What is the procedure for using Red Starch (S-RSTAR) on agar pates to detect microbial colonies that are known to produce alpha-amylase? What should positive results look like?

Modified on Thu, 23 Sep, 2021 at 4:00 PM

In plate tests, you should see a cleaning zone where microbial cultures grow.  The Red Starch is depolymerised by alpha-amylase and will diffuse throughout the plate giving a zone of lighter colour.  A concentration of 0.1% is correct.  You may try even lower.  Ensure that the pH of the Agar is in line with enzyme requirements, i.e. pH 4.5-5.5 for fungal and 6.0-7.0 for bacterial alpha-amylases.


Product Page (S-RSTAR)

Was this article helpful?

That’s Great!

Thank you for your feedback

Sorry! We couldn't be helpful

Thank you for your feedback

Let us know how can we improve this article!

Select at least one of the reasons
CAPTCHA verification is required.

Feedback sent

We appreciate your effort and will try to fix the article