Culture Vessels
Culture vessels should have the following properties: non-toxic (chemically inert); reasonably transparent to light; easily cleaned and sterilized; and provide a large surface to volume ratio (depending on the organism).
Certain materials which could potentially be used for culture vessels may leach chemicals which have a deleterious effect on algal growth into the medium. The use of chemically inert materials is particularly important when culturing oceanic plankton and during isolation. Recommended materials for culture vessels and media preparation include Teflon, polycarbonate, polystyrene, and borosilicate glass.
Culture vessels are usually borosilicate glass conical flasks (narrow or wide mouth Erlenmeyer flasks) of various volumes (from tens of milliliters to 3–5 l) or test-tubes for liquid culture, and testtubes for agar cultures.
Borosilicate glass flasks and tubes, which have been shown to inhibit growth of some species, can be replaced by more expensive transparent polycarbonate vessels, which offer excellent clarity and good physical strength. Like borosilicate, polycarbonate is autoclavable, but is expensive and becomes cloudy and cracks with repeated autoclaving, undergoing some loss of mechanical strength. Teflon is very expensive and it is used only for media preparation, and polystyrene, the cheaper alternative to Teflon and polycarbonate, is not autoclavable. Polystyrene tissue culture flasks can be purchased as single-use sterile units (Iwaki, Nunc, Corning) and used for transport purposes.
The vessels are capped by non-adsorbent cotton-wool plugs, which will allow gas transfer but prevent entry of microbial contaminants. A more efficient and costly way of capping is to use foam plugs or silicone bubble stoppers (bungs), which also allow efficient gas transfer: they are re-usable and autoclavable. Glass, polypropylene, or metal covers and caps are also used for flasks and tubes.
Materials which should generally be avoided during microalgal culturing include all types of rubber and PVC.
