Like every bioeconomy sector, the industries around biobased chemicals and biomaterials depend on the living world. Certain species hold immense importance in biobased supply chains – particularly crop species that are usually destined for human food. Among the most important is corn, which makes up 80% of current bio-based plastics.
However, there is controversy around using land crops as raw materials for biomanufacturing. Large-scale farms compete with food and conservation for land, increase water pollution, and draw on carbon-intensive fertilisers. This is leading more biobased actors to explore alternative organisms that generate competitive biomass volumes with a smaller resource footprint.
In this article, we detail the ‘keystone’ species that could underpin a more land-efficient, lower-carbon biobased chemical industry.
Green algae: C. reinhardtii
Algae, including seaweed, overcomes many problems with both fossil and crop-based feedstocks. Seaweeds and algae more generally require fewer inputs than conventional bioeconomy feedstocks like corn. They are also capable of achieving much faster and year-round growth.
These marine organisms are broadly divided into green, red, and brown algae. each group known for distinctive properties that are useful to industry.
Green seaweeds are the ancestors of land plants and evolved around 1.3 billion years ago from simpler diatoms. There are over 1800 species that belong to the green seaweed category and many are already used for food and chemicals worldwide.
One of the most coveted chemicals concentrated inside green seaweeds is ulva, a complex acidic polysaccharide, which has cosmetic and medical applications. Green seaweeds have also been used as biofertiliser, in animal feed, and wastewater treatment.
One species that researchers believe have high industrial potential is the one-cell green microalgae c. reinhardtii. Specifically, they believe that it could be used as a ‘industrial biotechnology platform’. Its metabolism can be engineered so that the species feeds on simpler compounds and outputs complex, consistent chemical products ready to be harvested, processed, and sold on. These organisms reproduce quickly, a key criteria for industrial relevance.
C. reinhardtii’s genetic and metabolic properties have been widely-studied, giving it a headstart in the road to achieving commercial importance. More than 100 different proteins have been produced inside the c. reinhardtii chloroplast – the part of the microorganism that seems to be the most efficient protein factory and the easiest to genetically manipulate.
Already, China has approved C. reinhardtii as a new raw material for food products and microalgae companies around the world have derived microalgae powder, oils like the fatty acid EPA and DHA, and pigments from the species.
Another use for the species – as well as certain other green algae – is as a biological wastewater clean up tool, especially for fertiliser-rich agricultural wastewater. They are placed in tanks of run-off from farms, where they absorb nutrients like nitrogen and phosphorus, concentrating the elements. From there, their nutrient-rich bodies are taken out of the water and used to fertilise fields. Using algae to collect and reuse waste fertiliser means farmers cut back on the use of virgin soil inputs and that less polluted water reaches the river system.
Mostly, the use of algae as a wastewater treatment remains in its early stages. The King Abdullah University of Science and Technology (KAUST) in Saudi Arabia trialled the use of c. reinhardtii as a wastewater treatment successfully in December 2023 at a demo-scale plant in Jeddah. The team found that the algae consumed 100% of nitrogen and phosphorus from the wastewater at different conventions, showing its potential for larger-scale use.
Red algae: the Gelidium genus
The most diverse type of algae are the red algae, with almost 6,000 species in the oceans.
The most industrially important compounds in these organisms are carrageenan and agar, thickening agents that are used in textile, food, and laboratory-grade bacterial growth cultures. Researchers are now seeing what other uses it might hold in pharmaceuticals, cosmetics, food supplements, biomaterials, and biofertilisers.
Gelidium amansii is one red algae species gaining attention as a bioeconomy feedstock, including as a source for bioethanol. It has a high carbohydrate content which makes it ideal for conversion into simple sugars that can be fermented into fuel. However, seaweed biofuel commercialisation remains distant as this feedstock requires different harvesting, pre-treatment, hydrolysis, and fermentation techniques to produce from land-based crops like corn.
The closely related species Geldium corneum also contains compounds that could offer a less polluting biobased sunscreen than the mineral or fossil based options that dominate the market today. The algae has mycosporine-like amino acids (MAAs) shinorine, P334, palythine, asterina, and palythinol that absorb ultraviolet radiation. MAAs also protect from sun damage with its antioxidant capacity.
