French to English Tech/Engineering Engineering (general) biogas production in a landfill

This is taken from a very long document about landfill management - biogas production in particular. I am having trouble with the phrase above - although the rest of the paragraph is clear to me - and, I hope, self-explanatory for the purposes of this question. I show my effort below the French and would be most grateful for comments/suggestions. The phrase appears towards the end of the paragraph.

La production du biogaz

Lors de la biodégradation de la matière organique des déchets stockés en ISD, du biogaz est produit selon différentes phases [23]. D’abord il y a l’hydrolyse réalisées par des bactéries hydrolytiques, étape au cours de laquelle les macromolécules qui constituent la matière organique se décomposent en petites molécules solubles en présence d’eau et ***à l’origine du jus de fermentation. ***Contrairement aux phases suivantes, cette phase est aérobie.

And here's what I have so far:

During biodegradation of the organic matter in the waste stored in a landfill, biogas is produced depending on the various phases.[23]. Firstly there is hydrolysis caused by hydrolytic bacteria, a stage during which the macromolecules which constitute the organic matter break down into small soluble molecules in the presence of water and ***et à l’origine du jus de fermentation. ***Unlike the following phases, this phase is aerobic.

I am understanding the 'jus de fermentation' to be the 'fermentation liquids' which cause the waste mass to ferment and thus produce biogas...

Does it simply mean something like: in the presence of water and thus the formation of fermentation liquids? Or am I missing something here? I am sure someone out there will know the answer!