Feruloyl Esterase Protocols

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These are methods to screen for and assay Ferulic-acid Esterase activity.

Plate Screen


  • Ethyl ferulate solution (100mg/ml in dimethylformamide).
  • Agar plates of media appropriate to your microorganism.
    • If screening natural strains some find it helpful to eliminate glucose from the media to drive FAE secretion.
    • This means that you will have to make this media yourself and can't buy a premix.
  • Water
  • Agar or Agarose (agarose is preferred)


1. Grow colonies on agar plates of appropriate media until colonies reach a decent size.
2. For each plate to be screened, add 25-30mg agar to 6ml of water (i.e. if your screening 3 plates thats 80mg agar to 18ml water).
3. Microwave the agar mix until the agar is melted and put in 60°C water bath.
4. Once the media has been in the water bath for 10 mins:

1. Add the 20μL of ethyl ferulate solution for every ml of top agar (120μL per plate), and swirl lightly to disperse.
  • You want the ethyl ferulate to look cloudy in the agar so don't swirl too hard.
  • Bubbles = Enemy
2. Pour onto grown colonies immediately.

5. Incubate for ~4 hours.
6. If a clear halo forms around the colony in the top agar then it's positive for FAE!!!


  • Donaghy et al. (1998) added the ethyl ferulate solution directly to the media plates at a final concentration of 2mg/mL while Hassan and Pattat (2011) added it to the top agar at a stated concentration of 0.05mg/ml. We've found that the hassan and pattat concentration is way too low to make the agar cloudy but 1mg/ml can work well in a pinch. -- Mike
  • Agarose instead of agar is better too for top agar.

Nitrophenyl Ferulic Acid Assay


  • Protein desalting columns
  • sodium azide
  • Dnase
  • 4-nitrophenyl ferulic acid


  1. Make Protein buffer
    1. 100mM hepes
    2. 10μg/mL sodium Azide
    3. 5μL/mL Dnase
  2. Concentrate cellular proteins from 1mL culture into 100μL buffer
  3. Make Substrate buffer
    1. 2.5mM 4-nitrophenyl ferulic acid
    2. 0.5MKPO4
  4. Add 20μL protein to 80μL substrate
  5. Incubate for 30 mins at 37°C


Hydrolase Assay

This is a general assay which uses pH as a metric of ester hydrolysis. The colormetric assay is based on the pH indicator 4-nitrophenol. It is very important to get the pH correct on the initial buffers.


Donaghy, J., P. F. Kelly, et al. (1998). "Detection of ferulic acid esterase production by Bacillus spp. and lactobacilli." Applied Microbiology and Biotechnology 50(2): 257-260.

Mastihuba, V., L. Kremnicky, et al. (2002). "A spectrophotometric assay for feruloyl esterases." Analytical Biochemistry 309(1): 96-101.

Nsereko, V. L., B. K. Smiley, et al. (2008). "Influence of inoculating forage with lactic acid bacterial strains that produce ferulate esterase on ensilage and ruminal degradation of fiber." Animal Feed Science and Technology 145(1-4): 122-135.

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