Insights into cell wall disintegration of Chlorella vulgaris

With their ability of CO2 fixation using sunlight as an energy source, algae and especially microalgae are moving into the focus for the production of proteins and other valuable compounds. However, the valorization of algal biomass depends on the effective disruption of the recalcitrant microalgal cell wall. Especially cell walls of Chlorella species proved to be very robust. The wall structures that are responsible for this robustness have been studied less so far. Here, we evaluate different common methods to break up the algal cell wall effectively and measure the success by protein and carbohydrate release. Subsequently, we investigate algal cell wall features playing a role in the wall’s recalcitrance towards disruption. Using different mechanical and chemical technologies, alkali catalyzed hydrolysis of the Chlorella vulgaris cells proved to be especially effective in solubilizing up to 56 wt% protein and 14 wt% carbohydrates of the total biomass. The stepwise degradation of C. vulgaris cell walls using a series of chemicals with increasingly strong conditions revealed that each fraction released different ratios of proteins and carbohydrates. A detailed analysis of the monosaccharide composition of the cell wall extracted in each step identified possible factors for the robustness of the cell wall. In particular, the presence of chitin or chitin-like polymers was indicated by glucosamine found in strong alkali extracts. The presence of highly ordered starch or cellulose was indicated by glucose detected in strong acidic extracts. Our results might help to tailor more specific efforts to disrupt Chlorella cell walls and help to valorize microalgae biomass.

Continuous Rotation of Three Large Biomass Crops With High Bioconcentration Factor of Cadmium Can Effectively Repair Contaminated Farmlands

Traditional phytoremediation is one means for remediation of heavy metal pollution. For developing countries, the key factor in promoting the practical application of phytoremediation in polluted soils is selecting suitable plants tolerant to heavy metals and using these to produce products with economic value. A chicory-tobacco-peanut, three-season, rotation field experiment was carried on the utilization and remediation of cadmium (Cd) in contaminated farmlands. The results showed that all three crops had a strong capacity to accumulate Cd, with bioconcentration factors of chicory, tobacco, and peanut 6.61 to 11.97, 3.85 to 21.61, and 1.36 to 7, respectively. The yield of total dry biomass and phytoextraction efficiency for Cd reached 32.4 t ha-1 and 10.3% per year, respectively. The aboveground tissues of the three crops accounted for 83.9–91.2% of the total biomass in this rotation experiment. The content of peanut grain and oil met the National Food Safety Standard of China (0.5 mg kg-1, GB 2762-2017) and the Food Contaminant Limit of the European Union (0.1 mg kg-1, 18812006). Therefore, in addition to being used for phytoremediation in contaminated soils, this crop rotation system can also lead to economic benefits for local farmers.

Trait differences between and within ranges of an invasive legume species

Novel ecological interactions can drive natural selection in non-native species and trait evolution may increase the likelihood of invasion. We can gain insight into the potential role of evolution in invasion success by comparing traits of successful individuals in the invasive range with the traits of individuals from the native range in order to determine which traits are most likely to allow species to overcome barriers to invasion. Here we used Medicago polymorpha , a non-native legume species from the Mediterranean that has invaded six continents around the world, to quantify differences in life history traits among genotypes collected from the native and invasive range and grown in a common greenhouse environment. We found significant differences in fruit and seed production and biomass allocation between invasive and native range genotypes. Invasive genotypes had greater fecundity, but invested more energy into belowground growth relative to native genotypes. Beyond the variation between ranges, we found additional variation among genotypes within each range in flowering phenology, total biomass, biomass allocation, and fecundity. We found non-linear relationships between some traits and fitness that were much stronger for plants from the invasive range. These trait differences between ranges suggest that stabilizing selection on biomass, resource allocation, and flowering phenology imposed during or after introduction of this species may increase invasion success.

Macrozoobentos on the shelf of the Kronotsky Gulf

Data about the taxonomic composition and spatial distribution of bottom invertebrates of Kronotsky Gulf were obtained on results of bottom grab survey carried in September 2002. Analysis of the samples revealed 72 species of Polychaeta, 21 species of molluscs (Bivalvia), 17 species of crustaceans (mostly Amphipoda), 2 species of echinodermata (Echinoidea and Ophiuroidea). The average biomass in the depth range 25–200 m was 242±116 g/m2 where average density was 306±51 organisms/m2. The most high values of biomass were observed in the outlet parts of the rivers Zhupanova, Semyachik, Kronotskaya, where contribution of sea dollar Echinarachnius parma communities was principal. Despite fluctuations of the biomass of particular taxons during 50 years, the total biomass keeps stable (206–242 g/m2). Like in 1949 E. parma plays the main role in most bottom communities.

