PichiaPink™ Media Kit

This is likely due to low inoculum. We recommend having a starter culture to use, as it is more accurate than using a colony. You can use the doubling time to calculate the starting OD. In YPD, the doubling time is about 1.5 hours. In MGY, the doubling time is going to be about 3 hours.

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Generally, large colonies represent transformants containing pPIC6/pPIC6α integrants, while small colonies represent transformants containing pPIC6/pPIC6α non-integrants. These non-integrants have transduced the pPIC6/pPIC6α plasmid, and therefore, exhibit a low level of blasticidin resistance in the initial selection process. Upon subsequent screening, these non-integrant transformants do not retain blasticidin resistance.

When choosing a blasticidin-resistant transformant for your expression studies, we recommend that you pick blasticidin-resistant colonies from the initial transformation plate and streak them on a second YPD plate containing the appropriate concentration of blasticidin. Select transformants that remain blasticidin-resistant for further studies.

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Here are some suggestinos:

- Make sure that you have harvested cells during log-phase growth (OD <1.0 generally).
- If electroporation is being used, see the electroporator manual for suggested conditions. Vary electroporation parameters if necessary.
- Use more DNA.
- Use freshly made competent cells.
- If the LiCl transformation method is being used, try boiling the carrier DNA.

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Here are some things to consider:

- If the OD of cells that are used is too high, they will not spheroplast. Do not overgrow cells.
- Do not use old cells and make sure that they are in log phase of growth.
- Make sure to mix zymolyase well before using. Zymolyase is more of a suspension than a solution.
- Make the PEG solution fresh each time and check the pH.

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Bacto-Tryptone and Bacto-Peptone are two different and specific types of peptones. Bacto-Tryptone is a slightly poorer nitrogen source, and more of the nitrogen is provided by tyrosine and tryptophan. When comparing the two as components of media for Pichia growth, growth curves may differ slightly, but there should be only minor differences between the two. In Pichia media formulations that include Yeast Nitrogen Base as a primary source of nitrogen, such as BMGY and BMMY, there should be very little or no difference.

Find additional tips, troubleshooting help, and resources within our Protein Expression Support Center.