After isolating clean algae, keep the algae under suitable conditions to prolong the time of transplanting while preserving the superiority in yield and quality that the algae line is available. Specifically, the method of isolating and keeping spirulina from a population of spirulina contaminated with foreign algae, bacteria and zooplankton, includes the following steps:
Step 1: Prepare selective nutrient medium including: sterile liquid medium, agar medium in petri dishes and inclined agar medium; was carried out in a sterile culture chamber and the agar layer thickness in the petri dish was in the range of 0.5-0.6 cm.
Step 2: Cumulative culture in a selective environment at temperatures ranging from 32-35°C, light intensity in the range of 5000-8000hix for 1 week.
Step 3: Isolation of algae by phototropic method: Isolation of algae on agar to separate pure algae, exclude foreign algae, bacteria and zooplankton, this step is carried out as follows: Filter algae from populations obtained in step 2 by filter cloth; smear the obtained filtrate into a dark streak with a diameter between 0.6-0.8cm in the center of the agar plate; cover and cover with clean sterile paper; cut a hole with a diameter of about l,5-2cm on the side of the paper at the bottom opposite the algae stain; keep the plates in the dark for 1 day and night at a temperature between 25-28 °C; then, put out the lights with a temperature between 28-30°C, the light intensity is in the range of 5000-8000 lux for a period of 5-7 days. To separate and propagate pure algae, this step is carried out as follows: use a sterile knife to cut a circle around the agar plate; Turn the plate upside down so that the agar drops onto the sterile paper; cut a thin top layer of agar containing clean spirulina cells and drop into a 100 ml conical flask containing the liquid medium prepared in step 1; leave the flasks in the dark overnight at a temperature between 25-30°C; then, put these bottles out to the lights with the temperature in the range of 25-28°C, the light intensity in the range of 1000-2000 lux; When the algae grows green, check the cleanliness of the algae again with a microscope to determine the right algae variety.
Step 4: Keep the algae on slanted agar at a temperature between 4-5.5°C, low light intensity in the range of 400-600 lux, poor in bicarbonate.