Bacteria in Table Olives May Help Eliminate Heavy Metals During Digestion

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.

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.

“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.

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.

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.”

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.

• University of Jaén News


• Nature