Exploring the Applications of Diatoms in Biotechnology
Wimansa Wijesinghe
UG | Biotechnologist | Article Writer | Former Editor at Tree For Life | Brand Ambassador of The Sri Lankan Scientist Magazine at Wayamba University of Sri Lanka | Rotaractor | Volunteer | Content Creator | Innovator
Diatoms are a dynamic type of microorganism with rich diversity due to their detailed membrane design. They are the most dominant phytoplankton, with an overall number of around 200,000 species and they having a complex variability in dimensions and shapes. Typically, diatoms are unicellular and photosynthetic microalgae widely distributed in freshwater, seawater, and even wet soils, ranging from 2 μm to 2 mm in size with thousands of different morphologies.
Diatoms have a distinct silica cell wall, known as a frustule, which differentiates them from other phytoplankton communities. These frustules are made from biosilica, and they self-assembled into intricate porous shells that feature unique properties, including high specific surface area, biocompatibility, tailorable surface chemistry, thermal stability, and high mechanical and chemical resistance.
The studies on diatom biotechnology have rapidly increased in the past 10 years. Therefore, diatoms are useful in numerous applications in biotechnology, such as biofuel production, biomedical applications, nutraceuticals in the food industry, biosensors, nanomaterials & nanoparticles, and phytoremediation in environmental biotechnology.
Diatoms in Biofuel Production
In the biofuel industry, diatoms can be used as feedstock to replace non-renewable sources of energy. Because geochemists have proven that algal lipids are the major feedstock of petroleum and diatoms have the potential to accumulate high lipids and varied compositions of fatty acids. Therefore, diatoms are considered an underexploited area of biofuel production.
Diatoms in Biomedical Industry
Since current drug delivery systems have limited solubility, poor bio-distribution, lack of selectivity, premature degradation, and unfavorable pharmacokinetics, researchers tend to find alternative drug delivery systems to improve the performance of drugs.
In here, the intricate frustule characteristics of diatoms, including consistent pore structure, chemical inertness and biocompatibility, non-toxicity, ease of transportation, filtration efficiency, and targeted drug delivery, have created an attracted attention for its use in drug delivery. And also, 3D section analyses of diatom frustules have shown the availability of multiple pore patterns that range from nanometer to micrometer and diatoms’ frustule structure changes its homogenous nature, space, and intricate nature according to various environmental factors and silicon uptake efficiency. These features involve diatoms to be used in various biomedical and nanotechnological applications.
Some diatom species, such as Coscinodiscus concinnus spp. and Thalassiosira weissflogii spp., are considered potential drug carrier candidates due to their amorphous nature and morphology. And also, some research has shown that diatom microcapsules act as effective carriers for poorly soluble & water-soluble drugs, which can be applied in both oral and implant applications. In addition to those, the concept of employing biosilica derived from diatoms as intelligent support for cell growth is supported by the observation of fibroblast and osteoblast proliferation on functionalized frustules. Furthermore, the application of genetically modified biosilica has allowed for the targeted delivery of anticancer medications to tumor locations.
Biosensors, Nanomaterials & Nanoparticles
Advances in biotechnological tools enable characterization of diatom frustules for optoelectronic fabrication. Some diatoms' uptake of elements like zinc and germanium alters pore size, shape, and characteristics, benefiting paleolimnological indicators and photonic device applications.
Furthermore, diatoms' nano-biochemical machinery can create various nanostructures with diverse optical and electronic properties, leading to their use in biosensing. The incorporation of chemical elements like germanium affects the structure and size of frustule pores. A study tested the use of Si-Germanium composite material in living diatoms, reducing pore size without disrupting morphology.
And also, Germanium insertion in Nitzschia frustulum creates nano-comb structures with blue photoluminescence, it is suitable for semiconductors and optoelectronics. Combining these materials with silica frustule enhances durability and applications in nanotechnology industries. These lab-scale discoveries demonstrate the potential of creating advanced nanomaterials in living diatoms.
Researchers are focusing on the development of advanced, eco-friendly nanoparticles for various applications, including antimicrobial activity, catalyst development, waste and chemical compound filtering, and biosynthesis of metallic nanoparticles in photoautotrophic organisms. According to recent reports, diatoms have the ability to biosynthesize silver and gold nanoparticles, which showed potent cytotoxicity against pathogenic microbes.
Diatoms in Phytoremediation
There is some research on microalgae's potential use together with both small- and large-scale companies for wastewater treatment that has been ongoing for a while. Diatoms can gain nutrients from an excess of industrial waste discharged into the aquatic ecosystem. Recent studies have shown that diatoms can be used to treat wastewater with less damage to the environment.
One of the main issues caused by the companies that use chemicals and dyes is heavy metal contamination. Since diatom species are easily exposed to, absorb, and detoxify metal ions by single cells, they are ideal organisms to study heavy metal pollution. Diatoms and microalgae undergo a special detoxification process because of metal-binding peptides called phytochelatins (PCs), which shield photosynthetic organisms from heavy metals. And also, some diatoms can degrade phenol compounds. Furthermore, during the metabolism of phenanthrene and pyrene in diatoms, simple enzymatic oxidation has been found to degrade harmful molecules such as phenylalanine hydroxylase into less dangerous chemicals. However, there are not plenty of studies on applying diatoms' potential to biodegrade waste materials.
Diatoms as Nutraceuticals in Food Industry
Diatoms are extremely nutritious and can be used to create novel substances, including vitamins, antioxidants, animal feed, and supplements of vegetarian protein. Diatoms have been found to contain a number of photosynthetic pigments, including carotenoids like fucoxanthin. Furthermore, EPA and DHA can be found in significant amounts in the extracts of Nitzschia laevis, Nitzschia inconspicua, Navicula saprophila, and Phaeodactylum tricornutum, which can be used as a nutritious feed in human diets and animal diets.
And also, diatoms produce unsaturated fatty acids like eicosapentaenoic acid (EPA, 3.9-5% of dry weight in Phaeodactylum tricornutum), arachidonic acid, doco-sahexaenoic acid, and other omega-3 fatty acids. Typically, they are found in 20% of the brain's grey matter, lower cardiovascular disease, act as precursors for significant tissue hormones, and are generally believed to have anticarcinogenic properties.
Future of Diatoms in Biotechnology
In addition to the above applications, artificially synthesized substances like antibodies, vaccines, hormones, and enzymes are currently produced in bacteria, yeast, and mammalian cell cultures, which have disadvantages like toxins, viruses, and cost. Plants have been used to circumvent these disadvantages but have transgenic pollen, potentially leading to unwanted genetic modifications and competing for land plots. Diatoms have the potential to compartmentalize transgenetic processes, allowing biochemical precursors to be synthesized in one compartment and processed in another. Asexual growth and closed fermentation can avoid these issues.
Synthetic biology innovations may contribute to the large-scale production of high-value substances, such medicines, industrial enzymes, or bioactive chemicals, by genetically modifying diatoms. This field has the potential to develop more sustainable and effective production techniques for a range of businesses. Diatoms, in contrast to other microalgae, have had limited biotechnological use. This is probably because of challenges with their cultivation.
However, a lot of research is being carried out to employ diatoms in many biotechnological applications. As a result, diatoms have an exciting future in biotechnology, with applications ranging from materials research and environmental protection to healthcare. Due to their inherent qualities as well as developments in synthetic biology and genetic engineering, diatoms are expected to be important components of several biotechnological advancements.
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Article by,
Wimansa Wijesinghe