1,720,994 research outputs found
Bacterial Populations in Freshwater Aquaculture Ponds
No full textIn an aquatic pond ecosystem different microbial communities are involved in the recycling of organic materials. The bacterial communities involved in the organic decomposition and nutrient cycling in ponds with manure applications of: (i) cow manure at 10 t/ ha/ yr; urea at 100 kg N/ha/yr and single super phosphate at 50 kg P/ ha / yr ; (ii) biogas slurry at 30 t /ha/yr with supplementary feed were assessed over a period of 15 months .
Populations of selected bacterial communities were assessed in the fish Pond ecosystems to assess the levels of substrate utilization
Biotic Communities in Fish Pond Ecosystems
No full textBiotic communities in fish ponds in Odisha, India under four treatments
comprising : (i) cow manure at 1Ot/ha/yr, urea at 100 kg N/ha/yr, and single super phosphate at 50 kg P/ha/yr; (ii) biogas slurry at 15 t/ha/yr and inorganic fertilizers as in the previous treatment; (iii) biogas slurry at 30 t/ha/yr ; and (iv) and biogas slurry at 30 t/ha/yr with supplementary
feed were studied for a period of fifteen months
Integrated Farming System Approach A Global Overview
No full textThe global demand for food production will increase becau se of rapid
population growth and increased competition for land and water. The
ever increasing demand for water in agriculture is one of the key limiting
factors for food production. Thus, producing more food for each drop of
water is vital for addressing water scarcity a n d food insecurity. This chapter
provides an overview of integrated aquaculture-agriculture (IAA) that has
great potential to increase food productivity and reduce risks associated
with water scarcity. IAA also provides a wide range of social, economic
and environmental benefits. It is therefore, recognised that IAA produces
'more cropper drop'
Recirculatory Aquaculture Systems An Environmentally Safe and Sustainable Method of Fish Production
No full textProducing more food from the same area of land while reducing the environmental impacts requires what has been called sustainable
intensification wrote Godfray et al.(2010) in a recent review about the
challenge of feeding 9 billion people. Todate, most land - based production
of species of major commercial importance , like : catfish, hybrid striped bass, trout, tilapia, etc., has b een in ponds, raceways, or estuarine
impoundments. Traditional production practices of these and other species
require large amounts of good quality water, a limited resource in many
areas. In our modern world the condition of many water sources in some areas no longer favors these production practices
Application of lipid extracted algae in feed and energy production
No full textSubmitted in fulfillment of the requirements for the Doctor of Philosophy: Biotechnology, Durban University of Technology, Durban, South Africa, 2019.Microalgae are well considered to be promising feedstocks for biodiesel production. Microalgae can be grown under different types of cultivation conditions and their biomass has tremendous potential to be used as biofuel feedstock and for other applications such as feed, food, cosmetics, pharmaceutical etc. Despite the many benefits and the significant development in the field of microalgal biodiesel production, there are several challenges including high cultivation cost and developing efficient downstream processing methods. The biomass production cost is high, which significantly hinders the use of microalgae as a feedstock. Most of the available literature is focused on upstream, single strain and single product strategy, where mainly algal lipids are used for biofuel production. Hence, for improving the sustainability of the algal biofuel production processes and related process economics, a multiple applications approach using integrated biorefinery and exploiting microalgae for environmental benefits is required.
To explore the microalgal biorefinery concept it is vital to understand the various cultivation conditions and applications of biomass in different sectors. There are various strategies, which have potential to make algal biofuel technologies more economically feasible and environmentally sustainable. Use of alternative culture media, improving the biomass production and the efficiency of downstream processing (drying, cell disruption, lipid extraction etc.) algal biofuel technology economical. Utilizing lipid-extracted algae (LEA) for energy and aqua feed application will maximize overall economic return and will leave minimal residues as by-product.
The major focus of this thesis was to utilize LEA as substrate for biomethane production and protein source in aquaculture feed. However, effect of preceding steps such as microalgae cultivation, biomass drying and cell disruption on major metabolites extraction was also studied. Microalgae were cultivated in different medium (domestic wastewater and BG11) and their
biomass yields and biochemical composition (lipid, protein and carbohydrate) were compared. Different drying and cell disruption techniques were employed for lipid extraction and their effect on lipid, protein and carbohydrate yields were evaluated. The yield of major metabolites on whole cell and LEA were also compared. Suitable solvent systems were selected for optimum lipid extraction from wet and dry biomass with minimal toxic effect on LEA metabolites so that LEA can be further used for biomethane and aquaculture feed production.
