
A commercial way to extract more juice (and something we did in Biology lessons) is to add "pectolytic enzyme" to the apple pulp. This degrades the cell wall pectin and should impove juice yield by up to 20%. Also known as pectin destroying enzyme, pectinase etc etc.
the yeast found naturally on the apple skins is "saccharomyces pombe" which as a natural yeast hasn't been selectively bred to produce high alcohol contents but obv does the job. I should imagine cider is the first alcoholic drink man ever made.
Matt