title: Development of a new method, based on a bioreactor coupled with an L-lactate biosensor, toward the determination of a nonspecific inhibition of L-lactic acid production during milk fermentation.
abstract: The development and characteristics of a bioreactor employing bacteria (Streptococcus thermophilus) encapsulated in Ca-alginate beads coupled with an L-lactate biosensor are reported. The biosensor comprises a carbon paste electrode modified with enzymes HRP (horseradish peroxidase), LOD (lactate oxidase), and FcH (ferrocene) as redox mediator. The measurement of L-lactate is based on the signal produced by H(2)O(2), the product of the enzymatic oxidation of L-lactate by LOD. The detection of H(2)O(2) is performed at the electrode surface via HRP/FcH at low operating potential (-100mV vs Ag/AgCl). Optimization studies were performed using the bioreactor in conjunction with an L-lactate electrode operating in a flow injection system to assess the ability of encapsulated bacteria to ferment carbohydrate solutions. The possibility of using the developed method to assess the fermentation capability of milk samples was evaluated. Bronopol (2-bromo-2-nitro propane-1,3-diol) was chosen to simulate the effect of an inhibitory agent of milk fermentation. The obtained results indicated that the evaluation of the amount of L-lactate amount produced through the bioreactor could be used as a measure of inhibition of lactic acid production in milk samples.
authors.affiliation: Groupe Electrochimie, Laboratoire d'Analyse Isotopique et Electrochimique de Métabolismes, UMR-CNRS 6006, Faculté des Sciences et des Techniques, 2, rue de la Houssinière, B.P. 92208, 44322 Nantes Cedex 03, France.
authors.forename: Rola
authors.initials: R
authors.lastname: Zaydan
authors.forename: Michel
authors.initials: M
authors.lastname: Dion
authors.forename: Mohammed
authors.initials: M
authors.lastname: Boujtita
mesh_terms: D000464:Alginates; D000818:Animals; D019149:Bioreactors; D015374:Biosensing Techniques / Q000379:methods*; D004566:Electrodes; D005285:Fermentation; D017022:Flow Injection Analysis; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D019344:Lactic Acid / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D008892:Milk / Q000737:chemistry*; D006899:Mixed Function Oxygenases; D013291:Streptococcus
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D019344:Lactic Acid; D020723:Glucuronic Acid; D006899:Mixed Function Oxygenases; C021497:lactate 2-monooxygenase