Coffee cherry
Coffee cherry

The Microbiology of Coffee
Christine L. Case, Ed.D.
Biology Professor
Skyline College




Coffea flower
Coffee flower

Microbial fermentation is used to process the seeds of Coffea. The skin (exocarp) and pulp (outer mesocarp) are removed from the coffee cherry mechanically. The two beans are then put in a fermentation tank to degrade the hygroscopic inner mesocarp. Lactic acid bacteria initiate acidification of the coffee mass and solubilization of pectin. The highly methylated pectin is degraded by endogenous coffee enzymes.

Look at the graph below. What causes the pH to decrease?

Aerobic bacteria

Klebisella spp

Lactic acid bacteria

Leuconostoc mesenteroides
Lactobacillus brevis


Cryptococcus laurentii, C. albidus
Kloeckera apis
Candida gulliermondii

Pectinolytic bacteria

Klebsiella pneumonia
Erwinia herbicola

: .

Reference: S. Avallone et al. "Microbiological and Biochemical Study of Coffee Fermentation." Current Microbiology 42:252-256, 2001.