# Steam sterilization of whey in a bioreactor

I'm trying to design a bioreactor to produce citric acid with whey and Aspergillus Niger.

The first step in the process would be to put whey into the reactor with some dextrose (approx. 10%). Then, this solution should be sterilized, and I was thinking of using batch steam sterilization by direct injection of the steam in the reactor. The sterilization should be done at 121°C.

I'm not sure how to calculate the sterilization time and the amount of steam required for a given reactor volume (approx. 600 m3). I was thinking of calculating it as if I had a 600 m3 autoclave, but I doubt the approximation holds. In that case, the death kinetics would be given by the Arrhenius equation:

$$k = Ae^{\frac{-E}{RT}}$$

I'd need to determine the activation energy, $E$, the pre-exponential factor $A$, or some approximation for $k$. Then, I'd just have to integrate the equations for the heat and hold energy required:

\begin{align} \nabla heat &= ln(\frac{N_0 V_0}{N_1 V_1}) = \int_{t_0}^{t_1} k(t) dt \\ \nabla hold &= ln(\frac{N_1 V_1}{N_2 V_2}) = k(t2_-t_1) dt \end{align}

To figure out $t_1$ and $t_2$.

Am I approaching this problem correctly?

• Do you know the SAL you need? My process engineering handbook goes into this, but only briefly and I want to think about it a bit before I give a wrong answer. – mart May 3 '15 at 20:14
• Sterilization can be achieved both with temperature and pressure. Maybe you should investigate the pressure side of the question as well. – BOB Feb 11 '16 at 19:09