Enhancement of C-phycocyanin productivity by Arthrospira platensis when growing on palm oil mill effluent in a two-stage semi-continuous cultivation mode

Palm oil mill effluent (POME) is well known as agricultural wastewater that has a high potential as a medium for microalgal growth due to its high macro- and micronutrient content. The cyanobacterium Arthrospira platensis is considered as a species with a high C-phycocyanin (C-PC) content which is important for fine chemical and pharmaceutical applications. However, cultivation of A. platensis on POME to produce economically feasible amounts of C-PC has not been well explored. For this, environmental, nutritional, and cultivation modes (batch, semi-continuous) were varied to optimize C-PC productivity when cultivated at various POME concentrations. Arthrospira platensis was found to grow well on POME. Highest biomass and C-PC concentrations were found on 30–100% POME. Central composite rotatable design (CCRD) response surface methodology demonstrated that C-PC productivity was influenced by urea addition at the optimum salinity. The highest C-PC productivity was found on 100% POME during semi-continuous cultivation, while the addition of phosphorus and urea did not significantly improve C-PC productivity. By applying semi-continuous cultivation with 50% POME at the first stage and 100% POME at the second stage, a similarly high C-PC productivity (4.08 ± 1.3 mg L−1 day−1) was achieved as compared with (artificial) Zarrouk medium during batch cultivation. We conclude that, when using a two-stage semi-continuous cultivation process, A. platensis can produce economically feasible amounts of C-PC when cultivated on 100% POME

Structural Elucidation of Agrochemical Metabolic Transformation Products Based on Infrared Ion Spectroscopy to Improve In Silico Toxicity Assessment

Toxicological assessments of newly developed agrochemical agents consider chemical modifications and their metabolic and biotransformation products. To carry out an in silico hazard assessment, understanding the type of chemical modification and its location on the original compound can greatly enhance the reliability of the evaluation. Here, we present and apply a method based on liquid chromatography-mass spectrometry (LC-MS) enhanced with infrared ion spectroscopy (IRIS) to better delineate the molecular structures of transformation products before in silico toxicology evaluation. IRIS facilitates the recording of IR spectra directly in the mass spectrometer for features selected by retention time and mass-to-charge ratio. By utilizing quantum-chemically predicted IR spectra for candidate molecular structures, one can either derive the actual structure or significantly reduce the number of (isomeric) candidate structures. This approach can assist in making informed decisions. We apply this method to a plant growth stimulant, digeraniol sinapoyl malate (DGSM), that is currently under development. Incubation of the compound in Caco-2 and HepaRG cell lines in multiwell plates and analysis by LC-MS reveals oxidation, glucuronidation, and sulfonation metabolic products, whose structures were elucidated by IRIS and used as input for an in silico toxicology assessment. The toxicity of isomeric metabolites predicted by in silico tools was also assessed, which revealed that assigning the right metabolite structure is an important step in the overall toxicity assessment of the agrochemical. We believe this identification approach can be advantageous when specific isomers are significantly more hazardous than others and can help better understand metabolic pathways

Variability of protistan and bacterial communities in two Arctic fjords (Spitsbergen)

Krossfjorden and Kongsfjorden are Arctic fjords on the western side of Spitsbergen. These fjords share a common mouth to the open sea, and both are influenced by the input of sediment-rich glacial meltwater leading to decreased surface salinity, increased turbidity and decreased light penetration during summer. Earlier classical taxonomic studies had described the pelagic protistan composition of the Kongsfjorden during summer, revealing the dominance of flagellates of often unresolved taxonomic origin. Only little information existed on microbial eukaryote composition of the Krossfjorden as well as the bacterial composition of both fjords. The aim of the present study was to analyze and compare surface summertime protistan and bacterial communities in both fjords, using molecular approaches (16S and 18S rRNA DGGE, sequencing). Samples were collected three times a week from the central Kongsfjorden over a 1-month period. Additionally, 10 marine and 2 freshwater sites were sampled within a 1-week period in both Kongsfjorden and Krossfjorden. The central Kongsfjorden revealed a relatively stable protistan community over time with dinoflagellates, chlorophytes and small heterotrophs dominating. In contrast, the bacterial community varied over time and appeared to be correlated with the inflow of glacial meltwater. The Kongsfjorden and Krossfjorden were found to harbor distinctive bacterial and eukaryotic communities. We speculate that differences in glacial meltwater composition and fjord bathymetry affect the surface water properties and therefore the observed spatial variability in the community fingerprints.</p

Environmental and nutrient conditions influence fucoxanthin productivity of the marine diatom Phaeodactylum tricornutum grown on palm oil mill effluent

