I think it very much depends on which bacteria you are working with, but I would be surprised if you could get a very slow growing strain to double as fast as E. coli.  Worth experimenting with different medias and temperatures etc anyway.

1. Medium - ingredients, something to eat...

2. Aeration

Thanks #Rory Little, for answering. I don't think it is possible to turn a slow grower as fast as E. coli. I used example of E. coli as a context to understand time required for fast growing bacteria compare to slow growing bacteria.

BTW i am working with some slow growing Azotobacter those have excellent effect on plant growth promotion. But the problem is during inoculum preparation while others bacterial growth reach at a sufficient stage by 36-48 hours and these strains takes almost  120-168 hours to reach that sufficient level. In this case it would be  very helpful if there is a way to reduce 120 hours to 48 hours or less.

The simple answer is: no.

You can speed up growth a little bit by optimising culture conditions (broth, ingredients, temperature, O2 content, pH), but this will change things not dramatically.

Good luck.

agreed, if you have optimal growth medium then you are not likely to speed up growth. However it is possible that your growth conditions are not optimal or that you are missing some key nutrient in your medium that is causing slow growth. 

The simple answer is: no

You can optimize environmental conditions (pH, temperature, CO2 atmosphere, broth ingredients), but this will change things not dramatically. Good luck

Thanks Professor Benedik & Professor Solbach for your kind information. As I am using an optimized medium (Jensen agar medium) so there may be no plausible chance to get a dramatic results. Now I can try optimizing the environmental conditions. Thank you again for your valuable opinion.

Lower temperature

Maybe you can also consider to modify the media with minor dose of antibiotics or heavy metals (less than MIC), considering a common tradeoff between microbial multiplication and resistance .

I agree with Feng Ju. 

Despite possessing a nascent to near nonexistent prior ethos in this discussion...I think you have an excellent problem worth exploring, though it will be difficult to solve.

If you choose to only work with this bacterium in an isolated culture, I do not believe you will have success in this investigation unless you try to promote a greater rate of mutation within your culture line.  Adding small amounts of growth inhibiting agents may help you identify more rapidly growing cell lines within the culture. Continually subculture the more rapid growing colonies with varying inhibitory factors over time and possibly, if you are persistent for long enough, you could succeed in inducing a stable modified strain of the species.  Screening for such a mutant could be done without induction by an inhibitory factor as well by selecting the first colonies visibly present on optimal or minimal growth media for subculture, and repeating this process indefinitely in the hopes of promoting the genetic mutation. 

In addition to being tedious and having a low probability of success, this could prove to be a difficult process as you are working with a cyst-producing genus designed to stop vegetative growth in poor environmental conditions.  It is possible that you would have to continually work through both phases to permanently alter the original DNA content.  I would imagine that inducing such a mutation to a cell line within your culture would only be possible by forcing each selected suspect mutant colony from vegetative to cyst-phase cells, then germinating this line in a variety of media with different limiting/promoting growth factors, followed by selecting the fastest growing colonies from these trials to subculture once more for induced cyst formation, rinse and repeat.  Experiment with the amount of time incubated in subculture and/or chemostasis before inducing cyst formation to explore any differences in the conservation of genetic mutations during lag, log, and stationary phases. 

This genus is reported to contain plasmids as well, so that could be another long shot option if you can identify an appropriate gene, vector, and induction process. 

While you might get lucky attempting to induce a suitable mutant strain, this may take more time than you have to devote to the effort.  While I myself would still pursue this path to appease and express my ego, I would simultaneously explore the microbial community from which your bacterium was sourced.  I would try growing the culture with various bacteria and fungi known to co-exist in their ecological niche and hope one or more of these species produce a growth factor beneficial to your bacterium.  This is the most logical direction of investigation in my opinion, and the rest of what I have proposed was mostly for the sake of promoting a theoretical discussion in early diagnostic microbiology.

Good Luck