Pediocin PD-1 as a Method to Control Growth ofOenococcus oeniin Wine

Abstract

While malolactic bacteria are known to stabilize wine and change its organoleptic properties, uncontrolled malolactic fermentation may cause spoilage. Use of SO₂ to inhibit microbial growth is strictly regulated, and demands for safe alternatives to chemical preservatives has led to increased interest in natural antimicrobial substances. Pediocin PD-1, an antimicrobial peptide produced by <i>Pediococcus damnosus</i> NCFB 1832, is active against a number of lactic acid bacteria, including malolactic strains of <i>Lactobacillus, Leuconostoc</i>, and <i>Oenococcus</i> spp. Antimicrobial activity of pediocin PD-1 remained constant (1600 AU/mL) for 28 days in dry-fermented (yeast fermented) grape must adjusted to pH 3 and 4, respectively. However, antimicrobial activity decreased to 800 and 600 AU/mL after 48 hr in the same must when adjusted to pH 6 and 7, respectively. A complete loss in antimicrobial activity was recorded after 48 hr of incubation in grape must with a pH of 8 or 9. No change in antimicrobial activity was detected when pediocin PD-1 was incubated in must containing 15% (v/v) ethanol, 100 mg/L SO₂, or a combination thereof. When <i>Oenococcus oeni</i> was cultured in Chardonnay must (pH 3.8) and must supplemented with yeast extract (pH 3.8) the viable cell numbers of <i>O. oeni</i> decreased from 1 x 10⁶ cfu/mL to less than 10 CFU/mL after 4 days of incubation in the presence of 30 AU/mL pediocin PD-1. Pediocin PD-1 did not inhibit the growth of a commercial starter culture strain of <i>Saccharomyces cerevisiae</i> or a mutant with an impaired cell wall structure caused by deletion of the <i>CWP2</i> gene (Δ<i>cwp2</i>). Based on results, pediocin PD-1 effectively inhibited the growth of <i>O. oeni</i> and may provide an alternative to chemical preservatives.