Climate change, energy use and food security are the main challenges that our society is facing nowadays. Biofuels and feedstock from microalgae can be part of the solution if high and continuous production is to be ensured. This could be attained in year-round, low cost, outdoor cultivation systems using strains that are not only champion producers of desired compounds but also have robust growth in a dynamic climate. Using microalgae strains adapted to the local conditions may be advantageous particularly in Nordic countries. Here, we review the current status of laboratory and outdoor-scale cultivation in Nordic conditions of local strains for biofuel, high-value compounds and water remediation. Strains suitable for biotechnological purposes were identified from the large and diverse pool represented by saline (NE Atlantic Ocean), brackish (Baltic Sea) and fresh water (lakes and rivers) sources. Energy-efficient annual rotation for cultivation of strains well adapted to Nordic climate has the potential to provide high biomass yields for biotechnological purposes
At Nordic latitudes, year-round outdoor cultivation of microalgae is debatable due to seasonal variations in productivity. Shall the same species/strains be used throughout the year, or shall seasonal-adapted ones be used? To elucidate this, a laboratory study was performed where two out of 167 marine microalgal strains were selected for intended cultivation at the west coast of Sweden. The two local strains belong to Nannochloropsis granulata (Ng) and Skeletonema marinoi (Sm142). They were cultivated in photobioreactors and compared in conditions simulating variations in light and temperature of a year divided into three growth seasons (spring, summer and winter). The strains grew similarly well in summer (and also in spring), but Ng produced more biomass (0.225 vs. 0.066 g DW L−1 day−1) which was more energy rich (25.0 vs. 16.6 MJ kg−1 DW). In winter, Sm142 grew faster and produced more biomass (0.017 vs. 0.007 g DW L−1 day−1), having similar energy to the other seasons. The higher energy of the Ng biomass is attributed to a higher lipid content (40 vs. 16% in summer). The biomass of both strains was richest in proteins (65%) in spring. In all seasons, Sm142 was more effective in removing phosphorus from the cultivation medium (6.58 vs. 4.14 mg L−1 day−1 in summer), whereas Ng was more effective in removing nitrogen only in summer (55.0 vs. 30.8 mg L−1 day−1). Our results suggest that, depending on the purpose, either the same or different local species can be cultivated, and are relevant when designing outdoor studies. © 2021 The Authors.
There is an increasing interest in algae-based biomass produced outdoors in natural and industrial settings for biotechnological applications. To predict the yield and biochemical composition of the biomass, it is important to understand how the transcriptome of species and strains of interest is affected by seasonal changes. Here we studied the effects of Nordic winter and summer on the transcriptome of two phytoplankton species, namely the diatom Skeletonema marinoi (Sm) and the eustigmatophyte Nannochloropsis granulata (Ng), recently identified as potentially important for biomass production on the west coast of Sweden. Cultures were grown in photobioreactors in simulated Nordic summer and winter, and the gene expression in two phases was quantified by Illumina RNA-sequencing. Five paired comparisons were made among the four conditions. Sm was overall more responsive to seasons since 70 % of the total transcriptome (14,783 genes) showed differential expression in at least one comparison as compared to 1.6 % (1403 genes) for Ng. For both species, we observed larger differences between the seasons than between the phases of the same season. In summer phase 1, Sm cells focused on photosynthesis and polysaccharide biosynthesis. Nitrate assimilation and recycling of intracellular nitrogen for protein biosynthesis were more active in summer phase 2 and throughout winter. Lipid catabolism was upregulated in winter relative to summer to supply carbon for respiration. Ng favored lipid accumulation in summer, while in winter activated different lipid remodeling pathways as compared to Sm. To cope with winter, Ng upregulated breakdown and transport of carbohydrates for energy production. Taken together, our transcriptome data reveal insights into adaptive seasonal responses of Sm and Ng important for biotechnological applications on the west coast of Sweden, but more work is required to decipher the molecular mechanisms behind these responses.
Energy efficient cultivation is the major bottleneck for microalgal biomass production on a large scale and considered very difficult to attain at northern latitudes. In this study an unconventional method for industrial microalgae cultivation for bio-oil production using pulp and paper mill waste resources while harvesting only once a year was performed, mainly in order to investigate the energy efficiency of the process. Algae were cultivated for three months in 2014 in covered pond systems with access to flue gas and waste heat from the industry, and the biomass was recovered as thick sediment sludge after dewatering. The cultivation systems, designed to manage the waste resources, reached a promising photosynthetic efficiency of at most 1.1%, a net energy ratio (NER) of 0.25, and a projected year-round energy biomass yield per area 5.2 times higher than corresponding rapeseed production at the location. Thus, microalgae cultivation was, for the first time, proven energy efficient in a cold continental climate. Energy-rich indigenous communities quickly out-competed the oleaginous monocultures used for inoculation. The recovered biomass had higher heating values of 20–23 MJ kg− 1 and contained 14–19% oil dominated by C16 followed by C18 fatty acids. The cultivation season at 59°15′N, 14°18′E was projected to be efficient for 10 months and waste heat drying of the biomass is suggested for two winter months. The technique is proposed for carbon sequestering and energy storage in the form of microalgal sludge or dry matter for later conversion into biochemicals.
