title: Effects of acetic acid and arginine on pH elevation and growth of Bacillus licheniformis in an acidified cucumber juice medium.
abstract: Bacillus licheniformis has been shown to cause pH elevation in tomato products having an initial pH below 4.6 and metabiotic effects that can lead to the growth of pathogenic bacteria. Because of this, the organism poses a potential risk to acidified vegetable products; however, little is known about the growth and metabolism of this organism in these products. To clarify the mechanisms of pH change and growth of B. licheniformis in vegetable broth under acidic conditions, a cucumber juice medium representative of a noninhibitory vegetable broth was used to monitor changes in pH, cell growth, and catabolism of sugars and amino acids. For initial pH values between pH 4.1 to 6.0, pH changes resulted from both fermentation of sugar (lowering pH) and ammonia production (raising pH). An initial pH elevation occurred, with starting pH values of pH 4.1 to 4.9 under both aerobic and anaerobic conditions, and was apparently mediated by the arginine deiminase reaction of B. licheniformis. This initial pH elevation was prevented if 5 mM or greater acetic acid was present in the brine at the same pH. In laboratory media, under favorable conditions for growth, data indicated that growth of the organism was inhibited at pH 4.6 with protonated acetic acid concentrations of 10 to 20 mM, corresponding to 25 to 50 mM total acetic acid; however, growth inhibition required greater than 300 mM citric acid (10-fold excess of the amount in processed tomato products) products under similar conditions. The data indicate that growth and pH increase by B. licheniformis may be inhibited by the acetic acid present in most commercial acidified vegetable products but not by the citric acid in many tomato products.
authors.affiliation: College of Food Science and Engineering, Yangzhou University, Yangzhou, Jiangsu 225001, People's Republic of China; Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695-7624, USA.
authors.forename: Zhenquan
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695-7624, USA.
authors.forename: Xia
authors.initials: X
authors.lastname: Meng
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, South East Area Food Science Research Unit, North Carolina State University, Raleigh, North Carolina 27695-7624, USA. Fred.Breidt@ars.usda.gov.
authors.forename: Frederick
authors.initials: F
authors.lastname: Breidt
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, South East Area Market Quality and Handling Research Unit, North Carolina State University, Raleigh, North Carolina 27695-7624, USA.
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Dean
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695-7624, USA.
authors.forename: Fletcher M
authors.initials: FM
authors.lastname: Arritt
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology*; D001120:Arginine / Q000494:pharmacology*; D001407:Bacillus / Q000187:drug effects* / Q000254:growth & development; D019343:Citric Acid / Q000494:pharmacology; D015169:Colony Count, Microbial; D018553:Cucumis sativus / Q000382:microbiology*; D005285:Fermentation; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D000067030:Fruit and Vegetable Juices / Q000382:microbiology*; D006863:Hydrogen-Ion Concentration; D012492:Salts / Q000737:chemistry
chemical_list: D012492:Salts; C017082:brine; D019343:Citric Acid; D001120:Arginine; D019342:Acetic Acid