Lactobacillus pentosus and Pichia membranifaciens, the dominant species in biofilms from natural green olives Gordal variety

Abstract

This work examines the microbial communities adhered to the epidermis of natural green olives, Gordal variety, in order to study the microbial biodiversity present in olive biofilms. The fermentation process was microbiologically monitored for 90 d. At this time, formation of true biofilms in the surface of fermented fruits was confirmed by scanning electron microscopy. Then, samples of olive fruits were withdrawn and treated by means of stomacher and sonication for biofilm disaggregation and subsequent recovery of the lactic acid bacteria and yeast populations. The use of the stomacher for 1 min was the most effective treatment to release the lactic acid bacteria from biofilms (6.6 log10 cfu·g-1), whereas sonication for 5 min was the most efficient method for recovery of yeasts (up to 3.5 log10 cfu·g-1). Molecular identification and characterization of isolates revealed that among lactic acid bacteria, Lactobacillus pentosus was the only species found, showing two different genotypes. In the other hand, Pichia membranifaciens was the predominant yeast species. A greater predisposition of the bacteria (due to their higher counts obtained) than the yeast for integration into these biofilms was noticed.