The choice of microalgae at large scale depends upon the number of factors such as their adaptability to large-scale cultivation, biomass production, major metabolites content, robustness towards the open system cultivation and contamination. In this study, S. obliquus and C. sorokiniana were cultivated in wastewater and BG11 medium at laboratory scale. Both strains are indigenous to KwaZulu-Natal. C. sorokiniana showed lower biomass and major metabolites (lipid, protein and carbohydrate) production at large scale compared to S. obliquus. Considering better adaptability to open cultivation, high biomass and metabolites yields, S. obliquus strain was selected for the LEA application study.
Microalgae species, C. sorokiniana and S. obliquus were cultivated on BG11 and using different ratios of raw domestic wastewater and post-chlorinated wastewater as nutrient media. The cultivation of S. obliquus and C. sorokiniana showed biomass yield of 1.2-3.5 and 0.78-1.8 g L-1 in BG11 medium, respectively. While biomass yield observed in wastewater was 0.59-1.59 g L-1 for S. obliquus and 0.67-1.45 g L-1 for C. sorokiniana. The higher biomass yield in BG11 medium attributed to the higher nutrient contents in this medium compared to wastewater. The lipid contents for S. obliquus and C. sorokiniana were 20 and 16.5% dry cell weight (DCW), respectively when grown using BG11 medium. While increases in lipid contents of 26.25 and 29.4% DCW were found for S. obliquus and C. sorokiniana, respectively when cultivated using
wastewater. Similarly, carbohydrate contents for S. obliquus and C. sorokiniana were 18 and 17% DCW, respectively for BG11 medium. Increased in carbohydrate contents of 25% for S. obliquus, 28.4% DCW for C. sorokiniana were observed for wastewater. Microalgae tend to accumulate more lipids and/or carbohydrates under nutrient stress condition. The nitrogen and phosphorus contents in wastewater are lower than BG11 medium, which were responsible for stressed condition for microalgae. With limited nutrients in wastewater compared to BG11 medium, growth of microalgae is also lower which resulted in lower protein content. Protein content for S. obliquus and C. sorokiniana in BG11 medium were 37.83-48.8 and 25-35.3% DCW, respectively. The protein contents for S. obliquus and C. sorokiniana in wastewater medium were 16.4-27.29 and 15.8-27.3% DCW, respectively. The biochemical composition depends upon the nutrient composition of the medium and cultivation conditions.
The two selected microalgae have shown potential for nutrient removal while cultivated in wastewater. The removal efficiency by S. obliquus was found to be 76.13% for COD, 98.54% for nitrogen and 97.99% for phosphate. Microalgae C. sorokiniana cultivation in wastewater removed 69.38% COD, 86.93% nitrogen and 68.24% phosphates. Increased lipid accumulation in the cells was also recorded in stressed conditions due to low nutrient availability from wastewater.
After harvesting of microalgae from culture media, the water content in thick algal slurry (>85% DCW) lowers the products recovery. To overcome this challenge drying and cell disruption are required to enhance the efficiency of lipid extraction. Where drying and cell disruption increase the viability of biomass for lipid extraction process.
Three biomass-drying techniques viz. sun, oven and freeze-drying and four-cell disruption techniques viz. microwave, sonication, osmotic shock and autoclave disruption were studied for their effect on recovery of major metabolites from S. obliquus. Microalgae metabolites recovery
from whole cell and LEA were analysed and compared. The results showed that after lipid extraction, LEA still contained comparable protein to whole algae biomass however, the carbohydrate concentration was reduced. Oven drying exhibited the highest recovery of all the major metabolites followed by freeze-drying; sun drying however, showed lower yields. Despite lower metabolites recovery sun-drying technique is preferable at large scale due to its easy application and cost-effective nature. The main drawback of sun drying technique is weather dependence and required longer period to dry.
The microwave and autoclave microalgal cell disruption improved the lipid yield but loss of other compounds was observed. In osmotic shock treatment, due to poor cell disruption efficiency low lipid were obtained and comparably lower protein loss was noticed during lipid extraction.
Lipid extraction is crucial step for microalgae biodiesel production. Solvent-assisted lipid extraction is widely used technique for lipid recovery from dry or wet algae biomass. In a biorefinery approach, it is vital to choose appropriate solvents for the optimum lipid extraction whilst having minimal effect on the remaining metabolites (protein and carbohydrates) in LEA. LEA could be used for energy generation or aquaculture feed applications.
Six commonly used organic solvents/ solvent systems were used for lipid extraction from wet and dry biomass. The results showed that the lipid extraction efficiency depends strongly on types of biomass as well as solvent systems selected. Lipid extraction from wet algal biomass could reduce the processing steps and save energy incurred in drying. However, the water present in wet algal slurry acts as a barrier, which results in lower lipid yield compared to the dry biomass. The results revealed that among all six-selected solvents, chloroform: ethanol (1:1 v/v) was most effective if wet biomass used specifically for lipid purpose only. To explore the biorefinery concept, isopropanol/hexane composition is the most suitable solvent system because it is less toxic and
resulted in high protein (20.07% DCW) and carbohydrate (22.87%) yields in LEA. For dry algal biomass, chloroform: methanol (2:1 v/v) is an appropriate solvent system if biomass used especially for lipid (19.25%) extraction. If LEA to be used for energy and/or aquaculture feed application, DCM: methanol was found to be a suitable solvent system, which gave 32.79% protein and 26.92% carbohydrate yield. Comparatively hexane has lower lipid recovery but shown higher protein and carbohydrate yield in LEA. Due to less toxic, easy to scale up and inexpensive, hexane is preferable as a solvent for lipid extraction if LEA is to be further utilized at large scale for energy or feed application.
