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52 P R A C T I C A L W I N E R Y & V I N E YA R D June 2015 W ine is a stressful environment for lactic acid bacteria (LAB), as acidity, alcohol, SO 2 and temperatures below 18° C are all factors that inhibit LAB growth. In addition, during alcoholic fermentation (AF) yeast may produce such growth- inhibiting factors as SO 2 , medium-chain fatty acids and certain peptides, deplet- ing the wine of available nutrients. Juice or wine clarification and other enological practices may eliminate nutrients and particulate matter, both of which are necessary to support the growth of wine LAB. Wine lactic acid bacteria are known to have complex nutritional needs for carbon, nitrogen, vitamins and minerals. When musts or wines are deficient in one or more of these components, a major impact on malolactic fermentation (MLF) may be observed. Nutrients Carbohydrates In wine, sugars are the primary source of energy for lactic acid bacteria and play an essential role in the growth of LAB. The main sugars found in must and wines are the hexoses, glucose and fructose. LAB are capable of utilizing both, although Oenococcus oeni prefers fructose. However, the co-metabolism of glucose and fructose is advantageous in terms of energy production. At the end of alcoholic fermentation, the glucose and fructose concentrations are low. Nevertheless, both hexoses are present in sufficient levels to meet the car- bon requirements of inoculated selected wine LAB. Most wine LAB are capable of utilizing the monosaccharides arabinose, mannose, galactose and xylose, etc., as well as polysaccharides and glycosylated compounds. 10.14,22 Glycosides represent a latent pool of aroma compounds, where the aglycone is conjugated to glucose and a second sugar molecule via glycosidic bonds that require either heat or enzymatic activity to release the active aroma compound. O. oeni and other wine LAB species pos- sess this glycosidase activity. 7,8,9,15,16 Wine LAB glycosidase action will cleave this bond, releasing aroma precursors and glucose, which may be used as a carbon source for further bacterial growth. Organic Acids L-malic acid The concentration of L-malic acid in grape must depends on grape maturity and varies from 0.7 to 8.6 g/L. 3 The main reaction of MLF is the decarboxylation of L-malic acid to L-lactic acid. This decarboxylation, in addition to increas- ing wine pH and decreasing acidity, allows to derive a small but measurable amount of energy in the form of adenos- ine triphosphate (ATP) and to maintain an intracellular pH favorable for enzyme activity and cell growth. Citric acid Citric acid is a component of must and wine that is present in a quantity between 0.1 and 0.7 g/L. Not only is the degradation of citric acid by wine *Magali Déléris-Bou, **Sibylle Krieger-Weber, Ph.D. and ***Goran Milanov, Ph.D. *Lallemand bacteria lab manager, Toulouse, France, **Lallemand bacteria R&D manager, Korntal-Münchingen, Germany, ***associate professor at Institut of Agriculture Skopje at University St. Cyril and Methodius Skopje, Macedonia BY Managing nutrition of wine bacteria to minimize the effect of inhibitors Part I 0 20 40 60 80 100 120 Control Ala Pro Giy Lys Thr Ile His Trp Leu Asp Met Arg Cys Val Tyr Glu Phe Ser Amino acid eliminated % ∆ OD from the control Lalvin 31 Figure 1. Twelve amino acids were essential for Lalvin 31 growth. 0 20 40 60 80 100 140 120 Control Ala Giy Thr Pro Lys Cys Iso Arg Val His Asp Leu Trp Met Ser Tyr Phe Glu Amino acid eliminated % ∆ OD from the control Enoferm Alpha Figure 2. Seven amino acids were essential for Enoferm Alpha growth. W I N E M A K I N G 57 When winemakers do everything correctly: Challenges of difficult-to-ferment juices By Linda F. Bisson, Vidhya Ramakrishnan, Lucy Joseph, Koichi Sakamoto, Peter Luong, Qinqwen Fan, Yan Luo and Gordon Walker 63 Where to install soil moisture sensors By Fritz Westover T E C H N I C A L R E S O U R C E F O R G R O W E R S & W I N E R I E S Don Neel, Editor practicalwinerylibrary.com Access Practical Winery & Vineyard article archives online.