Could you please give more information about your process?

PB is usually used for screening a large number of variables affecting a proposed process, and could be the first step in the optimization process but definitely you will need a more sophisticated algorithm to attain the full optimum conditions!

Do you need procedure for performing PBD analysis

OR

Variables to choose in this experiment?

Hi Sakshi, first you need screen the levels of significant factors, maybe using a fractional factorial design. Then, establish a PBD with those significant factors to optimize biomass production.

Key factors could be:

C/N ratio, phosphate, agitation, pH, temperature, and some microelements like Mg, Mn which are important for lactobacillus.

Standard practice with statistical design experiments is to start with a screening design like PB design or factorial design. PB designs are normally used when there are a lot of factors to screen and as Amhed says are a good first step. If you have a smaller number of factors factorial design can be used. Once these screening designs are complete you use the significant factors from the screening experiments to create an optimisation experiment typicaly using a central composite design.

A number of point to consider before diving into the experiment

Use "Blocking" to remove effects of uncontrolled factors (eg multiple inocula)  

Make sure that you understand the variability in experiment ouptut response

Make sure that you can make up the different growth media accuractly and consistantly.

I would strongly recommend doing a dry run of replicate center and corner points before diving into to experiment so as to understand variability and get your protocols working.