title: Optimization of a Bifidobacterium longum production process.
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 2(8-4) 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 degrees C, yeast extract concentration 35 gl(-1) and glucose concentration 20 gl(-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 degrees C, a 10 h temperature gradient from 0 to +10 degrees C and a 12 h temperature hold at +10 degrees 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%.
authors.affiliation: Helsinki University of Technology, Laboratory of Bioprocess Engineering, P.O. Box 6100, FIN-02015 HUT, Finland. kristiina.kiviharju@hut.fi
authors.forename: Kristiina
authors.initials: K
authors.lastname: Kiviharju
authors.forename: Matti
authors.initials: M
authors.lastname: Leisola
authors.forename: Tero
authors.initials: T
authors.lastname: Eerikäinen
mesh_terms: D001644:Bifidobacterium / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology*; D001709:Biotechnology / Q000379:methods*; D018929:Cell Culture Techniques; D003470:Culture Media / Q000737:chemistry; D003545:Cysteine / Q000378:metabolism; D003890:Desiccation; D005285:Fermentation; D005612:Freeze Drying; D005947:Glucose / Q000032:analysis; D019936:Probiotics / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
chemical_list: D003470:Culture Media; D005947:Glucose; D003545:Cysteine