Some uses of eukaryotic protists in other industries

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Eukaryotic protists are also used in technological applications. Once again the Eumycota are the main contributors. Their metabolic capacities are indeed widely used. Some of the secondary metabolites they make are colored and therefore have uses in dyeing. Lichens are highly valued as a source of natural pigments in shades of yellow, red, brown, beige… Lichens produce more than 600 secondary metabolites, of which more than 90% are specific to them. Besides their use in pharmacy and in dyeing, lichens are also used in perfumery. For example, Evernia prunastris (Figure 371), but also Pseudoevernia purpuracea, are collected in Mediterranean regions with the bark on which they grow. One to two percent essential oils are extracted and used in perfumes. They impart mossy odors and allow the perfume to hold better on the skin. Each year, around 10,000 tonnes of this raw material are harvested and used in the south of France.

The volatile organic compounds produced by fungi will likely be used in the future to produce clean energy. For example, Gliocladium roseum, an endophytic Leotiomycetes also known as Ascocoryne sarcoides, is able to synthesize a complex mixture of volatile eight-carbon molecules containing alkanes, alkenes, alcohols… Many Eumycota produce this type of molecules, but in much smaller quantities. Most of these compounds are present in kerosene and even if their production by Gliocladium roseum is done in very small quantities, the technological applications of this type of fungi for the manufacture of biofuel are obvious.

Other Eumycota like Agaricomycotina of the genus Trametes can produce methane aerobically or, like Neocallimastigomycota, hydrogen under anaerobic condition, two other clean energy sources. The redox properties of fungal enzymes such as laccases make them good candidates for replacing metals in fuel cells. These batteries generate electricity using oxidations of various substrates catalyzed by enzymes. They are still in the laboratory development stage, but their biodegradability makes them very attractive candidates for replacing batteries containing metals. Energy technologies are already using Eumycota fungi to produce first and second generation biofuels, as well as eukaryotic microalgae to produce third generation biofuels (Box 32).

The enzymes used by fungi to break down plant biomass are also of interest to industries other than biofuel production. They are of great interest to the paper industry with the aim of obtaining non-polluting bio-processes for bleaching paper. Likewise, the enzymes involved in the degradation of lignin are active with respect to other polluting compounds such as dyes, polyphenols, etc. The Eumycota are therefore the subject of a bioremediation feasibility study to decontaminate soil or water. They are indeed able to overcome difficult to break down phenolic compounds, plastics and other xenobiotic compounds. Their cell walls fix heavy metals and can be used to purify water. Microalgae, especially Viridiplantae microalgae, can be used to purify eutrophic waters rich in phosphates or nitrates, such as those at the end of purification in stations. The produced algal biomass can then be used for various purposes such as the production of fertilizers, fatty acids, vitamins, etc.

Yeasts are often used to produce enzymes or metabolites of pharmaceutical, agrifood or other interest. In most cases, they are genetically modified to obtain the desired product. They can also be adapted in the same way to use carbon sources less expensive than hexoses, such as, for example, pentoses present in large quantities in plant biomass and often not used. For example, Saccharomyces cerevisiae has been modified to produce insulin, glucagon, the hepatitis virus surface antigen for vaccination, hirudin which is an anticoagulant factor, vitamins, sterols and steroids. Yarrowia lipolytica, another Saccharomycotina, is used in the production of lipases, flavors, organic acids, bio-surfactants, emulsifiers… Other Saccharomycotina are also frequently used, like the species of the genus Pichia, to produce various enzymes that are for example added to the cocktail produced by Trichoderma reesei to make second generation bio-fuels (Box 32). Compared to bacterial models of protein expression, yeasts have the advantage of making post-translational modifications to proteins, which often improves their activity or stability and decreases their immunogenic potential.

The applications of eukaryotic protists are therefore already numerous and varied. As additional example, we can cite diatomite from Bacillariophyta and whose uses are multiple (see pages 319 & 320), packaging based on waste agglomerated by fungi such as “mycoboard” or biosensors based on algae. These biosensors make it possible to assess water pollution by measuring the activity of algae immobilized in gels. For this, their photosynthetic activity is quantified by measuring the fluorescence of chlorophylls or the production of oxygen. The use of algae sensitive to different types of pollution makes it possible to refine the diagnosis. Note that lichens have long served as bioindicators of air pollution. Indeed, they are sensitive to pollution and their presence in good health indicates clean air (Figure 372). The more the air quality deteriorates, the more they deteriorate and disappear, the most sensitive species such as Evernia, Parmelia or Usnea disappearing first, and then the more resistant species such as Xanthoria or Lecanora which tolerate nitrates well. The different present species give an idea of the level and nature of the pollutants present in the air. In highly polluted environments, such as our city centers, there is generally only Chlorophyta algae of the genus Pleurococcus (Figure 372) on the structures usually colonized by lichens… Eukaryotic protists will probably be even more involved in the future, where sustainable and non-polluting technologies based on biomimicry will probably be favored to the detriment of current technologies which are often polluting.

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