Health

Bacteria in Table Olives May Help Eliminate Heavy Metals During Digestion

The same genetic traits that allow the Lactobacillus pentosus bacteria to survive the table olive fermentation process may also help the microorganisms to bioquench and eliminate harmful heavy metals.

Lactobacillus pentosus bacteria under a microscope. Photo courtesy of the University of Jaén
Dec. 19, 2019
By Daniel Dawson
Lactobacillus pentosus bacteria under a microscope. Photo courtesy of the University of Jaén

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A group of researchers from the University of Jaén have iden­ti­fied a strain of bac­te­ria found in table olives that may help the human body to bio­quench heavy metals during diges­tion.

Lactobacillus pen­to­sus, the bac­te­ria respon­si­ble for the bio­quench­ing, is nat­u­rally occur­ring in the olive tree. Its pres­ence is ampli­fied during the fer­men­ta­tion process, through which table olives go in order to remove the nat­u­rally bitter taste of the fresh fruit.

These bac­te­ria act as a sponge that traps these types of par­ti­cles, reduc­ing their avail­abil­ity in the diges­tive system and elim­i­nat­ing them through feces.- Hikmate Abriouel, researcher at the University of Jaén

The researchers found that the bac­te­ria coats the lining of the intes­tine and pre­vents mol­e­cules of heavy metals, such as arsenic, cad­mium or mer­cury, from being digested and enter­ing the blood­stream.

All three of these heavy metals are known to be toxic to humans and are nearly impos­si­ble for the body to elim­i­nate once they have been absorbed.

See more: Olive Oil Health Benefits

“These bac­te­ria act as a sponge that traps these types of par­ti­cles, reduc­ing their avail­abil­ity in the diges­tive system and elim­i­nat­ing them through feces,” Hikmate Abriouel, one of the study’s authors and a researcher at the uni­ver­sity, said.

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While the Lactobacillus pen­to­sus bac­te­ria are nat­u­rally occur­ring, they become con­cen­trated during the fer­men­ta­tion process.

The lim­ited avail­abil­ity of nutri­ents, high salin­ity and low pH of the brine, along with the pres­ence of antimi­cro­bials, such as phe­no­lic com­pounds and oleu­ropein, cre­ates a harsh envi­ron­ment for bac­te­ria to sur­vive and repro­duce in.

However, the researchers dis­cov­ered that the Lactobacillus pen­to­sus bac­te­ria con­tains genes that allow it to sur­vive in the hos­tile brine envi­ron­ment, due to its abil­ity to metab­o­lize cer­tain car­bo­hy­drates and the unique struc­ture of the bacteria’s cell mem­branes.

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It is due to these adap­tive mech­a­nisms, the researchers con­cluded, that the bac­te­ria is also able to bio­quench the heavy metals.

“The bac­te­ria that allow these par­ti­cles to be retained are in the olive already in the tree,” Abriouel said. “When it under­goes fer­men­ta­tion, these microor­gan­isms pro­lif­er­ate because of their abil­ity to grow in an envi­ron­ment with low pH and also, as we have seen, in the pres­ence of these heavy metals, which they can trap.”

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The researchers also com­pared the abil­ity of the Lactobacillus pen­to­sus bac­te­ria to bio­quench the heavy metals both before and after having been fer­mented. They found that the bac­te­ria were far more effec­tive in doing so post-fer­men­ta­tion.

“In bac­te­ria, plas­mids [small DNA mol­e­cules within a cell that are sep­a­rated from the chro­mo­so­mal DNA] harbor an addi­tional genetic mate­r­ial present in the chro­mo­some, which are involved in var­i­ous processes such as resis­tance to pathogens or antibi­otics,” Abriouel said. “Fermentation allows these bac­te­ria to grow and in that habi­tat they express a series of genes, such as this one [that helps bio­quench the heavy metals], whose pur­pose is to allow it [the bac­te­ria] to exist and sub­sist in the envi­ron­ment.”

Indeed the researchers found that post-fer­men­ta­tion, the Lactobacillus pen­to­sus bac­te­ria expe­ri­ence a two to eight-fold increase in their abil­ity to bio­quench the heavy metals.

In the study, the researchers inves­ti­gated this process in the Aloreña vari­ety of olive, which has a Protected Designation of Origin (PDO) status from Malaga.

The researchers said they plan to con­tinue study­ing the Lactobacillus pen­to­sus bac­te­ria in other vari­eties of olives as well, in order to fur­ther under­stand its rela­tion­ship with heavy metals.

The results of their first study have been pub­lished in the jour­nal Nature.

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