Very similar to this question I would like to know how to best make my Ginger Beer Plant grow. Another but related question would be what the most important factors for growth are. Water? Temperature? Sugar? Citric acid? I would like to not add lots of stuff that would not usually be part of Ginger Beer.
To grow Saccharomyces and Lactobacillus you need three things:
- Energy - This comes from sugars and oxygen
- Fat - This can be, to some extent, synthesized from carbohydrates (sugar) and oxygen
- Protein - This cannot be created using water, sugar, and citric acid. These things simply does not contain enough nitrogen, not to mention that only specific nitrogen carriers are really accessible to your plant.
As you can see, one of three things is simply missing. Minuscule amount of protein present in ginger root will at best allow your plant to retain it's volume, but it's far from enough to increase it. You need some source of easily accessible amino acids in your nourishment fluid. And no recipe for ginger beer I ever seen included anything like it.
Beer wort is great for that because malt is designed by nature to provide everything needed for growth. Ginger root, on the other hand, was designed by nature as energy source mostly - it can regrow whole plant, but only when actively gathering nitrogen from the ground (oversimplifying, of course). And sugar is exactly nothing but energy source by design. OK, it can be made into fat, but that's only because fat is long-term energy storage by nature's* design.
TL;DR You can't, unless you would use pretty non-standard things anyway.
* I don't care if it was nature. Or if it was anything like design. No philosophy intended.