Abstract:

This study was designed to examine the effect of different lyophilization protectants based on skim milk
and storage conditions (－20, 4 ℃ or room temperature, 16－25 ℃, and different periods of time) on the relative
luminous efficiency of lyophilized cells of V. qinghaiensis sp.-Q67 and P. phosphoreum sp.-T3. The results showed that
P. phosphoreum sp.-T3 had better tolerance than V. qinghaiensis sp.-Q67 during the freeze-drying process. After 30 min of
recovery, the lyophilized cells of both strains with a mixture of kim milk, sucrose and chitosan as the protectant showed the
highest luminous efficiency. The best temperature was －20 ℃ for long-term storage of V. qinghaiensis sp.-Q67 lyophilized
with a protectant composed of skim milk, sucrose, chitosan and sodium glutamate. P. phosphoreum sp.-T3 lyophilized with
any one of the three protectants investigated had good stability during long-term storage irrespective of －20, 4 ℃ or room
temperature. Both lyophilized strains could react within 30 min, indicating their potential application in rapid toxicity tests.

Key words: V. qinghaiensis sp.-Q67, P. phosphoreum sp.-T3, protectant optimization, lyophilization, storage stabilty