Palm oil mill effluent (POME) is a type of wastewater posing large problems when discharged in the environment. Yet, due to its high nutrient content, POME may offer opportunities for algal growth and subsequent harvesting of high-value products. The marine diatom Phaeodactylum tricornutum is a potential feedstock diatom for bioactive compounds such as the carotenoid fucoxanthin, which has been shown to have pharmaceutical applications. The aim of this paper was to evaluate the growth and fucoxanthin productivity of P. tricornutum grown on POME, as a function of light intensity, temperature, salinity, and nutrient enrichment. High-saturating irradiance (300molphotonsm(-2)s(-1)) levels at 25 degrees C showed highest growth rates but decreased the fucoxanthin productivity of P. tricornutum. Box-Behnken response surface methodology revealed that the optimum fucoxanthin productivity was influenced by temperature, salinity, and the addition of urea. Nutrient enrichment by phosphorus did not enhance cell density and fucoxanthin productivity, while urea addition was found to stimulate both. We conclude that POME wastewater, supplemented with urea, can be considered as the potential medium for P. tricornutum to replace commercial nutrients while producing high amounts of fucoxanthin.</p

Solar radiation, and solar radiation driven cycles in warming and fresh water discharge control seasonal and inter-annual phytoplankton chlorophyll a and taxonomic composition in a high Arctic fjord (Kongsfjorden, Spitsbergen)

Fjords on the west coast of Spitsbergen experience variable Arctic and Atlantic climate signals that drive seasonal and inter-annual variability of phytoplankton productivity and composition, by mechanisms that are not fully resolved. To this end, a time series (2013–2018) of Kongsfjorden (N 78�54.2, E 11�54.0) phytoplankton pigments, ocean physics, nutrient concentrations, and microbial abundances was investigated. Kongsfjorden phy- toplankton dynamics were predominantly governed by solar radiation and cycles of warming and freshwater dis- charge that caused pronounced changes in light and nutrient availability. Phytoplankton growth after the polar night commenced in March in a mixed, nutrient loaded water column, and accelerated in April after weak ther- mal stratification. Spring (weeks 10–22) showed high diatom relative abundance that ceased when silicic acid and nitrate reached limiting concentrations. Summer (weeks 23–35) was characterized by sixfold stronger stratification due to increased freshwater discharge and continued ocean heating. This caused a warm, low salinity surface layer with low nutrient concentrations. Small and diverse flagellates, together with high bacterial and viral abundances, thrived in this regenerative, N or P-limited system. Elevated late summer chlorophyll a (Chl a), and ammonium suggested increased regeneration and nutrient pulses by glacial upwelling. Fall (weeks 36–48) caused rapidly declining Chl a and increasing diatom relative abundance, which persisted throughout the polar night, causing high diatom relative abundance during spring. Despite inter-annual variability in ocean temperature and salinity we observed relatively stable seasonal phytoplankton taxonomic composition and Chl a

Novel nano-composite multi-layered biomaterial for the treatment of multifocal degenerative cartilage lesions

We report on a 46-year-old athletic patient, previously treated with anterior cruciate ligament reconstruction, with large degenerative chondral lesions of the medial femoral condyle, trochlea and patella, which was successfully treated with a closing-wedge high tibial osteotomy and the implant of a newly developed biomimetic nanostructured osteochondral bioactive scaffold. After 1 year of follow-up the patient was pain-free, had full knee range of motion, and had returned to his pre-operation level of athletic activity. MRI evaluation at 6 months showed that the implant gave a hyaline-like signal as well as a good restoration of the articular surface, with minimal subchondral bone oedema. Subchondral oedema was almost non-visible at 12 months

Interannual variability in phytoplankton biomass and species composition in northern Marguerite Bay (West Antarctic Peninsula) is governed by both winter sea ice cover and summer stratification

The rapid warming of the West Antarctic Peninsula region has led to reduced sea ice cover and enhanced glacial melt water input. This has potential implications for marine ecosystems, notably phytoplankton growth, biomass, and composition. Fifteen years (1997–2012) of year-round size fractionated chlorophyll a (Chl a), phytoplankton pigment fingerprinting and environmental data were analyzed to identify the relationship between sea ice cover, water column stability and phytoplankton dynamics in northern Marguerite Bay, Antarctica. Over the investigated period, both summer (December–February) and winter biomass declined significantly, 38.5% and 33.3% respectively. Winter phytoplankton biomass was low ( 20 μm) fraction was strongly decreased in the low biomass years, from 92% to 39%, coinciding with a smaller diatom fraction in favor of nanophytoplankton ( 95%) during summers with average-to-high biomass. We advance a conceptual model whereby low winter sea ice cover leads to low phytoplankton biomass and enhanced proportions of nanophytoplankton, when this coincides with reduced stratification during summer. These changes are likely to have a strong effect on the entire Antarctic marine food web, including krill biomass, and distribution