Microalgae cultivation for lipids and carbohydrates production

Microalgae are photoautotrophic microorganisms that can produce energy both by using sunlight, water and CO2 (phototrophic metabolism) and by using organic sources such as glucose (heterotrophic metabolism). Heterotrophic growth is a key factor in microalgae research, due to its increased productivity and the lower capital and operative costs compared to photoautotrophic growth in photobioreactors. Carbohydrate production from microalgae is usually investigated for the production of biofuels (e.g. bioethanol) by successive fermentation, but also other applications can be envisaged in biopolymers. In this work an increment in carbohydrate purity after lipid extraction was found. Protein hydrolysis for different microalgae strains (Scenedesmus sp. and Chlorella sp.) was investigated. Microalgae were cultivated under photoautotrophic or heterotrophic conditions, collecting biomass at the end of the growth. Biomass samples were dried or freeze dried and used for carbohydrate and lipid extraction tests. Lipid extraction was achieved using different organic solvents (methanol-chloroform and hexane-2propanol). Basic protein hydrolysis has been carried out testing different temperatures and NaOH concentrations values. Lipids were spectrophotometrically quantified, while residual biomass was saccharificated and the total amount of sugars was measured. Significant differences about the purity of extracted carbohydrates were found comparing dried with freeze dried biomass. However, not a very promising purification of carbohydrates was achieved after protein hydrolysis, asking for further analysis. © Copyright 2017, AIDIC Servizi S.r.l

The effects of minimal tillage, contour cultivation and in-field vegetative barriers on soil erosion and phosphorus loss.

Runoff, sediment, total phosphorus and total dissolved phosphorus losses in overland flow were measured for two years on unbounded plots cropped with wheat and oats. Half of the field was cultivated with minimum tillage (shallow tillage with a tine cultivator) and half was conventionally ploughed. Within each cultivation treatment there were different treatment areas (TA). In the first year of the experiment, one TA was cultivated up and down the slope, one TA was cultivated on the contour, with a beetle bank acting as a vegetative barrier partway up the slope, and one had a mixed direction cultivation treatment, with cultivation and drilling conducted up and down the slope and all subsequent operations conducted on the contour. In the second year, this mixed treatment was replaced with contour cultivation. Results showed no significant reduction in runoff, sediment losses or total phosphorus losses from minimum tillage when compared to the conventional plough treatment, but there were increased losses of total dissolved phosphorus with minimum tillage. The mixed direction cultivation treatment increased surface runoff and losses of sediment and phosphorus. Increasing surface roughness with contour cultivation reduced surface runoff compared to up and down slope cultivation in both the plough and minimum tillage treatment areas, but this trend was not significant. Sediment and phosphorus losses in the contour cultivation treatment followed a very similar pattern to runoff. Combining contour cultivation with a vegetative barrier in the form of a beetle bank to reduce slope length resulted in a non-significant reduction in surface runoff, sediment and total phosphorus when compared to up and down-slope cultivation, but there was a clear trend towards reduced losses. However, the addition of a beetle bank did not provide a significant reduction in runoff, sediment losses or total phosphorus losses when compared to contour cultivation, suggesting only a marginal additional benefit. The economic implications for farmers of the different treatment options are investigated in order to assess their suitability for implementation at a field scale

Nannochloropsis oceanica cultivation in pilot-scale raceway ponds—from design to cultivation

Raceways ponds are the microalgal production systems most commonly used at industrial scale. In this work, two di erent raceway configurations were tested under the same processing conditions to compare their performance on the production of Nannochloropsis oceanica. Biomass productivity, biochemical composition of the produced biomass, and power requirements to operate those reactors were evaluated. Water depths of 0.20 and 0.13 m, and culture circulation velocities of 0.30 and 0.15 m s1 were tested. A standard configuration, which had a full channel width paddlewheel, proved to be the most energy e cient, consuming less than half of the energy required by a modified configuration (had a half channel width paddlewheel). The later showed to have slightly higher productivity, not enough to o set the large di erence in energetic consumption. Higher flow velocity (0.30 m s1) led to a 1.7 g m2 d1 improvement of biomass productivity of the system, but it increased the energy consumption twice as compared to the 0.15 m s1 flow velocity. The latter velocity showed to be the most productive in lipids. A water depth of 0.20 m was the most suitable option tested to cultivate microalgae, since it allowed a 54% energy saving. Therefore, a standard raceway pond using a flow velocity of 0.3 m s1 with a 0.20 m water depth was the most e cient system for microalgal cultivation. Conversely, a flow velocity of 0.15 m s1 was the most suitable to produce lipids.Portugal 2020 Program (POCI-01-0247-FEDER-035234; LISBOA-01-0247-FEDER-035234; ALG-01-0247-FEDER-035234)info:eu-repo/semantics/publishedVersio

Bacterial diversity assessment in Antarctic terrestrial and aquatic microbial mats : a comparison between bidirectional pyrosequencing and cultivation

