The Influence of Biomass Preparation on Physiological Activity of Bacterium Lactobacillus plantarum Strain L4 During Storage at Different Freezing Temperatures

Vjera Runjić-Perić, Sanja Poljak, Vedranka Bobić, Rajka Božanić, Ivanka Pavušek

Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 41000 Zagreb, Croatia;
*INA-Oil Industry, Research and Development, Savska c. 41, 41000 Zagreb, Croatia

Article history:
Received October 3, 1994
Accepted December 22, 1994

Summary:
Today the lactic acid bacteria (LAB) are routinely used as starter cultures in fermented food production; species Lactobacillus plantarum is used mostly for vegetables and olives conservation, ensiling and malolaclic fermentation of wines. In this work the influence of Lb. plantarum L4 biomass preparation for longterm preservation by freezing at different temperatures on physiological activity (i.e., viability and metabolic activity) was investigated. After growth in optimal conditions the bacterial biomass was prepared for freezing in the following ways: a) biomass sediment obtained after centrifugation was resus-pended in the whole volume of neutralized spent growth medium (BNNM); b) biomass sediment was resuspended in 1/5 th of spent growth medium volume (CB), and c) after centrifugation the bacterial biomass was rinsed and then resuspended in the physiological saline until reaching cell concentration as in a) MB). During 100 days of storage at -20, -30 and -70 °C the viability of cells by plate count method and metabolic activity via lactic acid production were followed. At all investigated freezing temperatures through the storage period the survival of Lb. plantarum 1.4 in BNNM was complete. Meanwhile, in washed biomass (WB) the survival of cells was considerably poorer, i.e., after 100 days of storage at -20, -70 and -30 "C there was only 42, 48 and 5% of living cells, respectively. The survival of Lb. plantarum L4 in CB at investigated temperatures was among 71 and 81 %. In all experimental conditions at the end of storage period the metabolic activity of frozen/ /thawed cells expressed as lactic acid production ratio of these cells and nonfrozen control was between 86 and 90 %.