Tag Archives: #microalgae

Scientists Program Microalgae’s ‘Oil Factory’ to Produce Various Oils (Biology)

By combining the ‘chassis’ of an oil-producing microalgae with genes from a Cuphea plant, scientists from Single-Cell Center, Qingdao Institute of BioEnergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS), can turn the algae into a microbial cell factory that can produce various oils with different properties. 

The study was published in Metabolic Engineering on April 3. 

Oils are composed of fatty acids, and fatty acids are composed in part of chains of carbon atoms. The length of these carbon chains can impact the physical properties of the fatty acid and thus the property of the oil. The researchers now can program the algal ‘factory’ by designing the algae to produce fatty acids of different lengths. 

Oleaginous microalgae are often attractive candidates as “cell factories” due to their rapid reproduction rates and ability to produce large volumes of fatty acids. 

But the chain-length of the fatty acids produced by these self-replicating photosynthetic factories is very rigidly specific to a given species. Typically, one type of microalgae would be great at producing fatty acids of some lengths, but not others. 

In microalgae, fatty acids are synthesized by a particular type of enzyme, called the fatty acid synthase, or FAS. And the chain length of these fatty acids is in turn determined by the action of another type of enzyme, called an Acyl-ACP thioesterase, or simply a TE. Different types of TEs from different species specialize in different chain lengths. 

“This is far from ideal as a product-flexible cell factory to deliver the plethora of chain lengths needed at will for various industrially relevant fatty acids, as you would have to constantly swap out the species that is doing the producing,” said WANG Qintao, a researcher at Single-Cell Center, the first author of the study. 

However, the research team found that the microalgae Nannochloropsis oceanica (N. oceanica) had a TE enzyme pathway that can vary the chain length to produce three variations on some of the longer fatty acids, but can’t vary the chain length to produce multiple mid-length fatty acids. 

So they added the genes for a similar TE enzyme pathway from a Cuphea plant – one that was good at boosting production of fatty acids with those mid-length chains. Protein engineers led by FENG Yanbin and XUE Song, now at Dalian University of Technology, tuned the enzymes so that fatty acids of a different chain length can be produced. The Cuphea genus is home to many species of plants also known for their oil production capabilities. 

But by combining the enzymes, the team showed that it was possible to ratchet the fatty acid chain up and down a broad range of desired lengths, and within the N. oceanica ‘factory’. 

The researchers hope that this basic framework will now accelerate the development of designer oils of various fatty acid chain lengths within other species of Nannochloropsis and other oleaginous microalgae. 

“By directly turning CO2, sunlight and seawater into designer oils, such microalgae cell factories are carbon negative, thus farming them at a large scale can help to save our planet from global warming,” added XU Jian, Director of Single-Cell Center, and one senior author of the study.

Featured image: In the engineered microalgal oil factory, length of fatty acid molecules can be tuned at will, just like the golden cudgel of Monkey King. (Image by LIU Yang and WANG Qintao) 

Reference: Qintao Wang, Yanbin Feng, Yandu Lu, Yi Xin, Chen Shen, Li Wei, Yuxue Liu, Nana Lv, Xuefeng Du, Wenqiang Zhu, Byeong-ryool Jeong, Song Xue, Jian Xu, Manipulating fatty-acid profile at unit chain-length resolution in the model industrial oleaginous microalgae Nannochloropsis, Metabolic Engineering, 2021, , ISSN 1096-7176, https://doi.org/10.1016/j.ymben.2021.03.015. (https://www.sciencedirect.com/science/article/pii/S1096717621000513)


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Genome Scalpel Invented for Industrial Microalgae to Efficiently Turn CO2 into Biofuel (Botany)

A single-celled alga undergoes genome surgery to remove non-essential parts. This can lead to a most efficient cellular factory for producing sustainable biofuels from sunlight and carbon dioxide. 

Researchers from the Qingdao Institute of BioEnergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) have stripped hundred-kilobase genome from a type of oil-producing microalgae, knocking out genes non-essential for it to function. By doing so, they have created a “genome scalpel” that can trim microalgal genomes rapidly and creatively.

The ‘minimal genome’ microalgae produced is potentially useful as a model organism for further study of the molecular and biological function of every gene, or as a ‘chassis’ strain for synthetic biologists to augment for customized production of biomolecules such as biofuels or bioplastics.

The study was published in The Plant Journal on March 14, 2021. 

Creation of a ‘minimal genome’ — a genome stripped of all duplicated or apparently non-functional ‘junk genes’ — can be very useful for investigating fundamental questions about genetic function and for designing cell factories that produce valuable compounds.

Such minimal genomes have been created for simple organisms, but rarely for eukaryotic organisms, including algae or plants. In higher eukaryotes, “junk” regions can take up to 70 percent of the genome. Deleting what only appears to be “junk genes” in fact can have harmful effects on the organism or even kill it. 

For the first time, researchers from QIBEBT have produced a genome with targeted deletions, of hundred kilobases in size each, for a type of algae called Nannochloropsis oceanica

N. oceanica are microalgae (single-celled algae) that have tremendous potential for production of biofuels, biomaterials and other platform chemicals in a renewable and sustainable manner while reducing greenhouse gas emissions. However, realizing the potential of these microalgae requires extensive genetic engineering of the organism to maximize yields and minimize production costs. 

