Freshwater diatoms as source of lipids for biofuel (original) (raw)
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Because of the decreasing fossil fuel supply and increasing greenhouse gas (GHG) emissions, microalgae have been identified as a viable and sustainable feedstock for biofuel production. The major effect of the release of wastewater rich in organic compounds has led to the eutrophication of freshwater ecosystems. A combined approach of freshwater diatom cultivation with urban sewage water treatment is a promising solution for nutrient removal and biofuel production. In this study, urban wastewater from eutrophic Hussain Sagar Lake was used to cultivate a diatom algae consortium, and the effects of silica and trace metal enrichment on growth, nutrient removal, and lipid production were evaluated. The nano-silica-based micronutrient mixture Nualgi containing Si, Fe, and metal ions was used to optimize diatom growth. Respectively, N and P reductions of 95.1% and 88.9%, COD and BOD reductions of 91% and 51% with a biomass yield of 122.5 mg L À1 day À1 and lipid productivity of 37 mg L À1 day À1 were observed for cultures grown in waste water using Nualgi. Fatty acid profiles revealed 13 different fatty acids with slight differences in their percentage of dry cell weight (DCW) depending on enrichment level. These results demonstrate the potential of diatom algae grown in wastewater to produce feedstock for renewable biodiesel production. Enhanced carbon and excess nutrient utilization makes diatoms ideal candidates for co-processes such as CO 2 sequestration, biodiesel production, and wastewater phycoremediation.
EFFECT OF SILICON ON GROWTH AND BIODIESEL PRODUCTION IN FRESH WATER DIATOMS
Plant Archives, 2011
The present work describes the effect of silicon (Na2SiO3.6H2O) on biodiesel production and growth of freshwater diatoms. The results revealed that the growth of diatoms in terms of number of cells was better at lower concentrations of silicon. Maximum growth (1x104 cells/ml) could be recorded at 0.05 mg/l which was maintained upto 1.0 mg/l of silicon concentration. However, the growth of diatoms decreased considerably with the increasing concentration of silicon beyond 1.0 mg/l. When the silicon concentration was increased to 5.0 mg/l, the growth of diatoms was reduced drastically (4x103 cells/ml). The minimum growth (2 x 102) of diatoms in terms of number of cells was recorded in presence of 50 mg/l of silicon. The addition of silicon as a supplement was responsible for more chitin production which produced more biodiesel. It was also observed that the rate of biodiesel production was maximum at 900C.
Potential of lipid metabolism in marine diatoms for biofuel production
Biotechnology for Biofuels, 2015
Background: Diatoms are an ecologically relevant group of microalgae that are not commonly considered for bio-oil production even if they are responsible for massive blooms at sea. Seventeen diatom species were screened for their capacity to produce biomass and lipids, in relation to their growth rate. Triglyceride levels were also assessed as a preferential source of biofuels. Results: Using statistical analysis, two centric diatoms, Thalassiosira weissflogii and Cyclotella cryptica, were selected as good candidates for oil production. Lipid levels significantly increased when the two diatoms were cultivated in a two-stage process under nitrogen limitation. The effect was less pronounced in cultures where silicon was reduced to 20% of the standard supply. Nitrogen limitation did not affect growth rates but led to lipid remodeling and de novo synthesis of triacylglycerols. Conclusions: Triacylglycerols in T. weissflogii and C. cryptica can account for up to 82% and 88% of total glycerolipids, thereby suggesting that the two species are promising candidates for large-scale experimentation for biofuel production.
The Place of Diatoms in the Biofuel Industry
In spite of attractive attributes, diatoms are underrepresented in research and literature related to the development of microalgal biofuels. Diatoms are highly diverse and have substantial evolutionarily-based differences in cellular organization and metabolic processes relative to chlorophytes. Diatoms have tremendous ecological success, with typically higher productivity than other algal classes, which may relate to cellular factors discussed in this review. Diatoms can accumulate lipid equivalently or to a greater extent than other algal classes, and can rapidly induce triacylglycerol under Si limitation, avoiding the detrimental effects on photosynthesis, gene expression and protein content associated with N limitation. Diatoms have been grown on production scales for aquaculture for decades, produce value-added products and are amenable to omic and genetic manipulation approaches. In this article, we highlight beneficial attributes and address potential concerns of diatoms as biofuels research and production organisms, and encourage a greater emphasis on their development in the biofuels arena.