Anaerobic digestion (AD) of organic residues is well-researched technology for biomethane production. Whole microalgae and LEA has promising potential for biomethane production. The anaerobic sludge used as inoculum for microalgal biomass digestion. Biomethane production from whole algae and products extracted algae highly depends on sludge to algae biomass ratio for higher methane production. The extraction of metabolites also changes the biochemical composition of residual biomass, which can affect the biomethane production. It is vital to understand the effect of various product-extracted algae and as well as pre-treated algae on the biochemical methane potential.
In order to compare biomethane potential, four types of biomass were selected namely sun dried powder algae (SDPA), mild heat-treated algae (MHTA), LEA (using hexane as lipid extracting solvent) and protein-extracted algae (PEA). The average methane (CH4) production rate was ~ 2.5 times higher for protein and lipid extracted algae than for whole algae SDPA and MHTA whilst the cumulative CH4 production was higher for pre-treated algae. Highest cumulative CH4 production (318.7mL CH4 g-1 VS) was found for MHTA followed by SDPA (307.4mL CH4 g-1 VS). The CH4/CO2 ratios of 1.5 and 0.7 were observed for MHTA and LEA, respectively. Outcome
of this objective revealed that pre-treatment process disrupts the microalgae cell walls, exposing intracellular material and increasing the surface area. The product-extracted algae changes the elemental composition, which decreases the cumulative gas yield CH4/CO2 ratio. Presence of high nitrogen in the form of protein produces ammonia (NH3) which inhibits the methane production. Therefore, it is imperative to use PEA biomass to improve the methane production yield than the whole cell biomass.
Due to escalating price and unstable supply of fish meal (FM), alternative protein sources are used in aqua feed, however these sources do not meet to the requirement. The use of less expensive protein source in aquaculture feed as alternative to FM is required. Microalgae are primary producers in the food chain as well as a natural food for fish. Microalgal biomass is comprised of proteins, lipids, carbohydrates, pigments and many other bioactive compounds. The microalgal proteins have an appropriate balance of all essential amino acids, while lipids are rich in polyunsaturated fatty acids (omega-3 fatty acids, EPA, DHA). Whole algae contain all required ingredients while LEA also contain protein, carbohydrates, vitamins, bioactive compounds even though most of the lipid soluble nutrients have been removed. Thus, microalgae have promising potential to be used in aquaculture feed. Aquaculture production continues to increase globally, to meet the aquaculture feed demand algae supplemented aquaculture feed will play an important role in providing good quality fish.
In this study, approximately 200 kg of microalgal biomass was harvested for the feed application. Due to lower toxicity, ease of availability and ease of recovery from mixture, hexane was used as a lipid extracting solvent at pilot scale to generate LEA. The 44 weeks (from juvenile to finisher stage) feeding trials were conducted to evaluate the effect of whole and LEA supplementation of
S. obliquus strain on growth performance, disease tolerance, feed utilization, physiological
activity, and fillet biochemical composition of Nile tilapia (Oreochromis niloticus). In the first trial, fish were fed with an algae free diet (control) and four experimental diets (2.5, 5, 7.5 and 10 wt%) as protein source of dried S. obliquus. The study showed that microalgae could be used as a protein supplement in the Tilapia feed for enhancement of morphological characteristics and nutritional value. The 7.5% and 10% supplementation of whole algal biomass in tilapia feed showed significant improvement in weight and length of the fish compared to the control. The daily body weight gain was 0.25 g higher in experimental groups than the control. The hepatosomatic index percentage was also higher in fish feed when 7.5% whole algae was used in fish feed as a protein source. The results also showed that 7.5% and 10% have better specific growth rate (1.57 and 1.5%), daily body weight gain (1.1 and 0.86 g), overall body weight gain (427.16 and 331.48 g), protein assimilation (43.96 and 40.46%) higher than the control diet fed fish. The survival rate of fish were 100% at every inclusion level. In second trial (44 weeks), two supplementations (7.5 and 10 wt%) of LEA as protein source were used in Nile tilapia diets. Results showed 7.5% and 10% LEA supplemented feed shown better growth performance than control. The protein content were 42.2%, 41.3% and 36.1% in tilapia fed with 7.5%, 10% LEA and control feed, respectively. The body weight gain, tilapia fed with 7.5% LEA shown 357 g while 10% LEA and control have 331.78 g, and 330.08 gm, respectively. The application of whole and LEA of S. obliquus in tilapia feed, shown appropriate supplementation level for tilapia feed at demonstration scale.
