"Anaerobic fermentation" is a process where microorganisms break down sugar or carbohydrates into different substances in the absence of oxygen. Full definition
This smell is produced by the bacterial consumption of fiber and as a product of anaerobic fermentation (including in the colon and as body odor). (drstevenlin.com)
(For more on aerobic and anaerobic fermentation see Water Kefir: Oxygen or No Oxygen.) (it-takes-time.com)
Along with talking about the protocol of GAPS, we also cover anaerobic fermentation and probiotics, with a bonus workbook and a handy PDF probiotics guide included. (bodywisdomnutrition.com)