Understanding Fermentation Behaviour Of Lactic Acid Bacteria Grown On Resistant Starch As The Substrate

Resistant starch (RS) is bracketed along with dietary fibre components and its importance as a prebiotic food is increasingly recognized all over the world. However, its mode of fermentation by large intestinal lactic acid bacteria is not understood in detail with respect to its degradation by the induced amylolytic enzymes during its fermentation. Hence in the present study, seven Lactic acid Bacterial Cultures were evaluated for their ability to degrade RS. The major amylolytic enzymes i.e amylases/debranching enzyme activities were negligible in the culture filtrates. However, a membrane bound alpha-glucosidase was detected in significant amounts of all the seven culture filtrates of Lactic acid bacteria among which Lactobacillus fermentum culture filtrates showed maximum activity. Hence, conditions were optimized by employing response surface method using Box-Behnken Design with RS as the sole substrate in order to obtain an enhanced alpha-glucosidase activity from Lactobacillus fermentum. The optimized conditions for L. fermentum NCDC156 to produce maximum alpha-glucosidase activity (U/ml) were 6% (v/w) inoculum, 18 hours of fermentation at 30 +/- 1 degrees C. The optimized conditions resulted in more than two fold increase in alpha-glucosidase concentration as compared with the control. The use of detergents in the extraction media enhanced alpha-gluesidase activity substantially, indicating the membrane bound nature of the enzyme.