The QIBEBT team first identified the non-essential chromosomal regions — ones whose genes were rarely expressed, or activated. They identified ten such ‘low-expression regions’, or LERs. They then used CRISPR-Cas9 gene-editing technique to snip out two of the largest LERs — over 200 kilobases in size. 

“Despite the all snipping, the microalgae still showed essentially normal growth, lipid content, fatty acid saturation levels and photosynthesis,” said study first-author WANG Qintao, of the Single-Cell Center (SCC) in the QIBEBT. “In some cases, there was even a slightly higher growth rate and biomass productivity than the organism in the wild.” 

“We interestingly found normal telomeres in the telomere-deletion mutants of Chromosome 30,” said the corresponding author XU Jian, of the SCC in QIBEBT. “This phenomenon implies the losing of distal part of chromosome may induce telomere regeneration.” 

Already, the substantially snipped genome should serve as a closer-to-minimal genome in Nannochloropsis, which can serve as the chassis strain for customized production of biomolecules using further metabolic engineering atop this chassis.  

Now that they have proven they can strip down the genome of such a complex eukaryote, the researchers now want to see if they can snip out still further LERs and other non-lethal regions, to craft a fully minimal Nannochloropsis that makes biofuels from CO2 with the highest efficiency. 

Featured image: Hundred-kilobase fragment deletions in microalgae by Cas9 cleavages. This figure was made using BioRender. (Image by LIU Yang)


Reference

Genome engineering of Nannochloropsis with hundred‐kilobase fragment deletions by Cas9 cleavages


Provided by Chinese Academy of Sciences

Biotechnologists Developed an Effective Technology For Nutrient Biocapture From Wastewater (Biology)

Biotechnologists from RUDN University in collaboration with Lomonosov MSU and Kurchatov institute made an important contribution to the technology of phosphate and nitrate biocapture from wastewater using Lobosphaera algae fixed on the filters.The biomass obtained in the course of this process can be used as a fertilizer. The results of the study were published in the Journal of Water Process Engineering.

Phosphates and nitrates get to the wastewater together with industrial and household waste, especially detergents. Both substances are parts of phosphorus and nitrogen chemical cycles. However, these cycles are disturbed by human activity, as the growing amounts of phosphates and nitrates cannot be processed by water ecosystems. As a result, these substances turn from useful nutrients to pollutants. Wastewater is treated with special equipment and microorganisms, including microalgae that consume phosphates and nitrates. A team of biotechnologists from RUDN University together with their colleagues from MSU and the Kurchatov Institute developed a biopolymer filter on which useful microalgae can be placed. The polymer is chitosan-based, safe for the algae, biodegradable, and captures chemical elements from wastewater more effectively than its existing analogs.

“Our team was the first to successfully use cross-linked chitosan polymers to immobilize unicellular algae and make them effectively consume nutrients while at the same time not preventing them from growing and photosynthesizing,” said Alexei Solovchenko, a PhD in Biology from the Department of Agrobiotechnology, RUDN University.

Chitosan is a polysaccharide with amino groups and its chemical composition is similar to that of chitin that can be found in shellfish crusts and mushroom cell walls. Chitosan is not water-soluble and therefore can be used to grow algae. However, it is biodegradable. Using an original methodology developed in the Kurchatov Institute, it was cross-linked with glutaraldehyde molecules and thus turned into a strong biocompatible polymer. Then, the team grew the IPPAS C-2047 strain of the Lobosphaera incisa algae on it for seven days.

Based on the results of the seven-day long experiment, the team concluded that a complex of microalgae cells and chitosan-based polymer with a total molecular mass of 600 kDa was more effective than that with a molecular mass of 250 kDa. The algae on the filter captured the nutrients more efficiently than those suspended in the wastewater: specifically, they consumed phosphates 16.7 times and nitrates 1.3 times faster.

Used chitosan biofilters could be repurposed as fertilizers. With time, chitosan would degrade without causing any harm to the environment, while the algae would act as a source of accumulated phosphates and nitrates for the plants.

“Our team has demonstrated that cross-linked chitosan polymers are safe for the environment and effectively support the biocapture of nutrients from wastewater by unicellular algae. When added to a non-toxic medium, the algae biomass could be used as a fertilizer that would gradually release the accumulated nutrients into the soil,” added Alexei Solovchenko from RUDN University.

Featured image: Biotechnologists from RUDN University in collaboration with Lomonosov MSU and Kurchatov institute made an important contribution to the technology of phosphate and nitrate biocapture from wastewater using Lobosphaera algae fixed on the filters.The biomass obtained in the course of this process can be used as a fertilizer. © RUDN University


Reference: Svetlana Vasilieva, Elena Lobakova, Timofey Grigoriev, Irina Selyakh, Larisa Semenova, Olga Chivkunova, Pavel Gotovtsev, Christina Antipova, Yuri Zagoskin, Pavel Scherbakov, Alexander Lukyanov, Ksenia Lukanina, Alexei Solovchenko, Bio-inspired materials for nutrient biocapture from wastewater: Microalgal cells immobilized on chitosan-based carriers, Journal of Water Process Engineering, 2020, 101774, ISSN 2214-7144, https://doi.org/10.1016/j.jwpe.2020.101774. (https://www.sciencedirect.com/science/article/pii/S2214714420306516)


Provided by RUDN University