The following is a common method for the preparation of 1 liter of LB [source]:
Measure out the following:
- 10 g tryptone
- 5 g yeast extract
- 10 g NaCl
Suspend the solids in ~800 ml of distilled or deionized water.
Add further distilled or deionized water, in a measuring cylinder to ensure accuracy, to make a total of 1 litre.
Autoclave at 121 °C.
After cooling, swirl the flask to ensure mixing, and the LB is ready for use.
Adjusting the pH This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2009)
Prior to autoclaving, some labs adjust the pH of LB to 7.5 or 8 with sodium hydroxide. However sodium hydroxide does not provide any buffering capacity to the media, and this results in rapid changes to the pH during bacteria cultivation. As a result, some labs adjust the pH of LB with 5–10 mmol/L TRIS buffer, diluted from 1 mol/L TRIS stock.
High density bacteria cultures require more buffering capacity than 5-10 mM TRIS can provide.