Amperometric Determination of l-Lactate Based on Entrapment of Lactate Oxidase on a Transducer Surface with a Semi-Permeable Membrane Using a SIRE Technology Based Biosensor. Application:  Tomato Paste and Baby Food

Abstract

Determination of dissolved L-lactate in tomato paste and baby food samples using a SIRE-based (sensors based on injection of the recognition element) biosensor is reported. The measuring principle is based on the use of a small amount of enzyme, which is injected into an internal delivery flow system and held in direct spatial contact with the amperometric transducer by the use of a semipermeable membrane. Measurements are based upon the reversible enzymatic conversion of L-lactate to pyruvate and hydrogen peroxide by lactate oxidase. Differential measurements are performed in which the samples are measured in the presence and absence of enzyme allowing for control over matrix interferences present in crude samples. The linear range investigated for the determination of L-lactate in tomato paste and baby food was 0-0.1 mM using a lactate oxidase concentration of 22 U/mL. Samples were diluted with buffer prior to biosensor measurements. The L-lactate concentrations of the tomato paste and baby food were determined to be 1.02 +/- 0.02 mM and 2.51 +/- 0.10 mM, respectively, using the standard addition method. The repeatability for tomato paste and baby food measurements was 2.5% (RSD, n = 15) and 4.0% (RSD, n = 15) and the reproducibility was 13.0% (RSD, n = 45) and 3.0% (RSD, n = 45), respectively. The concentration of dissolved L-lactate can be used as a measure of freshness in the food industry. All biosensor measurements were compared with measurements from an established spectrophotometric assay (Boehringer Mannheim). It was found that the biosensor had good correlation with the spectrophotometric method. The biosensor gave 12% higher values for the tomato paste measurements and 2.5% higher values for the baby food measurements. However, a distinct advantage of the biosensor is that it can perform L-lactate measurements within 3 minutes, whereas the spectrophotometric assay requires a 35-minute measurement time.

An L‐Lactate Amperometric Enzyme Electrode Based on L‐Lactate Oxidase Immobilized in a Laponite Gel on a Glassy Carbon Electrode. Application to Dairy Products and Red Wine

“…In other work, LOx, together with Glucose oxidase and Galactose oxidase was immobilized in polypyrrole and poly(ethylene glycol) [26]. It has also been described in literature the use of semipermeable membranes to keep the enzyme close to the electrode surface [27]. The immobilization of LOx together with Lactate dehydrogenase and Horseradish peroxidase on an oxygen selective Clark electrode with a Teflon membrane, working either in batch or in a flow injection mode was also reported [28].…”

Facilitating electron transfer in bioelectrocatalytic systems

“…27 In the food industry, L-lactate determination is used for control of fermentation and for quality control of several products such as tomato sauces, fruits, juices, milk and wine. 28,29 In order to achieve low detection times at low costs, L-lactate oxidase from Pediococcus species has been used by many laboratories in the construction of lactate oxidase-based bioelectrocatalytic systems. 30 The enzyme has the advantage of high specificity over other enzymes used for lactate determination.…”

Novel reagentless electrodes for biosensing

“…34 In the food industry, the l-lactate level is an indicator of fermentation and is related to the quality of several products such as tomato sauces, fruits, juices, milk, and wine. 35,36 The structure of the active site of lactate oxidase is not well known yet, as it always has different number of cofactors and water molecules in the structure and it is difficult to stabilize the holoenzyme biomolecule. It is known that the active site contains flavin mononucleotide (FMN).…”