Well, this depends much on the conditions you start with, what we compare with, and also which yeast you have. If you for instance currently use a synthtetic medium e.g YNB, you can always make the yeast happier by adding yeast extract. If you get dense culture and come to a respiratory phase, commonly oxygen will be limiting, so better shaking or oxygenation will speed up growth. If you use a synthtic medium with ammonium as nitrogen source you may soon be limited by too low pH, meaning that a suitable buffer will increase growth rate. The possibilities are almost endless, I just mentioned a few. Good luck!

thanks for your response. I am working with s.cerevisiae and using YPD media.normally a noticeable yeast growth is observed after 12-16 hrs, i want to reduce this duration to as low as possible (say 3-4 hrs)

Then work on your preculture. There is no reason that you should have a long lag phase, or any lag at all, provided that you have a young growing preculture in same medium. A population growing in YPD, in the first respirofermentative phase, that is before glucose finnished, and not too small inoculum and you will see growth directly.

YPD is quite a nutritionally rich medium, it is great for growing S. cerevisiae as well as any other species. However, in order to make your yeasts grow faster I tend to agree with Thomas, try working on your preculture. Also, you can try try to start your culture with a larger inoculum.

I am not sure whether it will work with S.cerevisiae since I've never tried growing that species in that way, but I believe it should play its part - namely you can add some glucose to the medium.

YPD is usually best rich media. That said, growth rate can decrease if certain amino acids are not present at optimal levels. Tryptophan can be sensitive to autoclaving, for instance, and you may need to supplement your media. Strains with auxotrophies may grow slightly faster and reach a more dense stationary phase when supplemented with amino acids. Supplement ade- strains with adenine for instance. Lag phase can be limited by outgrowth and using log-phase cells for the inoculum, but there is no way you will get faster than the 90 minutes or so optimal doubling rate of lab strains. That number is tied to the evolutionary history of S. cerevisiae and cannot be easily reduced by environment. 

Sunita Mehta I have the same question. Did you find a way to expedite the growth rate of yeast? would you mind sharing it?

Thank you