`Yeast Study Finds Solution for Olive Mill Wastewater Treatment - Olive Oil Times
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Yeast Study Finds Solution for Olive Mill Wastewater Treatment

By Simon Roots
Jun. 25, 2025 13:52 UTC
Summary Summary

A study in the jour­nal Fermentation explores the use of Yarrowia lipoly­t­ica yeast to con­vert olive mill waste­water into valu­able com­pounds for var­i­ous indus­tries, address­ing the issue of waste­water pol­lu­tion in the olive oil indus­try. While the yeast shows promise, chal­lenges such as waste­water vari­abil­ity, com­pound inter­fer­ence, and eco­nomic fac­tors must be addressed for wide­spread imple­men­ta­tion in treat­ing and uti­liz­ing olive mill waste­water effec­tively.

A new study, pub­lished in the jour­nal Fermentation, has exam­ined the use of the non-con­ven­tional yeast Yarrowia lipoly­t­ica to con­vert olive mill waste­water into high-value com­pounds with appli­ca­tions across a wide range of indus­tries, includ­ing bio­fuel, food and phar­ma­ceu­ti­cals.

The olive oil indus­try gen­er­ates a sub­stan­tial amount of waste­water, with esti­mates exceed­ing 30 bil­lion liters per annum world­wide. 

This water is a potent and prob­lem­atic pol­lu­tant, char­ac­ter­ized by high salin­ity and elec­tri­cal con­duc­tiv­ity, as well as high acid­ity and large quan­ti­ties of organic and phe­no­lic com­pounds.

See Also:Study Finds Potential for Olive Mill Wastewater in Biopesticides

These char­ac­ter­is­tics make it harm­ful to soil microbes, aquatic life and long-term soil health. Phenolic com­pounds, in par­tic­u­lar, con­tribute to the waste­water’s resis­tance to treat­ment, inhibit­ing micro­bial growth.

The vast major­ity of olive mill waste­water is cur­rently dis­posed of in one of two ways. The first is via evap­o­ra­tion ponds, which lead to increased air pol­lu­tion due to the release of harm­ful and acidic gases such as methane and hydro­gen sul­fide, and both soil and ground­wa­ter con­t­a­m­i­na­tion due to leach­ing.

The sec­ond is via its use as an organic fer­til­izer on agri­cul­tural land. However, there is also grow­ing con­cern about this prac­tice. 

Studies have shown that pro­longed and repeated land appli­ca­tion leads to the accu­mu­la­tion of phe­no­lic com­pounds, salts and heavy met­als in soils, reduced micro­bial diver­sity and activ­ity, wide­spread impacts on wildlife and the even­tual ster­il­iza­tion and deser­ti­fi­ca­tion of land.

Several micro­bial organ­isms have been pro­posed as can­di­dates for treat­ing olive mill waste­water. Of these, the researchers believe that Yarrowia lipoly­t­ica stands out, not only due to its abil­ity to thrive in nutri­ent-poor, acidic, phe­no­lic-rich envi­ron­ments, but also because of the range of valu­able sub­stances it can pro­duce.

Among other com­pounds, the yeast can syn­the­size lipases, impor­tant in sec­tors such as food pro­cess­ing, phar­ma­ceu­ti­cals and bio­fu­els; cit­ric acid, used in indus­tries as diverse as deter­gent man­u­fac­tur­ing, elec­tro­plat­ing and leather tan­ning; and poly­ols, includ­ing man­ni­tol, ery­thri­tol and ara­bitol, which have appli­ca­tions in prod­ucts such as low-calo­rie sweet­en­ers and humec­tants.

The yeast also syn­the­sizes sin­gle-cell oils, rich in oleic and linoleic acids, which are suit­able for use as biodiesel or as nutri­tional sup­ple­ments. 

By mod­u­lat­ing cul­ture con­di­tions such as oxy­gen lev­els, pH and car­bon source, pro­duc­tion can be tai­lored to dif­fer­ent end uses. The result­ing lipid pro­files can even mimic cocoa but­ter or serve as pre­cur­sors for rici­noleic acid deriv­a­tives with diverse appli­ca­tions.

See Also:Producers in Greece Generate Electricity with Olive Mill Wastewater

The research team empha­sizes that these capa­bil­i­ties mean the process of waste­water treat­ment can con­tribute to the move towards a cir­cu­lar econ­omy within the olive oil indus­try, a move sup­ported not only by the sci­en­tific com­mu­nity but also by national and supra­na­tional gov­ern­ment bod­ies, such as the European Union.

Despite its promise, the wide­spread deploy­ment of Y. lipoly­t­ica for olive mill waste­water treat­ment and val­oriza­tion faces sev­eral obsta­cles. 

Wastewater com­po­si­tion is highly vari­able, influ­enced by fac­tors such as olive vari­ety, extrac­tion method and sea­sonal con­di­tions, among oth­ers. This vari­abil­ity com­pli­cates process stan­dard­iza­tion and per­for­mance.

In addi­tion, com­pounds, par­tic­u­larly phe­no­lics and salts, can reduce micro­bial activ­ity or prod­uct yields. While some strains tol­er­ate these con­di­tions, oth­ers require dilu­tion, pre-treat­ment or sup­ple­men­ta­tion to main­tain effi­ciency.

Economic fac­tors also pose bar­ri­ers. Although Y. lipoly­t­ica can grow in non-ster­ile, low-cost media, large-scale oper­a­tions require sys­tems with high-energy stages, down­stream pro­cess­ing and mar­ket access for bio-based prod­ucts.

However, the researchers believe that with suf­fi­cient research focused on key areas, the yeast rep­re­sents an eco­nom­i­cally viable way to unlock the poten­tial of olive mill waste­water whilst safely remov­ing it from the envi­ron­ment. 

They point to proof-of-con­cept stud­ies and a con­sid­er­able body of exist­ing lit­er­a­ture to sup­port this view.

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