Ginger beer plant is a symbiotic yeast & bacteria culture that can be used to make all sorts of soft drinks (not just ginger ale) the old-fashioned way. Here is how to make such a culture.
Put a tablespoon of the diced ginger and 1/2 oz brewers yeast into a mason jar 3/4 full of water.
Add 2 teaspoons white sugar.
Leave the jar in an exposed place (not in your refrigerator).
Every day for a week, add 2 teaspoons of sugar and 2 teaspoons of diced ginger.
Check the mixture. It should be bubbly with a pleasant odor. If it is moldy, dump it and start over at step 1.