To begin with, it is necessary to establish the patterns of bacterial growth (dX/dt) and the rate of absorption of the substrate (dS/dt). Determine the substrate constants (Ks) and substrate inhibition constants (Ki). Given that organic acid is produced (dP/dt), at some stage of the process it begins to inhibit the culture, it is necessary to determine inhibition by the product(Kp). Well, after that you can think about the speed of the substrate.

Dear Mr. Lakshmanan, It is not clear for me if you have already determined the substrate concentration that produced inhibition of cells growth. If you have this value, you should try to set the feeding rate/batch so as not exceed this inhibition concentration. You need to know the following parameters: digester volume, V [m3]; mass of substrate fed per batch, m [kg]; maximum concentration of organic matter that do not produce cell growth inhibition, max.c [%]. You may determine the maximum organic load per batch, OL [kg/m3 *batch], that means the organic matter to be fed into the digester per volume and batch: OL [kg/m3 *batch] = m [kg/batch] * max.c [%] / V [m3].

Hi Alagappan,

In systems for production of organic acids using anaerobic fermentation the end products i.e., the organic acids act as the self-inhibitors of the system. So try be very sure about if the inhibition in your system is actually expressed by the substrate or by the products. If you have already encountered substrate inhibition in your system, then you should try to reduce the concentration of the substrate from its current value, may be you can directly use half of it.

You can check the following book on fed-batch systems for reference:

Fed-Batch Cultures Principles and Applications of Semi-Batch Bioreactors by Henry C. Lim and Hwa Sung Shin. ISBN: 9780521513364

Also the book by M. L. Schuler and F. Kargi on Bioprocess Engineering Principles is a nice option to understand the basics in easy way.

Good luck,

Shiladitya