Produção de probióticos com Lactobacillus imobilizados em alginato de cálcio empregando soro de queijo

Abstract

The purpose of the present study is to explore the use of cheese whey fermentation for the production of probiotic from super concentrated cultures of Lactobacillus acidophilus entrapped within dried calcium alginate gel beads and placed inside a nutritive solid medium which constitute an animal feed. The two steps before the animal feed production (fermentation and immobilization) were evaluated. Preliminary experiments in 50mL penicillin flasks reactor and 250 mL erlenmeyer reactors were realized in a rotary shaker at 100 rpm and a temperature of 28  3oC. The best time for these experiments were 36h for the fermentation in 250 mL erlenmeyer reactor and 48h for the fermentation in 50 mL penicillin flasks reactor. The fermentation of cheese whey from powder cheese whey and in natura cheese whey were optimized through response surface methodology (central composite design) for concentration of lactose, pH, and inoculum size. The experiments in 250 mL reactor resulted in optimized variables: lactose concentration of 27-35 g/L, inoculum concentration of 0.8-1.2 g/L anp pH 6 -7. The experiments in 50 mL reactor resulted in optimized variables: lactose concentration of 30-38 g/L, inoculum concentration of 1.0-1.4 g/L anp pH 6 -7. In addition, the kinetics of reaction in optimized conditions (33 g/L of lactose, pH 6.5, and 1.0 g/L of inoculum) in 250mL erlenmeyer reactor and 1800 mL batch stired tank reactor were evaluated. It was found the concentration of viables cells of 1010 MPN/mL in 1800 mL reactor and a close kinetic behavior, in relation to cellular growth, in 250 mL reactor shown the agreement of the results obtained by 250 mL fermentation and by 1800 mL fermentation. The dried calcium alginate immobilized cells presented 1.93.1011 MPN/g of cells. Stability studies in acid conditions indicated that the immobilized cell at pH 2.5 presented D value of 62.5 min which allows these cells to survive from stomach fluid. The thermal stability study shows that the immobilized cells presented an activation energy of cell death of 73.76 kJ/mol. In respect to the study of animal feed preparation, the combined evaluation of nutrients, temperature, number of cells and drying time demonstrated that the preparation with immobilized cells have reached quality standards necessary for their designated category.