Method for preparation of algal cells, and kit for evaluation of toxicity of chemical substance

1. A kit for evaluating a toxicity of a chemical substance by delayed luminescence, the kit including a biologically pure strain of cultured algal population and an effective amount of a frost damage protectant,

wherein said population consists essentially of cultured algal cells frozen in a logarithmic growth phase at −80° C. or less,

wherein the algal cells are Pseudokirchneriella subcapitata,

wherein the algal population exhibits a bimodal particle size distribution curve, and

wherein the algal population is brought to a temperature of −80° C. or less in response to human intervention at a point during logarithmic growth phase such that:

when the algal cells are strain No. NIES-35 in National Institute for Environmental Studies, at least 55% of the total number of the frozen algal cells have a particle size not smaller than that at a valley value in the bimodal particle size distribution curve, or

when the algal cells are strain ATCC No. 22662 in the American Type Culture Collection, at least 46% of the total number of the frozen algal cells have a particle size not smaller than that at a valley value in the bimodal particle size distribution curve; and

wherein the kit maintains the frozen algal population at a temperature of −80° C. or less until the algal population is to be thawed in order for a user of the kit to perform the evaluating of the toxicity of a chemical substance.

2. A kit according to claim 1 , wherein at least 50% of the total number of the algal cells have a particle size of 4.5 μm or greater.

3. A kit according to claim 1 , wherein the algal cells are green algae ( Pseudokirchneriella subcapitata ) preserved as strain No. NIES-35 in National Institute for Environmental Studies; and

wherein the number of cells at the larger-particle-size peak in the bimodal particle size distribution curve is at least 50% of the total of the number of cells at the smaller-particle-size peak and the number of the cells at the larger-particle-size peak.

4. A kit according to claim 1 , wherein the algal cells are green algae ( Pseudokirchneriella subcapitata ) preserved as ATCC No. 22662 in the American Type Culture Collection; and

wherein the number of cells at the larger-particle-size peak in the bimodal particle size distribution curve is at least 37% of the total of the number of cells at the smaller-particle-size peak and the number of the cells at the larger-particle-size peak.

5. A kit according to claim 1 , wherein the algal cells are prepared by a method comprising the steps of:

cultivating the algal cells in the logarithmic growth phase in a culture solution;

centrifuging the culture solution containing the algal cells;

completely removing from the algal cells a culture supernatant separated by the centrifuging; and

freezing the remaining algal cells at −80° C. or less.