This thesis presents advances in knowledge in the field of microalgae biorefinery research for pilot scale operations. This research work has covered various aspects such as effect of drying, cell disruption and lipid extraction on whole and LEA metabolites yield. The extraction of lipid from wet and dry microalgal biomass using various solvent systems provides a new insight for the
selection of appropriate solvent systems, which can be used for the large-scale lipid extraction. The study on LEA for biomethane production enhances the understanding about the effects of different pre-treatments and product extractions on biomethane production. The results revealed that the supplementation of whole cell and LEA using S. obliquus for tilapia feed is safe therefore, can be used as an alternative protein source. The findings of this study have both academic and industrial value.
Evaluation of biohydrogen production potential of sugarcane bagasse using activated sludge in a dark fermentation process
No full textSubmitted in fulfilment of the requirements Of the degree of Masters in Applied Science: Biotechnology, Durban University of Technology, Durban, South Africa, 2016.Anaerobic dark fermentation is an efficient biological process to produce hydrogen from waste material. In South Africa, this technology has not been explored adequately to extract energy from biological wastes. Within the KwaZulu Natal region of South Africa, the sugar industry is a prominent venture that produces mass quantities of sugarcane bagasse amongst other waste products. This by-product can be an ideal source of substrate for biohydrogen generation. In this study, sugarcane bagasse was used as the main substrate for biohydrogen production by anaerobic fermentation using sewage sludge as the inoculum. Different pre-treatment methods were employed to maximize the release of fermentable sugars from the lignocellulosic biomass. Among the different pre-treatment methods employed, the maximum sugar yield (294.4 mg/g) was achieved with 0.25% H2SO4 for 60 minutes at 121°C. Prior to inoculation, the sewage sludge was also subjected to thermal pre-treatment to eliminate methanogens. Thermal pre-treatment of inoculum sludge for 30 min was effective in eliminating methanogens. Fluorescence in situ hybridization was used to positively identify the hydrogen producing bacteria present before and after treatment. The pre-treated substrate and inoculum was integrated into a dark fermentation process to further optimize the effect of pH, substrate to biomass, iron and magnetite nanoparticles on hydrogen production. The maximum hydrogen production (1.2 mol/mol glucose) was achieved at a pH range of 5-6, a substrate to biomass ratio of 3.5, and iron and magnetite nanoparticle concentration of 200 mg/L. Microbial analysis using quantitative polymerase chain reaction has confirmed the dominance of Clostridium spp. in the reactor. The highest hydrogenase gene activity (number of copies of hydrogenase gene expression/ng DNA) was recorded in the reactor supplemented with magnetite nanoparticles with lowest being in the raw sludge. There was a direct positive correlation between the hydrogenase gene copy number and the hydrogen yield obtained at different reactor conditions. Scanning electron microscopy was a useful to visually analyse the interaction of microorganisms with activated sludge. This study highlights the significance of anaerobic microorganisms from waste sludge being able to utilize agricultural waste material to produce biohydrogen which could be further scaled up for continuous hydrogen production. In addition, statistical tools used to predict the possible sugar (Design of experiments) and hydrogen yields (Gompertz model) produced would be helpful in saving time during full-scale operation of biohydrogen producing reactors.
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Thermochemical conversion of biomass and upgrading of bio-products to produce fuels and chemicals
No full textThe considerable growth in energy demands and limited fossil fuel sources, together with environmental concerns, have forced the study of renewable, green and sustainable energy sources. Biomass and its residues can be transformed into valued chemicals and fuels with several thermal conversion processes, which are combustion, gasification and pyrolysis. Combustion is a chemical process that involves the rapid reaction of substances with oxygen, producing heat. Gasification produces synthesis gas at high temperatures (800–1200 °C) to generate heat and power. Pyrolysis has been applied for many years for charcoal formation, while intermediate and fast pyrolysis processes have become of significant interest in recent years. The reason for this interest is that these processes provide different bio-products (bio-oil, synthesis gas and biochar), which can be applied directly in various applications or as a sustainable energy carrier. The present chapter covers an overview of the fundamentals of slow, intermediate and fast pyrolysis, followed by the properties and applicability of the pyrolysis products. This study also identifies the features and advantages of the thermo-catalytic reforming (TCR) process in comparison with other technologies. This report presents a comprehensive literature review of bio-oil production and upgrading methods. In addition, the most common catalysts and supports for different upgrading methods are introduced. Finally, the current pathways for 2-methylfuran (2-MF) formation and the selection of xylose-rich biomass are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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