Sensitive lactate determination based on acclimated mixed bacteria and palygorskite co-modified oxygen electrode.

A sensitive bacteria biosensor was prepared for the detection of trace lactate. The sensitive bioelement, Lactobacillus bulgaricus and Streptococcus thermophilus mixed culture, and palygorskite, a perfect matrix for bacteria, was co-immobilized on the surface of oxygen electrode. The biosensor possesses fine selective specificity, good sensitivity and longer operational life time, which were due to the mutual help relationship of symbiotic bacteria and 240 days acclimation with lactate as the carbon source. Hydrodynamic amperometry, an advanced electrochemical method, is suitable for on-line monitoring the concentration change of dissolved oxygen that is closely accompanied with the metabolism of lactate. Electrochemical data show that the current is very sensitive to the changes of the concentration of lactate. The response current was linear with lactic acid concentration in the range from 0 to 300μmol L(-1), where the response time is no more than 240 s (R=0.9952), and the sensitivity was 1.87mA mol(-1)L. Experiments show the biosensor is also very useful for long time on-line monitoring of lactate, such as fermentation progress.