Researchers at the University of Minho in Portugal found that weaving UV-protective nanoparticles with Gelidium corneum extracts into cotton and polyester can create fabrics that protect against damaging rays.
Yeast
Yeasts, particularly the species Saccharomyces cerevisiae, is a hugely important organism in the bioeconomy. These single-celled fungi are used to manufacture many different biomolecules for a wide range of industries including biofuel, biodiesel, food, and complex biochemicals.
The importance of yeast as a living biofactory lies in how versatile it is. In theory, it can be genetically manipulated to process almost any kind of organic matter into new chemicals. In 2022, researchers published a paper investigating how strains could turn wastewater from the Tequila industry in Mexico into high-quality animal feed and supplements.
Although widely used already throughout the bioeconomy, yeasts harbour much more genetic potential. At the moment, only a small sliver of the group have been exploited but other yeast genuses like candida, starmerella, Kluyveromyces, and Lachancea could offer new chemicals from hard-to-valorise feedstocks.
Researchers are also now beginning to develop ways of using waste from the yeast biomanufacturing process itself to create higher value goods. Spent brewery yeast could be used to make more sustainable fishmeal, given its high protein content.
Filamentous fungi
Filamentous fungi are already used in industry. 82% of the enzymes for food and beverage manufacturing derive from this diverse class of species.
However, like yeasts, these microorganisms could also help expand the circular bioeconomy due to their ability to turn waste into valuable chemicals. Two properties mark them out as cost-effective biomanufacturing tools: they can feed on a broad range of materials and can survive in diverse growth environments.
For example, filamentous fungi could crack the cost issue in valorising wood waste. At the moment, turning wood waste into higher value chemicals entails a complicated process of pretreatment, which aims to remove the target chemical lignin from the woody matter.
Unfortunately, lignin is so well embedded into the structure of wood that this is difficult to achieve. It also requires pure enzymes that are expensive. Currently, industries use a combination of thermochemical and biological pretreatment and processing.
Filamentous fungi secrete special enzymes that could make the process of extracting lignin far easier. Biorefineries operations could become more cost-competitive as a result, able to draw on cheap, low-value wood waste using an efficient, living chemical stripper.
Of course, biomanufacturing is a complex and multi-step process. It is likely that no single species would be able to perform all of them, particularly if the biorefinery outputs various chemical products. However, combining strains could work.
As well as offering a new biomanufacturing tool, filamentous fungi also contain a wide range of chemicals that could themselves be extracted and sold on as: vitamins, fibre, protein, and pigments. The potential end sectors for these chemicals are as diverse as those for petrochemicals, covering food, feed, fuels, biochemicals, and biopolymers.
The use of filamentous fungi applied to wood waste is still in its testing stages but some results have been promising. The companies DSM and Roquette managed to create succinic acid from wood waste using the microorganisms. These acids are used in a range of industries to make polymers, clothing fibres, plasticisers, solvents, paints, inks, food and feed additives, pharmaceuticals, perfumes, and an array of industrial and consumer products. Their life cycle analysis indicated that the fungi process emitted half of the greenhouse gases that conventional chemical production creates.
Biodiversity in the bioeconomy
The last twenty years has seen rising interest in new biobased manufacturing technologies. Policymakers and industry see biobased goods as potential replacements for non-renewable mined inputs like petrochemicals or carbon-intensive farmed livestock. Bioplastics, biofuels, novel food ingredients, and biochemicals are singled out as goods that can help economies decarbonise.
One guardrail in ensuring the sustainability of the bioeconomy is for the industries within it to extend the range of species they are utilising. If biobased industries lean too heavily on a few types of feedstock, it can run the risk of damaging biodiversity. This is a risk that applies to the offshore cultivation of seaweed, where large monocultural farms could upset the coastal ecosystem.
Microorganisms that can valorise various types of organic waste is a good way to achieve this. As well as a potentially lower land footprint, fungi and microalgae have the metabolic capabilities to transform waste feedstocks already being produced in high volumes. R&D into the chemical capabilities of new biomanufacturing species could unlock more recalcitrant feedstocks like forestry waste, opening a bigger and more sustainable raw materials supply.