The hue parameter of HSV colour-space for digital imaging is shown to be accessible for convenient quantitative fluorescence imaging. A commercially available pH probe was utilized in solution and incorporated into optical μ-sensors for microscopy applications.
Drinking water contamination of lead from various environmental sources, leaching consumer products, and intrinsic water-pipe infrastructure is still today a matter of great concern. Therefore, new highly sensitive and convenient Pb2+ measurement schemes are necessary, especially for in-situ measurements at a low cost. Within this work dye/ionophore/Pb2+ co-extraction and effective water phase de-colorization was utilized for highly sensitive lead measurements and sub-ppb naked-eye detection. A low-cost ionophore Benzo-18-Crown-6-ether was used, and a simple test-tube mix and separate procedure was developed. Instrumental detection limits were in the low ppt region (LOD = 3, LOQ = 10), and naked-eye detection was 500 ppt. Note, however, that this sensing scheme still has improvement potential as concentrations of fluorophore and ionophore were not optimized. Artificial tap-water samples, leached by a standardized method, demonstrated drinking water application. Implications for this method are convenient in-situ lead ion measurements.
Background and aims: Wound healing requires appropriate oxygen and pH levels.Oxygen therapy and pH‐modulating treatments have shown positive effects onwound healing. Thus, a dressing, which combines high levels of dissolved oxygen(DO) with the pH of intact skin, may improve wound healing. Our aims were to (1) formulatean in situ gelling dressing with high levels of DO and with the pH level of intactskin, (2) evaluate physical and chemical properties of the dressing, and (3) elucidatebasic effects of elevated levels of DO on human skin cells in vitro.Methods: A dressing was formulated with 15 to 16 wt% poloxamer 407, acetatebuffer, and oxygenated water. Stability of pH and DO, rheology, and shelf life wereanalysed. Furthermore, in vitro studies of the effect of increased levels of DO wereperformed.Results: An in situ gelling wound dressing, with a DO concentration rangingbetween 25 and 35 mg/L and a pH of 5.5, was formulated. The DO concentrationwas stable above 22 mg/L for at least 30 hours when applied on a surface at 35°Cand covered for directed diffusion into the intended wound area. At storage, thedressing had stable pH for 3 months and stable DO concentration over 30 mg/L for7 weeks. Increasing DO significantly enhanced intracellular ATP in human skin cells,without changing reactive oxygen species production, proliferation rate, or viability.Conclusion: The developed dressing may facilitate wound healing by deliveringcontrolled and stable oxygen levels, providing adjustable pH for optimized healing,and increasing intracellular ATP availability.
In this study we reintroduce phase separation efficiency as an important characteristic for biodiesel quality and blending. The ability of the fuel to emulsify water is possibly one of the most important features behind biological and chemical fuel degradation but yet, no methods that directly measure this property are included in the standard biodiesel regulation EN14214. The proposed simple technique for fuel quality testing is based on the time it takes for ultra-purified water to become transparent after complete mixing with an equal volume of fuel, measured by kinetic absorbance spectrophotometry. In this study we screen the phase separation efficiency (measured as separation time) of purified, un-aged and aged Fatty Acid Methyl Esters (FAME/B100) and its blends with EN590 with 7% FAME without detergents (B7 reference fuel Euro VI Part no 546061-35 and B100) as well as for FAME blends with a commercial EN590. The B7 fuel was used as reference in all measurements. Aged biodiesel (FAME/B100) almost doubled (1.8 times) its separation time compared to the un-aged FAME/B100 sample and had almost three times (2.9) longer phase separationtime relative the reference B7 fuel. Also fuel blends showed long separation times. A fuel blend based on aged FAME/B100 blended with B7 to a corresponding B30 (30% FAME) gave after three consecutive 10 s mixings stable emulsions (>30 min) in two out of three replicates. All fuels blended with commercial EN590 showed excellent phase separation efficiencies with significantly shorter separation times than FAME/B100. We also show that the phase separation efficiency of the B30 blend could be improved after the rape seed ester was vacuum distilled before blending with B7 petrodiesel. The results indicate that likely emulsion problems associated with the B30 blends can be circumvented with proper selection of compatible petroleum components as well as FAME purifications.
The overall objective of this study was to firmly investigate if the refueling frequency influences the degradation rate of biodiesel and find out if primary and secondary oxidation products can act as initiators for biodiesel degradation in absence of metals. Duplicate samples of B7 Reference fuel Euro VI and B100 methyl rape seed ester were studied during accelerated aging in an open to dry atmosphere system at an elevated temperature (80 °C) during 14 days. Determinations of water, short chain fatty acids as well as structural changes using infrared spectroscopy were used as degradation measures during aging and complemented with total acid number and hydroperoxide concentration at the end of the experiment. The study clearly shows that there are no autocatalytic effects from left over fuel after refueling and thus, the primary and secondary products do not directly influence the degradation rate of the fuel and that the fuel quality are in fact improved after refueling as the remaining degradation products are diluted.