Journal of Applied Phycology最新文献

Red microalgae from the Cyanidiophyceae, particularly Galdieria sulphuraria and Cyanidioschyzon merolae, are primitive photosynthetic thermoacidophiles that thrive in acidic hot springs and geysers. Unlike most Cyanidiophyceae, Galdieria strains are metabolically flexible as they can switch from photoautotrophic growth in the light to heterotrophic growth in complete darkness. Galdieria sulphuraria is especially noteworthy for its accumulation of various commercially valuable, functional compounds such as glycogen and phycocyanin. Glycogen, a branched fractal-like polysaccharide composed of several thousands of anhydroglucopyranose units, can be added to cosmetic products and sports drinks as a moisturizer or slow-digestible carbohydrate. While the production and structural characteristics of the glycogen of G. sulphuraria 108.79, isolated from Yellowstone National Park, have been previously described, our investigation aimed to explore glycogen production and properties across various Galdieria strains from different locations. Our findings reveal that all examined strains produce substantial amounts of highly branched glycogen when grown heterotrophically on glycerol in the dark. Notably, the structural characteristics of Galdieria glycogen distinguish it from both eukaryotic and prokaryotic glycogen, exhibiting a significantly higher degree of branching, substantially shorter side chains, and a considerable extent of indigestibility. These findings support the hypothesis that this highly branched, small glycogen is a long-term energy store, enabling survival during extended periods of complete darkness.

Cyanobacteria, a group of prokaryotic photoautotrophs, are accredited for trace metal sequestration due to their ability to produce various siderophores and are widely utilised for bioremediation. In this context, we investigated the ability of cyanobacterium Anabaena oryzae for removal of cadmium. Cadmium toxicity disrupts crucial physiological processes in photosynthetic organisms, inhibits growth, reduces photosynthetic efficiency, etc. thereby, truncating nutrient cycling. Structural elucidation of siderophore produced by A. oryzae through FTIR, mass spectrometry, 1D and 2D NMR (COSY, HSQC and NOESY) depicted tetradentate denticity and conspicuous presence of dihydroxamate along with unique spatial arrangement of atoms, conferring novel structure. Furthermore, the physiological and biochemical studies by administering iron and cadmium, individually as well as in combinations, exhibited cadmium-mediated toxicity in the cyanobacterium, ultimately reducing physiological capacity, whereas iron possessed ameliorating effect. Nevertheless, the possibility of Cd-induced siderophore production was shown by higher production of siderophore in presence of cadmium. Proteome profiling further displayed regulation of siderophore synthesis through cadmium supplementation. Moreover, negative binding energies of transporter proteins like OmpA, Pbp, ABC type-transporter and TonB with siderophore-Cd complex, shown by in silico docking studies, suggested uptake and thereby removal of cadmium by A. oryzae. This study addresses the problem of cadmium toxicity in cyanobacteria and explores the potential of A. oryzae to mitigate this toxicity through siderophore production and metal removal. It also contributes to the understanding of siderophore-mediated metal sequestration and introduces a novel siderophore candidate with promising prospects for cadmium remediation.

The application of macroalgae for food and feed has been increasing continuously due to their nutritional and health-promoting properties. Efficient post-harvest drying is needed to remove moisture content from macroalgal biomass without negatively affecting its nutritional value. We hypothesized that low-temperature oven drying would preserve most of the nutrients and polyphenols in macroalgae. The polyphenol-rich brown macroalga, Fucus vesiculosus, was exposed to one of the following treatments: freeze-drying (FD; for 72 h), oven drying at 40 ℃ (OD40; for 24 h), and oven drying at 80 ℃ (OD80; for 24 h). The concentration of total fatty acids and the sum of saturated, mono-, and polyunsaturated fatty acids exhibited a decreasing trend with higher drying temperatures (FD > OD40 > OD80), indicating the sensitivity of fatty acids to a high drying temperature. However, the sum of total or essential amino acids was significantly higher (p < 0.05) in OD80 compared to OD40 and FD biomass. In this study, the average N-protein-conversion factor for dried F. vesiculosus remained relatively stable (~ 4.64) across drying treatments. The total polyphenol content remained unaffected by the drying treatment, although it tended to decrease with increasing drying temperature. Targeted metabolomics revealed three classes of phenolic compounds: phenylpropanoids, flavones, and flavonols. A low-temperature oven drying appears to be a suitable method to preserve nutrients and polyphenols in brown macroalgae. Future studies are needed to evaluate the impact of drying methods on other bioactive compounds and to understand the economic sustainability of oven drying.

