Ex. 16: Carbohydrate Fermentation Objectives??

Fermentation Tubes Contain Peptones and NaCl COH of interest (0.5 – 1%) Phenol red indicator (  alternate name “phenol red broth or PR broth”) Use to differentiate Enterobacteriaceae among themselves and from other Gram-neg. rods.

Materials needed per table:  Glucose fermentation tubes (3 or 4)  Lactose fermentation tubes (3 or 4)  Sucrose fermentation tubes (3 or 4) Three pure cultures needed per table:  Enterobacter aerogenes  Pseudomonas aeruginosa  Proteus vulgaris  (E. coli) Work as a table team. Each student will inoculate one of the organisms into all 3 different fermentation tubes. (If only 3 students per table: Leave out E. coli.) Day 1.

Table 16-1: Possible Results for Carbohydrate Fermentation Tests ResultInterpretationSymbol Yellow broth, bubble in Durham tube Fermentation with acid and gas as end products A/G Yellow broth, no bubble in Durham tube Fermentation with acid end products; no gas produced A/  Red or pink broth, no bubble in Durham tube No fermentation; more or less degradation of peptones with varying quantities of alkaline end products  /  K if pH 

Possible Reactions

Glucose Fermentation with Durham Tube

Lactose Fermentation

Sucrose Fermentation

Results for Fermentation Broth Tubes Organism Carbohydrate GlucoseLactoseSucrose GrowthAcidGasRead asGrowthAcidRead asGrowthAcidRead as E. aerogenes P. aeruginosa P. vulgaris