Lysozyme resistance of the ropy strain Pediococcus parvulus IOEB 8801 is correlated with beta-glucan accumulation around the cell

Lactic acid bacteria (LAB) are often exploited to carry out malolactic fermentation in wine. However, a few specific LAB strains and, more precisely, some Pediococcus parvulus strains synthesize a β-glucan, which can be deleterious to wine quality as it confers a ropy texture to the wine that can no longer be commercialized. Although molecular methods exist to detect these unwanted microorganisms, ropy Pediococcus still remain difficult to remove from wine, because of their natural resistance to traditional wine stabilizing treatments. In this work, we show that ropy P. parvulus are resistant to lysozyme. We clearly demonstrate that this resistance may be ascribed to the presence of the β-glucan that forms around the cell a protective barrier against anti-bacteria agents. Moreover, this resistance increases during bacterial growth. We show that using lysozyme with β-glucanase can strongly improve the treatment against ropy strains, in model media as well as red and white wine based media. This work not only brings potential solutions to the wine industry, but also opens interesting perspectives for studying β-glucan producing bacteria which are widespread in the food industry.

► Ropy Pediococcus parvulus from wine is highly resistant to oenological lysozyme.
► Resistance is due to the presence of a coat of beta-glucan around the cells.
► This coat size varies during growth.
► This coat can be efficiently removed by using beta-glucanase.
► The association of lysozyme and beta-glucanase enables to eliminate ropy pediococci.