Camelina sativa (L. Crantz) Fresh Forage Productive Performance and Quality at Different Vegetative Stages: Effects of Dietary Supplementation in Ionica Goats on Milk Quality

The research meant to study the productive performances of Camelina sativa and the effects of feeding Camelina fresh forage harvested during five phenological stages (I: main stem elongation; II: maximum stem elongation: III: inflorescence appearance; IV: flowering; V: fruit set visible) on the yield, chemical composition and fatty acid profile of milk from autochthonous Ionica goats. Goats were randomly assigned to two groups (n = 15) that received a traditional forage mixture (Control) or Camelina forage harvested at different stages (CAM). The field experiment was conducted in two years; no significant differences between years were recorded for any of the Camelina production traits. The total biomass increased (p < 0.05) from phase I (1.4 t/ha) to phase V (5.2 t/ha). The distribution of stem, leaves and pod also changed during growth, showing a significant increase of stem from 40.8 to 45.6% and of pod from 0 to 19.4%, whereas leaves decreased from 59.2 to 35.1%. The milk yield and chemical composition were unaffected by the diet, while supplementation with Camelina forage increased milk CLA content (on average 1.14 vs. 0.78%). A markedly higher concentration of PUFAs was found in milk from goats fed Camelina harvested during the last three phenological stages. The index of thrombogenicity of milk from the CAM fed goats was significantly lower compared to the control group. In conclusion, Camelina sativa is a multi-purpose crop that may be successfully cultivated in Southern Italy regions and used as fresh forage for goat feeding. Milk obtained from Camelina fed goats showed satisfactory chemical and fatty acid composition, with potential benefits for human health.

Planned Application of Sewage Sludge Recirculates Nutrients to Agricultural Soil and Improves Growth of Okra (Abelmoschus esculentus (L.) Moench) Plants

The aim of this study was to investigate the feasibility of using sewage sludge (SS) biosolids as a low-cost soil fertilizer to improve soil characteristics and crop yields. Okra (Abelmoschus esculentus (L.) Moench) plants were grown in soil supplemented with different concentrations of SS (0, 10, 20, 30, 40, and 50 g/kg). The results showed that SS soil application led to improved soil quality with a 93% increase of organic matter (at SS dose of 10 g/kg), decreased pH (a reduction from 8.38 to 7.34), and enhanced macro- and micro- nutrient contents. The levels of all the investigated heavy metals (HMs; Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in the postharvest SS-amended soil were within the prescribed safe limits. The application of SS to soil considerably enhanced the growth parameters of okra plants. Total biomass increased 13-fold and absolute growth rate increased 10-fold compared to plants grown in nonamended (control) soils. Among the applied SS doses, the 10 g/kg SS dose led to the highest values of the measured growth parameters, compared to those of plants grown in control soils. The induced growth at 10 g/kg SS was accompanied by a substantial increase in metal content in roots, stems, leaves, and fruits; however, all levels remained within safe limits. Consequently, the data presented in this study suggest that SS could be used as a sustainable organic fertilizer, also serving as an ecofriendly method of SS recycling.

RADIATION SAFETY ASSESSMENT OF CARROT AND BEET PRODUCTS CULTIVATED IN THE BLACK EARTH ZONE OF RUSSIA IN THE OREOL OF THE EASTERN CHERNOBYL TRACE

On the territory of the Plavsky radioactive hotspot of the Tula region of Russia, formed as a result of the accident at the Chernobyl nuclear power plant in 1986, an assessment of the radiation safety of growing carrots and beets was carried out in 2019. It has been established that at present the content of 137Cs in arable leached chernozems of the surveyed lands is 90–170 kBq/m2 , which is 2.5–4.5 times higher than the permissible level of density of surface radioactive contamination of soils. However, the specific activity of the radionuclide in carrot and beetroot crops does not exceed 5 Bq/kg, which is significantly less than the maximum permissible level of 137Cs accumulation in vegetables (600 Bq/kg for absolutely dry weight). The accumulation coefficients of 137Cs in the total biomass of carrots and beets are 2.0·10−2 and 7.5·10−2, and in eaten root crops – 1.1·10−2 and 2.0·10−2, respectively, which is in good agreement with the IAEA estimate for the intensity of the transition 137Cs in the production of vegetable roots from loamy and clayey soils.

