons from the reduced plastoquinone (PQ) pool to oxygen in order to mitigate the reduction in the electron transfer chain. When irradiation was up to the high-grade stress conditions, the relative value of CEF began to decrease, which implied that the NADP+ pool or PQ+ pool was very small and that the electrons were transferred from reduced PS I to oxygen. The scavenging enzymes might be activated and the water-water cycle probably became an effective means of removing the active oxygen produced by the irradiation stressed Py. yezoensis. We believe that the different mechanisms could make up the photoprotective network to allow Py. yezoensis for survival in a highly variable light stress habitat, which may enlighten scientists in future studies on irradiance stress in other algae species.

Crocetin is one of the major active ingredients of the rare medicinal herb saffron (Crocus sativus L.), also known as crocus. Crocetin has a wide range of effects including antitumor, anticancer, antioxidant, and antiatherosclerotic activity. Crocetin is currently only obtained via extraction from crocus stigmas, with limited yields. This study developed a new method of production of crocetin from genetically engineered Chlorella vulgaris, a unicellular, fast-growing, and heterotrophically cultured green microalga. A plant expression vector carrying the genes crtRB and ZCD1, which encode enzymes controlling critical steps in crocetin biosynthesis, was introduced into C. vulgaris using the Agrobacterium tumefaciens-mediated transformation method. After hygromycin screening, resistant C. vulgaris strains were achieved. Polymerase chain reaction amplification confirmed that the crtRB and ZCD1 were successfully integrated into the C. vulgaris genome. High-performance liquid chromatography analysis of methanol extraction showed that the transgenic C. vulgaris was able to produce crocetin, while wild-type C. vulgaris was not. These results strongly suggest that introducing crtRB and ZCD1 into C. vulgaris can successfully produce crocetin. This is a new method of crocetin production in C. vulgaris to compensate for the shortage of crocetin.

The cell wall and cytoplasmic membrane components of algal biomass (in cyanobacterial blooms) are resistant to biodegradation during anaerobic digestion. Various pretreatment methods including thermal, alkaline and acid pretreatments, were performed (each as a two-stage process) to increase the biodegradability of the algal biomass in terms of hydrogen and polyhydroxybutyrate (PHB) production. Among the pretreatment methods, thermal pretreatment achieved the highest hydrogen production (113 mL/g VS), followed by alkaline pretreatment (94 mL/g VS). Following hydrogen production, phototrophic bacteria were inoculated into the fermentative broth, for PHB production. The group that had undergone alkaline pretreatment produced the highest amount of PHB (about 1.69 g/L). Our studies indicate that pretreatment is a feasible option for transforming algal biomass into a bio-available material, for the purpose of microbial hydrogen production and PHB conversion. (C) 2015 Elsevier B. V. All rights reserved.

Pyropia haitanensis (T. J. Chang et B. F. Zheng) N. Kikuchi et M. Miyata (Porphyra haitanensis) is an economically important genus that is cultured widely in China. P. haitanensis is cultured on a larger scale than Pyropia yezoensis, making up an important part of the total production of cultivated Pyropia in China. However, the majority of molecular mechanisms underlying the physiological processes of P. haitanensis remain unknown. P. haitanensis could utilize inorganic carbon and the sporophytes of P. haitanensis might possess a PCK-type C4-like carbon-fixation pathway. To identify microRNAs and their probable roles in sporophyte and gametophyte development, we constructed and sequenced small RNA libraries from sporophytes and gametophytes of P. haitanensis. Five microRNAs were identified that shared no sequence homology with known microRNAs. Our results indicated that P. haitanensis might posses a complex sRNA processing system in which the novel microRNAs act as important regulators of the development of different generations of P. haitanensis.

Malate dehydrogenase (MDH) is an enzyme that catalyzes the interconversion of malate and oxaloacetate substrates and is widely distributed from prokaryotes to eukaryotes. It plays crucial roles in many important metabolic pathways and includes different isoforms based on coenzyme specificity and cellular localization. To study MDH in rhodophytes, we obtained a full-length cDNA clone (here designated PhMDH) encoding an NAD-malate dehydrogenase in the marine red alga Pyropia haitanensis. The nucleotide sequence of PhMDH was 1521 bp, including an open reading frame (ORF) of 984 bp. The amino acid sequence showed 73% identity with other MDHs in proteobacteria. Two MDH-like domains were detected in the 5–145 and 156–320 regions. Real-time fluorescent quantitative PCR (qPCR) was used to examine mRNA expression levels during the gametophyte and sporophyte phases. The transcription of PhMDH in the gametophyte was barely detectable, whereas PhMDH in the sporophyte showed a much higher expression level. The activity of PhMDH in the filamentous sporophyte was approximately double that of the leafy gametophyte. Considering these results, we suggest that PhMDH may be localized in the cytosol and play a role in carbon fixation in the sporophyte stage.