The application of high-throughput sequencing of the 16S rRNA gene has increased the size of microbial diversity datasets by several orders of magnitude, providing improved access to the rare biosphere compared with cultivation-based approaches and more established cultivation-independent techniques. By contrast, cultivation-based approaches allow the retrieval of both common and uncommon bacteria that can grow in the conditions used and provide access to strains for biotechnological applications. We performed bidirectional pyrosequencing of the bacterial 16S rRNA gene diversity in two terrestrial and seven aquatic Antarctic microbial mat samples previously studied by heterotrophic cultivation. While, not unexpectedly, 77.5% of genera recovered by pyrosequencing were not among the isolates, 25.6% of the genera picked up by cultivation were not detected by pyrosequencing. To allow comparison between both techniques, we focused on the five phyla (Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Deinococcus-Thermus) recovered by heterotrophic cultivation. Four of these phyla were among the most abundantly recovered by pyrosequencing. Strikingly, there was relatively little overlap between cultivation and the forward and reverse pyrosequencing-based datasets at the genus (17.1–22.2%) and OTU (3.5–3.6%) level (defined on a 97% similarity cut-off level). Comparison of the V1–V2 and V3–V2 datasets of the 16S rRNA gene revealed remarkable differences in number of OTUs and genera recovered. The forward dataset missed 33% of the genera from the reverse dataset despite comprising 50% more OTUs, while the reverse dataset did not contain 40% of the genera of the forward dataset. Similar observations were evident when comparing the forward and reverse cultivation datasets. Our results indicate that the region under consideration can have a large impact on perceived diversity, and should be considered when comparing different datasets. Finally, a high number of OTUs could not be classified using the RDP reference database, suggesting the presence of a large amount of novel diversity

Dry matter and fibre yields, and the fibre characteristics of five nettle clones (Urtica dioica L.) organically grown in Austria for potential textile use

The aim of the field trial was to quantifiy yield, fibre content and fibre quality of 5 fibre nettle clones cultivated according to the principles of organic farming. The field trial started in 1997 and was organized in a randomised block design with 4 replications per clone. The field trial was situated in Neulengbach, Lower Austria. Since fibre nettle does not provide sufficient yields in the first cultivation year, the harvest of the second and third cultivation year (1998 respectively 1999) was used for calculation of yield per hectar and for the analysis of fibre content and quality. The dry matter yield (stalks) of the 5 nettle clones in the second cultivation year (1998) lies between 2,3 – 4,7 t/ha. Clone 1 and Clone 7 achieve the highest yields. This result was statistically significant. The dry matter yields of that year correspond with the dry matter yield achieved under extensive cultivation conditions (without nitrogen fertilizer) as described by SCHMIDKE ET AL. (1998). The dry matter yields of the third cultivation year (5,6 – 9,7 t/ha), however, are more than twice as high as those of the second cultivation year. They are also higher than the yields from the nitrogen intensive cultivation system described by VETTER ET AL. (1996) with 200 kg N/ha + 100 kg N/ha after the first cutting (per year; the fertilizer used was calcium ammonium nitrate). This large increase in yield in the third cultivation year is caused by an increase in the height (20 – 40 cm higher) and by the production of runners: the number of stalks per plot more than doubled in the third cultivation year. Additionally the undersowing of clover (Trifolium repens) seems to have had a positive effect on the growing of fibre nettle. The fibre yields lie between 335 – 411 kg/ha in the second cultivation year and between 743 – 1.016 kg/ha in the third cultivation year. Clones with a high dry matter yield have a low fibre content and vice versa. Therefore the differences between the clones in dry matter yield/ha and fibre content are balanced and there is no more difference between the fibre yield/ha of the clones. The fibre content after chemical processing lies in both the second and the third cultivation year between 8 – 16 % drymatter (stalks). This result confirms the maximum fibre contents reported in recent literature (DREYER ET AL. 1996, DREYER & DREYLING 1997, SCHMIDTKE ET AL. 1998, KÖHLER ET AL. 1999, FRANCKEN-WELZ ET AL. 1999). Clone 8 and Clone 9 have the highest fibre content in 1998 (16,0 respectively 14,5 %), and Clone 8 (15,7 %) in 1999. There is no significant difference between the fibre quality (fibre strength, elongation, fibre fineness, lenght of fibre) of the five nettle clones. In general the fibre material is very inhomogeneous, which is caused by the differing consistence of the upper and the lower part of the stalk and by fibre processing methods. In principle, nettle fibres are suitable for textile use, however, the further developement of an economic and functional method for processing along with high yields is essential. The results show that higher yields and fibre contents were achieved in the third cultivation year under the described cultivation conditions of organic farming than other authors (BREDEMANN 1959, VETTER ET AL. 1996, DREYER ET AL. 1996, SCHMIDTKE ET AL 1998, FRANCKEN-WELZ ET AL. 1999). The yields of the third cultivation year are higher than the minimum for economic cultivation as defined by DREYER & DREYLING (1997). The cultivation of fibre nettle under the conditions of organic farming in Austria is therefore possible, as long as fibre processing plants and consumer demand exists. There is a need for further research in optimizing cultivation methods in organic farming (undersowing of leguminosae, manuring with slurry, row width, crop rotation) as well as in optimizing fibre processing methods for the quality of raw materials available and taking into account further processing into textiles (e.g. production of a pure yarn or a mixed yarn with cotton). There is also a need for research into possibilities to use fibres from different parts of the nettle plant for different purposes (e.g. textile and industrial uses)

