Growth and Arginine Metabolism of the Wine Lactic Acid BacteriaLactobacillus buchneriandOenococcus oeniat Different pH Values and Arginine Concentrations

Abstract

During malolactic fermentation (MLF) in grape must and wine, heterofermentative lactic acid bacteria may degrade arginine, leading to the formation of ammonia and citrulline, among other substances. This is of concern because ammonia increases the pH and thus the risk of growth by spoilage bacteria, and citrulline is a precursor to the formation of carcinogenic ethyl carbamate (EC). Arginine metabolism and growth of Lactobacillus buchneri CUC-3 and Oenococcus oeni strains MCW and Lo111 in wine were investigated. In contrast to L. buchneri CUC-3, both oenococci required a higher minimum pH for arginine degradation, and arginine utilization was delayed relative to the degradation of malic acid, the main aim of MLF. This allows the control of pH increase and citrulline formation from arginine metabolism by carrying out MLF with pure oenococcal cultures and inhibiting cell metabolism after malic acid depletion. MLF by arginine-degrading lactobacilli should be discouraged because arginine degradation may lead to the enhanced formation of acids from sugar degradation. A linear relationship was found between arginine degradation and citrulline excretion rates. From this data, strain-specific arginine-to-citrulline conversion ratios were calculated that ranged between 2.2 and 3.9% (wt/wt), and these ratios can be used to estimate the contribution of citrulline to the EC precursor pool from a given amount of initial arginine. Increasing arginine concentrations led to higher rates of growth of L. buchneri CUC-3 but did not increase the growth yield of either oenococcus. These results suggest the use of non-arginine-degrading oenococci for inducing MLF.The term MLF refers to the microbial conversion of L-malic acid to L-lactic acid in grape musts or wine by MLB. MLB are wine LAB belonging to three genera and include homo-and heterofermentative lactobacilli, homofermentative pediococci, and the heterofermentative species Oenococcus oeni (formerly Leuconostoc oenos) (15). MLF may be due to MLB naturally present in wine, but nowadays MLF is often induced with commercial starter cultures. Its main effects are to reduce the acidity of wines by converting dicarboxylic malic acid to monocarboxylic lactic acid and the modification of flavor properties (8). O. oeni is the preferred species for carrying out MLF, whereas most lactobacilli and pediococci are considered undesirable or spoilage bacteria because of flavor depreciation (6).Besides malic acid, some heterofermentative MLB degrade arginine, which is quantitatively one of the most important amino acids in grape musts and wines (25,27). Complete degradation of arginine by MLB occurs via the ADI pathway, leading to the production of ammonia, ornithine, ATP, and CO 2 (14). During the degradation of arginine, some citrulline is excreted (13). Arginine degradation by MLB has several enological implications (Fig. 1): the production of ammonia increases the pH and the risk of growth of spoilage microorganisms; formation of ATP may give arginine-positive MLB, including spoilage MLB, ...

Arginine metabolism in wineLactobacillus plantarum: in vitro activities of the enzymes arginine deiminase (ADI) and ornithine transcarbamilase (OTCase)

“…Ethyl carbamate (or urethane), a well known animal carcinogen (Zimmerli and Schlatter, 1991) found in many fermented foods, including wine (Canas et al, 1994, Kodama et al, 1994, may be produced from precursors such as urea which is produced by yeasts, while citrulline and carbamyl phosphate are produced by LAB through the arginine deiminase (ADI) pathway (Liu and Pilone, 1998;Mira de Orduña et al, 2000Liu, 2002;Spano et al, 2002). However, a positive effect of arginine on growth of wine lactic acid bacteria has been observed by several authors suggesting that arginine may facilitate growth of LAB in wine (Tonon and Lonvaud-Funel, 2000;Mira de Orduña et al, 2001). Moreover, arginine degradation in wine LAB may also play a role in adaptation to low pH (Lonvaud-Funel, 1999;Tonon and Lonvaud-Funel, 2000;Mira de Orduña et al, 2001;Cotter and Hill, 2003;Spano et al, 2004).…”

“…However, a positive effect of arginine on growth of wine lactic acid bacteria has been observed by several authors suggesting that arginine may facilitate growth of LAB in wine (Tonon and Lonvaud-Funel, 2000;Mira de Orduña et al, 2001). Moreover, arginine degradation in wine LAB may also play a role in adaptation to low pH (Lonvaud-Funel, 1999;Tonon and Lonvaud-Funel, 2000;Mira de Orduña et al, 2001;Cotter and Hill, 2003;Spano et al, 2004).…”

“…Although the ADI pathway consists of three enzyme activities (ADI, OTCase, CK), due to the carbamylphosphate instability (Mira de Orduña et al, 2001;Arena et al, 2002;Arena and Manca de Nadra, 2005), only two (ADI and OTCase) were analysed in order to test the ability of wine L. plantarum to degrade arginine. The activity of enzymes ADI and OTCase was detected in all the strains analysed.…”

“…However, high concentrations of arginine reduce growth of wine L. plantarum as already reported for O. oeni and Lactococcus lactis subsp. lactis strains (Mira de Orduña et al, 2001) and competition with other amino acids by a common amino acid carrier has been proposed as inhibitory mechanism (Mira de Orduña et al, 2001).…”

Genomic analysis ofOenococcus oeniPSU-1 and its relevance to winemaking

“…Some oenococcal strains convert arginine, one of the most abundant amino acids in musts and wines, to ornithine, ammonia and CO 2 via the arginine deiminase pathway [48,49]. This pathway provides a means for direct synthesis of ATP and has been shown to enhance cell growth and survival [50].…”