Effects of Different Soils on the Biomass and Photosynthesis of Rumex nepalensis in Subalpine Region of Southwestern China

The performance of Rumex nepalensis, an important medicinal herb, varies significantly among subalpine grasslands, shrublands and forest ecosystems in southwestern China. Plant–soil feedback is receiving increasing interest as an important driver influencing plant growth and population dynamics. However, the feedback effects of soils from different ecosystems on R. nepalensis remain poorly understood. A greenhouse experiment was carried out to identify the effects of different soil sources on the photosynthesis and biomass of R. nepalensis. R. nepalensis was grown in soils collected from the rooting zones of R. nepalensis (a grassland soil, RS treatment), Hippophae rhamnoides (a shrub soil, HS treatment), and Picea asperata (a forest soil, PS treatment). The chlorophyll contents, net photosynthetic rates, and biomasses of R. nepalensis differed significantly among the three soils and followed the order of RS > HS > PS. After soil sterilization, these plant parameters followed the order of RS > PS > HS. The total biomass was 16.5 times higher in sterilized PS than in unsterilized PS, indicating that the existence of soil microbes in P. asperata forest ecosystems could strongly inhibit R. nepalensis growth. The root to shoot biomass ratio of R. nepalensis was the highest in the sterilized PS but the lowest in the unsterilized PS, which showed that soil microbes in PS could change the biomass allocation. Constrained redundancy analysis and path analysis suggested that soil microbes could impact the growth of R. nepalensis via the activities of soil extracellular enzymes (e.g., β-1,4-N-acetylglucosaminidase (NAG)) in live soils. The soil total soluble nitrogen concentration might be the main soil factor regulating R. nepalensis performance in sterilized soils. Our findings underline the importance of the soil microbes and nitrogen to R. nepalensis performance in natural ecosystems and will help to better predict plant population dynamics.

Aquatic Vegetation Loss and Its Implication on Climate Regulation in a Protected Freshwater Wetland of Po River Delta Park (Italy)

Aquatic vegetation loss caused substantial decrease of ecosystem processes and services during the last decades, particularly for the capacity of these ecosystems to sequester and store carbon from the atmosphere. This study investigated the extent of aquatic emergent vegetation loss for the period 1985–2018 and the consequent effects on carbon sequestration and storage capacity of Valle Santa wetland, a protected freshwater wetland dominated by Phragmites australis located in the Po river delta Park (Northern Italy), as a function of primary productivity and biomass decomposition, assessed by means of satellite images and experimental measures. The results showed an extended loss of aquatic vegetated habitats during the considered period, with 1989 being the year with higher productivity. The mean breakdown rates of P. australis were 0.00532 d−1 and 0.00228 d−1 for leaf and stem carbon content, respectively, leading to a predicted annual decomposition of 64.6% of the total biomass carbon. For 2018 the carbon sequestration capacity was estimated equal to 0.249 kg C m−2 yr−1, while the carbon storage of the whole wetland was 1.75 × 103 t C (0.70 kg C m−2). Nonetheless, despite the protection efforts over time, the vegetation loss occurred during the last decades significantly decreased carbon sequestration and storage by 51.6%, when comparing 2018 and 1989. No statistically significant effects were found for water descriptors. This study demonstrated that P. australis-dominated wetlands support important ecosystem processes and should be regarded as an important carbon sink under an ecosystem services perspective, with the aim to maximize their capacity to mitigate climate change.

Effects of nitrogen and phosphorus availability on the early growth of two congeneric pairs of savanna and forest species

In the tropical region, savannas and seasonal forests, both highly diverse biomes, occur side by side, under the same climate. If so, that mosaic cannot be explained solely by climatic variables, but also by fire, water availability and soil status. Nutrient availability in the soil, especially nitrogen and phosphorus, has been postulated to explain the abrupt transitions between savannas and seasonal forests in tropical regions. Plants from these two biomes may present different nutritional strategies to cope with nitrogen and phosphorus limitation. We used two congeneric pairs of trees — each pair with a species from the savanna and another from the neighboring seasonal forest — to test whether savanna and forest species presented different nutritional strategies during their early development. We cultivated 56 individuals from each of these species in a hydroponics system with four treatments: (1) complete Hoagland solution, (2) Hoagland solution without nitrogen, (3) Hoagland solution without phosphorus, and (4) Hoagland solution without nitrogen and phosphorus. After 45 days, we harvested the plants and measured total biomass, root to shoot ratio, height, leaf area, and specific leaf area. Overall, savanna species were lighter, shorter, with smaller leaves, higher specific leaf areas, and higher root to shoot ratios when compared to the forest species. Nitrogen increased the performance of species from both biomes. Phosphorus improved the performance of the forest species and caused toxicity symptoms in the savanna species. Hence, savanna and forest species presented different demands and were partially distinct already as seedlings concerning their nutritional strategies.