This experiment was carried out to evaluate the effect of dietary supplementation of three different tropical seaweed species on rumen fermentation, methane emission, antioxidant status, immunity and milk production in lactating Murrah buffaloes. Twenty-four lactating Murrah buffaloes were divided into four groups of six each in an experiment based on randomized block design (RBD) and were fed to meet their nutrient requirements (ICAR 2013). Animals in control (CON) group were fed basal diet without any supplemental seaweed, however, Kappaphycus alvarezii (KA), Gracilaria salicornia (GS) and Turbinaria conoides (TC) were supplemented at 1% of the dietary dry matter in KA, GS and TC groups, respectively. Intake and apparent digestibility of nutrients, plasma concentrations of selected blood metabolites, and thyroid hormones were similar among the groups. Supplementation of KA and GS, but not TC increased (P < 0.001) the proportion of propionate in rumen fluid with a concurrent decrease (P < 0.001) in acetate: propionate. The enteric methane emission was lower (P < 0.05) in KA, GS groups and the maximum values were observed in groups CON and TC. Total antioxidant capacity (TAC) and immune response (cell-mediated and humoral) were higher (P < 0.001), and MDA was lower (P < 0.001) in seaweed-fed groups as compared to CON; the higher response was observed in group KA, followed by TC and GS. Plasma concentration of cortisol was lower (P < 0.001) in group KA as compared to other groups. Milk yield and the 6% fat-corrected milk (FCM) yield (kg day⁻¹) were higher (P = 0.009) in KA, followed GS, corresponding values in group TC were not significantly different than those of group CON. Thus, supplementation of the tropical red seaweed improved antioxidant status, cellular and humoral immunity, and milk yield; the greater response was obtained when KA was used as feed supplement. It is concluded that supplementation of K. alvarezii at 1% of dietary DM of lactating Murrah buffaloes would improve antioxidant status, immunity and milk yield with reduction in enteric methane emission.

In the field of industrial microalgae production, the introduction of parasitic contaminants is an often-neglected topic, but one that represents a major risk with potentially significant financial implications. So far, no successful strategy exists to maintain a long-term stable cultivation environment in industrial photobioreactors. To create a strategy for preventing and controlling parasitic contamination, methods from synthetic ecology were used, replacing monocultures with mixed-biocoenoses. The goals were the identification of microbiotic ecosystems of potentially symbiotic bacteria and the utilization of synergistic effects between bacteria and algae to stabilize cultures. The final aim was to combine the findings with abiotic factors influencing the infections. As model organisms, the microalga Coelastrella vacuolata (formerly Scenedesmus vacuolatus) and the parasitic contaminant Amoeboaphelidium protococcarum were chosen. For this case, a correlation between infection rate and the chlorophyll a fluorescence in the culture was found. Algal co-cultures with specific bacteria were tested using the protecting effects of antiphytopathogenic, extracellular substances. This led to the bacterium Pseudomonas protegens and the naturally antipathogenic phenol 2,4-diacetylphloroglucinol (DAPG). Co-cultures with DAPG-producing P. protegens effectively inhibited the infection even though no quantifiable amounts of DAPG were found in the culture. Furthermore, abiotic influences on the infection process were identified, resulting in the implementation of a light–dark-cycle with induced anaerobic conditions in the dark phase. With these findings, conditions that inhibit the growth of parasitic contaminants could now be introduced preventively within standard cultivation procedures.

Fulvic acid (FA) is an active humic substance and is found to improve the antioxidant defence system under unfavourable conditions. Dunaliella salina is a unicellular microalga and is a rich source of β-carotene. In this study the impact of fulvic acid (FA) was investigated on some physiological parameters, H₂O₂ production, antioxidant metabolites, and enzymatic responses related to the ascorbate (ASA)-glutathione (GSH) pathway in D. salina. Results showed that 100 mg FA L⁻¹ maintained the D. salina cell growth compared to control, and exhibited as a suitable treatment to induce carotenoids compared to 50 FA mg L⁻¹. However, 200 FA mg L⁻¹ significantly decreased the cell biomass. FA (100 mg L⁻¹) enhanced the total carotenoids (3.92 pg cell⁻¹), β-carotene (2.46 pg cell⁻¹), and lutein (0.81 pg cell⁻¹) after 7 days, which was accompanied by a reduction in the chlorophyll a and b. Cell number did not change significantly under FA and cells trended to be round in shape after 7 days. Protein content showed an insignificant change, while H₂O₂ level was promoted by FA treatment, which was related to the regulation of the ASA-GSH pathway. The activity of ascorbate peroxidase, superoxide dismutase, and dehydroascorbate reductase was more promoted in the FA-treated cells, while glutathione reductase activity and glutathione content were just induced under Sevier oxidative conditions. The findings of this research suggest new insights into the inducing impact of FA on the ASA-GSH pathway and carotenoid biosynthesis to regulate the ROS level in D. salina.