The place of diatoms in the biofuels industry
In spite of attractive attributes, diatoms are underrepresented in research and literature related to the development of microalgal biofuels. Diatoms are highly diverse and have substantial evolutionarily-based differences in cellular organization and metabolic processes relative to chlorophytes. Diatoms have tremendous ecological success, with typically higher productivity than other algal classes, which may relate to cellular factors discussed in this review. Diatoms can accumulate lipid equivalently or to a greater extent than other algal classes, and can rapidly induce triacylglycerol under Si limitation, avoiding the detrimental effects on photosynthesis, gene expression and protein content associated with N limitation. Diatoms have been grown on production scales for aquaculture for decades, produce value-added products and are amenable to omic and genetic manipulation approaches. In this article, we highlight beneficial attributes and address potential concerns of diatoms as biofuels research and production organisms, and encourage a greater emphasis on their development in the biofuels arena.
Advantageous characteristics of the diatom Chaetoceros gracilis as a sustainable biofuel producer
Biotechnology for Biofuels, 2016
Background: Diatoms have attracted interest as biofuel producers. Here, the contents of lipids and photosynthetic pigments were analyzed in a marine centric diatom, Chaetoceros gracilis. This diatom can be genetically engineered using our previously reported transformation technique and has a potential to produce valuable materials photosynthetically. Sustainable culture conditions for cost-effective production of biological materials under autotrophic conditions with atmospheric carbon dioxide were investigated in the laboratory. A large-scale, open-air culture was also performed. Results: Cell population doubling time was ~10 h under continuous illumination without CO 2 enrichment, and large amounts of triacylglycerols (TAG) and fucoxanthin accumulated under a wide range of salinity and nutrient conditions, reaching ~200 and 18.5 mg/L, respectively. It was also shown that C. gracilis produced high amounts of TAG without the need for nitrogen or silica deprivation, which is frequently imposed to induce lipid production in many other microalgae. Furthermore, C. gracilis was confirmed to be highly tolerant to changes in environmental conditions, such as salinity. The diatom grew well and produced abundant lipids when using sewage water or liquid fertilizer derived from cattle feces without augmented carbon dioxide. High growth rates (doubling time <20 h) were obtained in a large-scale, open-air culture, in which light irradiance and temperature fluctuated and were largely different from laboratory conditions. Conclusions: The ability of this microalga to accumulate TAG without nutrient deprivation, which incurs added labor, high costs, and complicates scalability, is important for low-cost industrial applications. Furthermore, its high tolerance to changes in environmental conditions and high growth rates observed in large-scale, open-air culture implied scalability of this diatom for industrial applications. Therefore, C. gracilis would have great potential as a biofactory.
Sustainable Biofuel Production from Estuarine Diatoms
Green Chemistry & Technology Letters, 2020
Purpose of the study: Microalgae with better carbon sequestration potential, higher biomass, and lipid productivity in comparison to terrestrial counterparts is emerging as a viable sustainable alternative to fossil fuels. Diatoms, a subgroup of a broader category of microalgae are well-known for their role as a bio-indicator in palaeo-climatological studies across historical timelines. Understanding ecology, community structure, and habitat preference of diatoms are prerequisites for prioritizing diatom strains towards sustainable biofuel production along with value-added product extraction. Method: Selection of appropriate strains, economically viable harvesting and environmentally sound transesterification are the challenges faced in microalgal industry. The present study focusses on understanding the variability in benthic diatom community assemblages across seasons and its affinity to different substrata at fixed sampling locations in an estuarine eco-system through field sampl...
