Cp. Champagne et al., INCREASING THE STABILITY OF IMMOBILIZED LACTOCOCCUS-LACTIS CULTURES STORED AT 4-DEGREES-C, Journal of industrial microbiology, 13(6), 1994, pp. 367-371
Immobilized cell technology was used to prepare concentrated cultures
of Lactococcus lactis that lost only 22% of viability over a 30-day st
orage period at 4-degrees-C. Concentrated cultures of L. lactis CRA-1
were immobilized in calcium alginate beads and added to glycerol, NaCl
or sucrose-NaCl solutions in order to obtain a(w) readings ranging fr
om 0.91 to 0.97. The suspensions were subsequently placed at 4-degrees
-C and viability (CFU g-1 of bead) was followed during storage. Viabil
ity losses were high at a(w) readings of 0.95 and 0.97, and pH dropped
significantly (up to one unit) in the unbuffered solutions. Addition
of 1% soytone or glycerophosphate helped stabilize pH, and a beneficia
l effect on viability during storage was observed in the glycerol-soyt
one mix when the beads were added to the conservation solutions immedi
ately following immobilization. When beads were added to the conservat
ion solutions immediately following immobilization, a 70% drop in cell
counts occurred during the first 5 days of incubation. Dipping the L.
lactis-carrying beads in milk for 2 h before mixing with the glycerol
-soytone 0.93 a(w) solution reduced this initial 5-day viability loss.
Cultures grown in the alginate beads also had good stability in the 0
.93 a(w) glycerol-soytone solution, where 78% of the population was vi
able after 30 days at 4-degrees-C. The process could be used to store
immobilized cells at a processing plant, or by suppliers of lactic sta
rters who wish to ship cultures without freezing or drying.