Fermentation: Enzymes, Substrates and SCFA

By: Chloe McClanahan, Biofiles Edition 6.2

The influence of probiotics on the metabolic activity of intestinal microbiota may be evaulated by detecting bacterial enzymatic activity in fecal samples, specifically β-glucosidase, β-glucuronidase, and urease activity. Experimental studies using probiotics have indicated a significant decrease in β-glucuronidase activity. A decrease in β-glucuronidase decreases the release of carcinogens from carcinogen-glucuronide conjugates within the colonic lumen.

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Name Specific Activity Unit Definition Form Cat. No.
from almonds

from almonds
≥2 units/mg solid

10–30 units/mg solid
One unit will liberate 1.0 μmole of glucose from salicin per min at pH 5.0 at 37 °C. lyophilized powder

lyophilized powder

from Escherichia
≥20,000 units/mg protein

1,000,000–5,000,000 units/g protein

5,000,000–20,000,000 units/g protein

20,000,000–60,000,000 units/g protein

units/g protein

≥10,000,000 units/g protein
One Sigma or modified Fishman unit will liberate 1.0 μg of phenolphthalein from phenolphthalein glucuronide per hr at 37 °C at pH 6.8 (30 min assay). lyophilized powder

lyophilized powder

lyophilized powder

aqueous glycerol solution

lyophilized powder

lyophilized powder





Urease from Canavalia ensiformis (Jack bean) 15,000–50,000 units/g solid

50,000–100,000 units/g solid

≥600,000 units/g solid

One micromolar unit will liberate 1.0 μmole of NH 3 from urea per min atpH 7.0 at 25 °C. It is equivalent to 1.0 I.U. or 0.054 Sumner unit (1.0 mg ammonia nitrogen in 5 minutes at pH 7.0 at 20 °C) powder



glycerol solution




Detection Substrates


Name Assay Cat. No.
3-Acetylumbelliferyl β-D-glucopyranoside ≥95% A3582
5-Bromo-4-chloro-3-indolyl β-D-glucopyranoside ≥97% B4527
6-Bromo-2-naphthyl β-D-glucopyranoside ≥99%, TLC B7877
6-Chloro-3-indolyl β-D-glucopyranoside ≥99.0%, HPLC 93546
Fluorescein di-(β-D-glucopyranoside) ≥90% F4521
Indoxyl β-D-glucoside ≥97% I3750
Indoxyl β-D-glucoside ≥97% I6893
2-Methoxy-4-(2-nitrovinyl)phenyl β-D-glucopyranoside ≥95% M2918
4-Methylumbelliferyl α- D -glucopyranoside M9766
4-Methylumbelliferyl β-D-glucopyranoside M3633
2-Nitrophenyl β-D-glucopyranoside N8016
4-Nitrophenyl α-D-glucopyranoside ≥99% N1377
4-Nitrophenyl β-D-glucopyranoside ≥98%, TLC N7006
Resorufin β-D-glucopyranoside ≥90% R4758


Name Assay Cat. No.
5-Bromo-4-chloro-3-indolyl β-D-glucuronide cyclohexylammonium salt ≥98% B3783
5-Bromo-4-chloro-3-indolyl β-D-glucuronide cyclohexylammonium salt ≥98%, TLC B6650
5-Bromo-4-chloro-3-indolyl β-D-glucuronide cyclohexylammonium salt 10 mg substrate per tablet
5-Bromo-4-chloro-3-indolyl β-D-glucuronide cyclohexylammonium salt ≥98% B0522
5-Bromo-4-chloro-3-indolyl β-D-glucuronide sodium salt ≥98% B5285
5-Bromo-4-chloro-3-indolyl β-D-glucuronide sodium salt 10 mg substrate per tablet B8174
5-Bromo-6-chloro-3-indolyl β-D-glucuronide cyclohexylammonium salt ≥98% B4532
6-Chloro-3-indolyl-β-D-glucuronide cyclohexylammonium salt ≥97.0%, HPLC 24907
Indoxyl β-D-glucuronide cyclohexylammonium salt I7638
4-Methylumbelliferyl β-D-glucuronide hydrate ≥98%, TLC M9130
Naphthol AS-BI β-D-glucuronide N1875
4-Nitrophenyl β-D-glucuronide ≥98%, TLC N1627
Phenolphthalein β-D-glucuronide P0501
Phenolphthalein β-D-glucuronide sodium salt P0376
4-Trifl uoromethylumbelliferyl glucuronide potassium salt ≥98%, TLC T6410

Short-Chain Fatty Acids (SCFA)

Probiotics and prebiotics enhance SCFA end product synthesis. An increase in SCFA production lowers the gastrointestinal pH thus improving pathogen resistance and stimulating epithelial cell proliferation. The predominant SCFA, butyrate, is the preferred substrate for colonocytes which likely contributes to a normal colonocyte population and a lower cancer risk. SCFA production can be measured with gas chromatography analysis on fecal samples or intestinal modeling systems. However, due to normal colon absorption of 95% of the SCFA metabolites, stable isotope technology is a superior method of analysis.

Non-Labeled Short-Chain Fatty Acids

Name Cat. No.
Acetic acid, ReagentPlus ®, ≥99% A6283
Butyric acid, ≥99% B103500
Hexanoic acid, 99% H12137
Isobutyric acid, 99% I1754
Isovaleric acid, 99% 129542
Propionic acid, reagent grade, ≥99% P1386
Valeric acid, ≥99% 240370

Isotec® Short-Chain Fatty Acid Isotopes

Name Cat. No.
Sodium acetate-1- 13 C, S & P tested, 99 atom % 13 C 668656
Sodium acetate-1- 13 C, 99 atom % 13 C 279293
Sodium butyrate-1- 13 C, 99 atom % 13 C 292656
Sodium propionate-1- 13 C, 99 atom % 13 C 279455


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