Gelidium elegans is a marine red alga widely distributed in the northwestern Pacific Ocean. In Taiwan, wild populations of G. elegans have been gradually declining over the past decade due to global warming and overharvesting. Two types of cultivation experiments with G. elegans were conducted: spore germination experiments under four different temperature conditions and a growth experiment to test the growth condition and longevity of G. elegans in a controlled environment. The sporeling temperatures were set to simulate seawater temperatures between 18 °C and 25 °C, corresponding to seawater temperatures from March to May in Northern Taiwan. This period aligns with the peak growth season for G. elegans. The purpose of this setup was to provide optimal conditions for the germination and growth of seedlings of G. elegans for indoor cultivation. Most of the tetraspores germinated into seedlings under the four temperature conditions (18 °C, 20 °C, 22 °C, 25 °C). However, the seedlings grown between 22 °C and 25 °C stopped growing and turned white after 30–50 days of cultivation. On the other hand, the juveniles cultivated at 18 °C reached adult size (more than 10 cm in length) after more than a year of cultivation in the laboratory. In comparison, the juveniles at 20 °C grew slower than those at 18 °C. In the longevity experiment, the subculture thalli thrived well after three years of cultivation in a controlled environment. Next, outdoor culture experiments will be conducted under natural conditions with different nutrient and irradiance regimes to test the sensitivity of juveniles to water temperature.

Seaweed aquaculture, which takes place mostly in Asia, is a lucrative industry that is valued > US $9 billion. However, technological modifications are needed to ensure economic viability and growth of the seaweed aquaculture industry throughout Europe. While current research is investigating the use of certain mechanised processes in seaweed aquaculture, the impact of pressurised spraying of macroalgal cultures on subsequent growth remains unknown. Here, we aimed to determine the efficacy of a future mechanised seeding procedure by investigating how differing pressure treatments impact upon the growth and percentage cover of zoospores seeded onto twine in the hatchery, using the kelp Saccharina latissima as a model species. Zoospore solutions were subjected to pressures of 1, 2, 3, 4, and 5 bar, before being seeded on hatchery twine and left to grow for 7 weeks. We demonstrate that both percentage cover and sporophyte lengths for S. latissima are significantly reduced by ~ 22% and ~ 61%, respectively, when juvenile zoospores are subjected to increasing pressure from 1 to 5 bar. This indicates that minimal pressure in the use of mechanised hatchery techniques is optimal for growth of seaweed.

The growth of microalgae under different trophic modes is widely considered in the literature. However, the cultivation of some microalgal strains under heterotrophic conditions requires further investigation. Thus, the present study investigated the growth potential of a Brazilian strain of Tetradesmus obliquus (Chlorophyceae, Scenedesmaceae) in terms of heterotrophic metabolism. For this purpose, cultures were generated using different concentrations of glucose (26, 13, and 6.5 g L^–1) and sodium nitrate (0.6 g, 0.3, and 0.15 g L^–1) in culture media. The growth parameters analysed were the maximum biomass achieved and volumetric productivity. The combination of 26 g L^–1 glucose with 0.6 g L^–1 sodium nitrate resulted in the greatest increase in dry weight (9.63 ± 0.15 g L^–1). Then, T. obliquus cultures under heterotrophic conditions were compared with those under photoautotrophic and mixotrophic conditions. The maximum production in heterotrophic cultivation was similar to what had been obtained, while mixotrophic cultivation presented the best result, 14.77 ± 0.06 g L^–1, and photoautotrophic cultivation obtained a maximum biomass of 7.90 ± 0.17 g L^–1. The productivity values achieved were 0.52 ± 0.04 g L^–1 day^–1, 0.98 ± 0.07 g L^–1 day^–1, and 1.24 ± 0.07 g L^–1 day^–1 for photoautotrophic, heterotrophic and mixotrophic cultures, respectively. The results indicated that the Brazilian microalga T. obliquus has the potential to be successfully cultivated heterotrophically.

Graphical Abstract

Microalgae are gaining considerable attention in the field of cosmeceuticals due to their unique profile. In particular, the diverse range of valuable bioactive compounds isolated from microalgae are known to exhibit multiple properties, including anti-aging, antioxidant, whitening, moisturising, and photoprotection, which have contributed to their distinctive profile. In recent years, there has been an increasing effort around exploration of novel natural biologically active substances from microalgae. This trend is in part driven by the global progression towards a ‘greener’ lifestyle. Since compounds derived from microalgae can offer skin benefits without inducing any adverse effects on human health, they are recognised as promising ingredients for innovative cosmetics and cosmeceutical applications. This review paper provides an overview of the changing balance of reliance on traditional topical agents and the prominent role of microalgae as an alternative source for whitening, photo-protection and anti-aging cosmetic applications.

Graphical abstract