A global view of shifting cultivation: Recent, current, and future extent

Mosaic landscapes under shifting cultivation, with their dynamic mix of managed and natural land covers, often fall through the cracks in remote sensing–based land cover and land use classifications, as these are unable to adequately capture such landscapes’ dynamic nature and complex spectral and spatial signatures. But information about such landscapes is urgently needed to improve the outcomes of global earth system modelling and large-scale carbon and greenhouse gas accounting. This study combines existing global Landsat-based deforestation data covering the years 2000 to 2014 with very high-resolution satellite imagery to visually detect the specific spatio-temporal pattern of shifting cultivation at a one-degree cell resolution worldwide. The accuracy levels of our classification were high with an overall accuracy above 87%. We estimate the current global extent of shifting cultivation and compare it to other current global mapping endeavors as well as results of literature searches. Based on an expert survey, we make a first attempt at estimating past trends as well as possible future trends in the global distribution of shifting cultivation until the end of the 21st century. With 62% of the investigated one-degree cells in the humid and sub-humid tropics currently showing signs of shifting cultivation—the majority in the Americas (41%) and Africa (37%)—this form of cultivation remains widespread, and it would be wrong to speak of its general global demise in the last decades. We estimate that shifting cultivation landscapes currently cover roughly 280 million hectares worldwide, including both cultivated fields and fallows. While only an approximation, this estimate is clearly smaller than the areas mentioned in the literature which range up to 1,000 million hectares. Based on our expert survey and historical trends we estimate a possible strong decrease in shifting cultivation over the next decades, raising issues of livelihood security and resilience among people currently depending on shifting cultivation

Effects of culivation conditions for apples on growth rates of fruit fly larvae and contents of phenolics

The different cultivation treatments significantly and systematically affected both rate of development of fruit fly larvae and contents of phenolic compounds, but not the total number of flies produced. This is in accordance with the hypothesis that cultivation methods can give large enough changes in composition of plant foods to affect physiological aspects important for health of consumers. It indicates that further stusies should be made of the links between plant cultivation, plant composition and health, for example regarding the question of the nutritional value of organic versus conventional food

The impact of shifting cultivation in the forestry ecosystems of timor-leste

Every year thousands of hectares of forest are destructed as a result of the practice of swidden agriculture, shifting cultivation or "slush and burn" causing changes in forest ecosystems. In Timor- Leste shifting cultivation is still practiced nowadays as a form of subsistence agriculture. Swidden agriculture is characterized by slash and burn clearing, by a rotation of fields rather than of crops, and by short periods of cropping (1-3 years) alternating with long fallow periods. Based on the characterization of shifting cultivation in two Sucos of Bobonaro district, a reflection is made on the impact of this practice in the sustainable development of forest ecosystems of Timor- Leste. Primary data collection was performed using a questionnaire survey of farmers practicing shifting cultivation. The questionnaire characterized shifting cultivation, and asked farmers’ opinion on slash and burning of forest areas and on the importance of forests. According to the results obtained, in most situations the existing vegetation before the slash was composed of dense forest, the slash is made by the family group, the majority of farmers have been doing the “slush and burn” for more than ten years and the size of the plots where slash is made is less than 2 hectares. The materials resulting from the slash are used for firewood, building materials and fencing. The burning of vegetable residues is done before planting and soil preparation and sowing is done with a lever. Land and forest, despite having an individual use, have a tenure regime of ownership and access in which its nature of common pool good prevails. Every year thousands of hectares of forest are destructed as a result of the practice of swidden agriculture, shifting cultivation or "slush and burn" causing changes in forest ecosystems. In Timor-Leste shifting cultivation is still practiced nowadays as a form of subsistence agriculture

The problem of causality in cultivation research

This paper offers an up-to-date review of problems in determining causal relationships in cultivation research, and considers the research rationales of various approaches with special reference to causal interpretation. It describes in turn a number of methodologies for addressing the problem and resolving it as far as this is possible. The issue of causal inference arises not only in cultivation research, however, but is basic to all media effects theories and approaches primarily at the macro-level whose main methodology rests on correlational studies (agenda-setting, spiral of silence, knowledge gap hypothesis, etc.). We therefore first discuss problems of causal interpretation in connection with the cultivation hypothesis, and then sketch in summary how these problems arise with other media effects theories. We first set out the basic features of the cultivation approach, then consider the difficulties with correlational studies and discuss alternative research designs - designs which are not original to us, but have been adapted for cultivation research. These comprise laboratory experiments, sequential studies, social studies and time-series procedures. Finally, we argue for multiple approaches that complement one another's advantages and balance out their disadvantages