Optimization of growth conditions and fatty acid analysis for three freshwater diatom isolates
Diatoms are a group of highly abundant and diverse aquatic algae species. They contain high lipid content along with many bioactive compounds that can be exploited for biotechnological applications. Despite these attractive attributes, diatoms are underrepresented in production projects due to difficulties in their cultivation. To optimize the growth of three freshwater diatom isolates, Cyclotella sp., Synedra sp. and Navicula sp., an orthogonal assay on N, P, Si and Fe, as well as temperature and pH, was designed using traditional single-factor tests. We also studied the effect of using nanosilica as an alternate Si source on growth and found that the diatom isolates studied achieved their highest growth rates under different combinations of nutrient and environmental conditions. Silica had the greatest influence on growth, followed by phosphate and iron. The optimized growth conditions for Synedra sp. were N: 30 mg L −1 , P: 3 mg L −1 , Si: 14.8 mg L −1 , Fe: 0.448 mg L −1 , temperature 25 C and pH 8. For Navicula sp.: N: 20 mg L −1 , P: 2.5 mg L −1 , Si: 19.7 mg L −1 , Fe: 0.112 mg L −1 , temperature 30 C and pH 7.5-8. For Cyclotella sp.: N: 20 mg L −1 , P: 2.5 mg L −1 , Si: 19.7 mg L −1 , Fe: 0.448 mg L −1 , temperature 30 C and pH 7.5-8. Nano silica negatively affected growth in Navicula sp. and Cyclotella sp., but no such effect was observed in Synedra sp. Fatty acid profiling showed C16:0, C16:1(n − 7), C18:0 and C20:5(n − 3) as major fatty acids, with no significant differences in fatty acid methyl ester profiles between traditional and modified media. This work gives us a new insight into the growth requirements of freshwater diatom species, which are less studied than marine species.
The feasibility of biodiesel production by microalgae using industrial wastewater
Bioresource Technology, 2012
This study investigated nitrogen and phosphorus assimilation and lipid production of microalgae in industrial wastewater. Two native strains of freshwater microalgae were evaluated their biomass growth and lipid production in modified BBM medium. Chlamydomonas sp. TAI-2 had better biomass growth and higher lipid production than Desmodesmus sp.TAI-1. The optimal growth and lipid accumulation of Chlamydomonas sp. TAI-2 were tested under different nitrogen sources, nitrogen and CO 2 concentrations and illumination period in modified BBM medium. The optimal CO 2 aeration was 5% for Chlamydomonas sp. TAI-2 to achieve maximal lipid accumulation under continuous illumination. Using industrial wastewater as the medium, Chlamydomonas sp. TAI-2 could remove 100% NH 4 + -N (38.4 mg/L) and NO 3 À -N (3.1 mg/L) and 33% PO 4 3À -P (44.7 mg/L) and accumulate the lipid up to 18.4%. Over 90% of total fatty acids were 14:0, 16:0, 16:1, 18:1, and 18:3 fatty acids, which could be utilized for biodiesel production.
Natural Science, 2014
The effects of nitrogen, phosphorus and vitamin on growth and lipid content of a freshwater microalgae Scenedesmus sp. were investigated under indoor conditions. Nitrogen, phosphorus and vitamin presented significant statistical effect on lipid content, and a maximum lipid content of 29.3% was obtained, corresponded to increases of 90% when compared to those obtained with the original nutrients medium. On the other hand, only nitrogen and phosphorus presented significant statistical effect on cell growth, achieving ash free dry biomass, algal density, and specific growth rate of 1.3 g•L −1 , 1.5E+07 cells mL −1 , and 0.62 d −1 , respectively. By the use of the desirability function, it was possible to maximize the cell growth and lipid content simultaneously. The fatty acid composition of the microalgal lipid comprises over 80% of saturated and monounsaturated fatty acids. Thus, Scenedesmus sp. biomass could be used as suitable feedstock for biodiesel production.