SCOBY

SCOBY is an acronym for Symbiotic Culture Of Bacteria and Yeast. It refers to the living microbial community—and the cellulose matrix that houses it—used to ferment sweetened tea into kombucha (black or green tea base) or jun (green tea with honey). The bacterial component consists predominantly of acetic acid bacteria, chiefly Acetobacter xylinum (now reclassified as Komagataeibacter xylinus), which produce the structural cellulose pellicle and convert ethanol to acetic acid (vinegar). The yeast component—comprising species of Brettanomyces, Zygosaccharomyces, and others depending on origin—hydrolyzes sucrose and ferments glucose and fructose to ethanol and CO₂. These organisms operate in a mutualistic relationship: yeasts produce ethanol that bacteria can metabolize; bacteria acidify the environment, discouraging competing organisms that yeasts cannot tolerate alone. A mature SCOBY floats at or near the surface of the fermentation vessel as a rubbery, tan-to-brown disc; it grows thicker with each brew cycle and will produce a new 'baby' layer with each batch. The SCOBY is maintained by perpetuating it with liquid starter (prior kombucha at low pH) and fresh sweetened tea. Temperature range for active fermentation is 24–30°C (75–86°F); below 18°C the culture becomes dormant. The SCOBY can be stored in a 'hotel' jar (acidified tea) in the refrigerator for months. Cultures are highly regional and variable—their microbial composition shifts with local environment, tea type, and handling history—making every SCOBY a unique living system.

“She peeled the baby SCOBY away from the mother disc and slid it into a fresh hotel jar with a cup of starter liquid to pass on to a neighbor.”

• ConceptPellicle (Fermentation)
• TechniqueKombucha Brewing
• ConceptLacto-Fermentation

1. 1.The Noma Guide to Fermentation — René Redzepi & David Zilber (Artisan, 2018)
2. 2.Kombucha!: The Amazing Probiotic Tea That Heals — Hannah Crum & Alex LaGory (Avery, 2016)
3. 3.Wild Fermentation — Sandor Ellix Katz (Chelsea Green, 2nd ed., 2016)
4. 4.Microbiological and Biochemical Aspects of Kombucha Fermentation — Rasu Jayabalan et al., Comprehensive Reviews in Food Science and Food Safety (2014)

Confidence: high