Optimization of a Bifidobacterium longum production process

Optimization of a Bifidobacterium longum production process
21 February 2005
Kristiina Kiviharju, Matti Leisola and Tero Eerik?inen
Journal of Biotechnology
Science Direct
Abstract
Bifidobacteria are used as probiotics mainly in the dairy industry as cell suspensions or as freeze-dried additives. So far there have been no reports on a thorough investigation on factors influencing the production process or a statistical approach to the optimization thereof. A 28-4 fractional factorial design was used in determining the critical parameters influencing bioreactor cultivations of Bifidobacterium longum ATCC 15707. Glucose, yeast extract and l-cysteine concentrations were found critical for the cultivation of this strain. Glucose and yeast extract concentrations were further studied together with temperature in a three factor central composite design. The optimized cultivation conditions were temperature 40 ?C, yeast extract concentration 35 g l-1 and glucose concentration 20 g l-1. Freeze-drying of frozen cell suspensions of B. longum was studied first in controlled temperatures and thereafter with temperature programming experiments. The results were statistically evaluated. A temperature program with a 2 h temperature gradient from -10 to 0 ?C, a 10 h temperature gradient from 0 to +10 ?C and a 12 h temperature hold at +10 ?C was found best for the freeze-drying process. Temperature programming reduced drying times by over 50% and improved the product activity by over 160%.