title: The use of a D-optimal design to model the effects of temperature, NaCl, type and acid concentration on Lactobacillus pentosus IGLAC01.
abstract: OBJECTIVE
  To study the effects of temperature, NaCl and acid (HCl, citric, acetic and lactic) concentrations on the specific growth rate (mu), lag phase (lambda), and h0 of Lactobacillus pentosus IGLAC01.
  
  
  RESULTS
  Response surface (RS) methodology (D-optimal design) was used with a dummy variable, to account for the different types of acids. The variable ranges were: 16-30 degrees C, 0-70 g l-1 NaCl, and 0-5 g l-1 acid (or 0-2.5 g l-1 HCl). Time to detection from optical density data was used to deduce mu and lambda. The RS models for log2mu and log2lambda, according to acid types, were estimated and the effects of variables were quantified by their z-generalized values. A relationship between ln h0 with temperature was also found.
  
  
  CONCLUSIONS
  The mu of L. pentosus IGLAC01 can be doubled by increasing temperature by 10.3 degrees C or by decreasing NaCl by 48 g l-1 (harmonic, averaged, z values, Z); citric was the least inhibitory acid (zmu=-96.2) and lactic the strongest (zmu=-5.7), according to their generalized z values, z. A twofold lambda increase was achieved from a decrease of 3.1 degrees C (HCl), or 4.27 degrees C (citric) or 36 g l-1 NaCl increase (both acids) (expressed as zlambda ); the same effect was obtained from a decrease of 4.37 degrees C, 54 g l-1 NaCl increase, or 10 g l-1 acetic or lactic acid additions (expressed as Zlambda values).
  
  
  CONCLUSIONS
  Valuable information on the effects of environmental variables on the biological parameters of L. pentosus IGLAC01, which could be used for the optimization of olive, cucumber or other vegetable fermentations, is obtained.
authors.affiliation: Food Biotechnology Department, Instituto de la Grasa (CSIC), Seville, Spain.
authors.forename: F N A
authors.initials: FN
authors.lastname: López
authors.forename: M C D
authors.initials: MC
authors.lastname: Quintana
authors.forename: A G
authors.initials: AG
authors.lastname: Fernández
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D019343:Citric Acid / Q000378:metabolism; D005285:Fermentation; D005516:Food Microbiology; D005519:Food Preservation; D006851:Hydrochloric Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism; D007778:Lactobacillus / Q000378:metabolism*; D050296:Microbial Viability; D008954:Models, Biological; D015233:Models, Statistical; D031658:Olea; D012965:Sodium Chloride; D013696:Temperature
chemical_list: D019343:Citric Acid; D019344:Lactic Acid; D012965:Sodium Chloride; D019342:Acetic Acid; D006851:Hydrochloric Acid