A steam steriliser is used to sterilise liquid medium for fermentation. The initial concentration of contaminating organisms is 108 per litre. For design purposes, the final acceptable level of contamination is usually taken to be 10-3cells; this corresponds to a risk that one batch in a thousand will remain contaminated even after the sterilisation process is complete. For how long should 1 m3 medium be treated if the temperature is 140⁰C ________________. To be safe, assume that the contaminants present are spores of Bacillus stearothermophilus, one of the most heat-resistant microorganisms known. For these spores the activation energy for thermal death is 283 kJ gmo1-1 and the Arrhenius constant is 1036.2 s-1 -triyambak.org