The place of diatoms in the biofuels industry (original) (raw)

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.

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.

Freshwater diatoms as source of lipids for biofuel

Until recently, biodiesel production has been derived from terrestrial plants such as soybean and canola, leading to competition between biodiesel production and agricultural production for source materials. Microalgae have the potential to synthesize 30 times more oil per hectare than terrestrial plants without competing for agricultural land. We examined four genera (Cyclotella, Aulacoseira, Fragilaria, Synedra) of common freshwater diatoms (Bacillariophyceae) for growth and lipid content in deWned medium (sD11) that replicates hypereutrophic conditions in lakes and wastewater treatment plant eZuents and optimized the medium for silicon content. Cyclotella and Aulacoseira produced the highest levels of total lipids, 60 and 43 g total lipids/ml, respectively. Both diatoms are rich in fatty acids C14, C16, C16:1, C16:2,7,10, and C22:5n3. Of the diatoms examined, Cyclotella reached the highest population density (>2.5 £ 10 6 cells/ml) in stationary phase when many of the cells appeared to be Wlled entirely with oil. Silicon enrichment studies indicated that for optimal utilization of phosphorus and nitrogen by diatoms growing in wastewater eZuent, the amount of silicon present or added to the eZuent should be 17.5 times the mass of phosphorus in the eZuent. With high growth rates, high lipid contents, and rapid settling rates, Cyclotella and Aulacoseira are candidates for biodiesel production.

Biofuels from Diatoms: Potential and Challenges

BOOK CHAPTER, 2023

Biofuel is the hope of this planet to ensure safe and sustainable use amid increasing rate of pollution and global warming. The term biofuel may be misleading for some that it is only substitute of fossil fuels, which is not true. Biofuel is a broad term including bio-oil, biodiesel, bioethanol, biogas, etc. finding its use in transportation, cosmetics, cooking, nutrient supplements, etc. The generation of biofuel from diatoms is third-generation biofuel production. Either the lipid from diatoms is extracted as bio-oil or the whole biomass of diatoms is used as biocrude. Apart from the mainstream uses of biofuel, the diatom culture produces many by-products which find their use in multiple fields. The public authority of India reported Biofuels Policy in 2008 to advance its production and utilization. The main obstacle on the way is economic production of biofuel from diatoms, to make it worth choosing over other options. Diatoms grow fast but they produce lipids slow, and the process of extraction is even more tedious. However, with the use of recent technologies, proper management and planning, this method proves to be the most efficient and environment friendly way of biofuel production. Diatoms don't have a large number of cells in the body to support, they use carbon dioxide and other nutrients from waste, or eutrophied water bodies produce biofuel and clean their nearby environment in return. It is high time we develop this method to make it feasible for greater good.

A review on third-generation biofuels from marine diatoms

GSC Biological and Pharmaceutical Sciences, 2023

Modern life increases the consumption of fossil fuels leading to a decrease in natural resources. Therefore, an alternative energy sources like biowastes - food waste, agricultural waste, municipal waste, etc. energy tree sources like edible and non-edible oily seeds; and various aquatic plants were also identified as energy sources. In recent years, many efforts have been made to determine the possibility of using algae as a source of bio-oil and biogas for energy production. Algae are considered as large and diverse group, often autotrophic organisms, ranging from unicellular to multicellular. They can produce far greater amounts of biomass and lipids per hectare than any other type of terrestrial biomass-producing organism. Due to their global presence, diatoms are known for producer of biofuels in recent years. Another energy sources is biodiesel, which is used as a sustainable form of diesel fuel derived from natural sources. Diatomic biofuels are among the third generation bio...

Stress Induced Lipids Accumulation in Naviculoid Marine Diatoms for Bioenergy Application

International Journal of Biotechnology for Wellness Industries, 2015

Microalgae are expected to play promising role in the production of biofuel in current research. Two of marine diatoms, Navicula sp. and Amphora sp. were isolated and their growth rate was also studied. Total lipid content was analyzed in stationary growth state under normal conditions. By the two stage process, both the diatoms were subjected to nitrogen and silicon undersupplied for five days and the total lipid accumulation in the diatoms were found to be increased during nutrient deficiency period. The nutrient deficit conditions prone to increased total lipid content and also altered the fatty acid profile in diatom. The total lipid content of Navicula sp. and Amphora sp. were found to be 34.93% DCW and 41.10% DCW under normal conditions and in nitrogen deficiency conditions it has been increased to 60.71% DCW and 64.72% DCW respectively. The major fatty acids were found to be cis-10-Heptadecanoic acid (27.54%) and stearic acid (24.57%). The level of saturated and monounsaturated fatty acids were found to be high in both the diatoms. The presence of low level of polyunsaturated fatty acids indicated that these two organisms could find future application in bioenergy production.

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...

Diatoms: a fossil fuel of the future

Trends in Biotechnology, 2014

Long-term global climate change, caused by burning petroleum and other fossil fuels, has motivated an urgent need to develop renewable, carbon-neutral, economically viable alternatives to displace petroleum using existing infrastructure. Algal feedstocks are promising candidate replacements as a 'drop-in' fuel. Here, we focus on a specific algal taxon, diatoms, to become the fossil fuel of the future. We summarize past attempts to obtain suitable diatom strains, propose future directions for their genetic manipulation, and offer biotechnological pathways to improve yield. We calculate that the yields obtained by using diatoms as a production platform are theoretically sufficient to satisfy the total oil consumption of the US, using between 3 and 5% of its land area.

Current trends to comprehend lipid metabolism in diatoms

Progress in Lipid Research, 2018

Diatoms are the most dominant phytoplankton species in oceans and they continue to receive a great deal of attention because of their significant contributions in ecosystems and the environment. Due to triacylglycerol (TAG) profiles that are abundant in medium-chain fatty acids, diatoms have emerged to be better feed stocks for biofuel production, in comparison to the commonly studied green microalgal species (chlorophytes). Importantly, diatoms are also known for their high levels of the essential ω3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and are considered to be a promising alternative source of these components. The two most commonly exploited diatoms include Thalassiosira pseudonana and Phaeodactylum tricornutum. Although obvious similarities between diatoms and chlorophytes exist, there are some substantial differences in their lipid metabolism. This review provides an overview on lipid metabolism in diatoms, with P. tricornutum as the most explored model. Special emphasis is placed on the synthesis and incorporation of very long chain ω3 fatty acids into lipids. Furthermore, current approaches including genetic engineering and biotechnological methods aimed at improving and maximizing lipid production in P. tricornutum are also discussed.