Immobilization of lactobacillus salivarius atcc 11741 on agricultural residues for lactic acid fermentation

Abstract

Cell immobilization method can maintain high cell concentration; enhanced fermentation productivity and cell stability. Reusing agricultural residues can minimize the environmental problems associated with their build-up reducing the use of noble materials. Hence, immobilization of Lactobacillus salivarius on agricultural residues is a challenging alternative. Agricultural residues used in this study were loofa sponge, sugarcane bagasse, tamarind fruit fibre, and coconut fibre. In the preparation step, large portion of water was needed in order to clean the tamarind fruit fiber thoroughly. In addition, this process was labour-and-time consuming. Therefore, it was not applicable for the industrial scale. After that L. salivarius ATCC 11741 was immobilized on untreated fibres. Cells could well adhere on loofa sponge and sugarcane bagasse but not on coconut fibre. As a result, agricultural residues that would be selected for further study were loofa sponge and sugarcane bagasse. In order to increase the surface area of the fibre for cell immobilization, H2O2 and chitosan were introduced as a surface modified reagent. Four molecular weights of chitosan used in this research were 83,000 Da, 185,000 Da, 380,000 Da, and 800,000 Da with the 90 – 92% DD. All experiments were conducted in shaking flask mode at 100 rpm shaking speed and 37C. At 1% w/v chitosan in 2% v/v acetic acid, it was found that product yield and productivity of various molecular weights chitosan were insignificant different. In repeated batch mode, immobilization using loofa sponge was found to exhibit a little higher lactic acid concentration, productivity, and number of repeated batch than sugarcane bagasse. The highest values for cell immobilized on loofa sponge and sugarcane bagasse were 0.56 and 0.53 in product yield, 0.94 and 0.80 g/L.h in productivity, and 5 and 3 in reusability, respectively.