Characterization of Lactobacillus carbohydrate fermentation activity usingimmobilized cell technique

A microbial bioreactor based on calcium alginate immobilized Lactobacillus cells coupled to a pH electrode was developed for quantitative determinatio n of carbohydrate fermentation activity. A high biomass (10(10) cfu mL(-1)) and particular pregrowth conditions were needed. Reduction of catabolite r epression by monosaccharides was achieved by pregrowth in lactose. The evol ution of acid production in a continuous flow-stopped flow bioreactor was m onitored for different sugar solutions in contact with the immobilized bact eria. The resulting slopes (Delta mV/Delta t) were used to quantify the fer mentation capability for a defined sugar related to that of glucose, which was taken as 100%. The procedure is simple, being based on pH variation tha t can give quantitative results compared to other reported techniques for c arbohydrate fermentation pattern from which only qualitative results are ob tained. In addition, it offers reduction in time and costs and is a suitabl e tool for the rapid analysis of isolated strains and in studies of modific ations of sugar metabolism in mutants.