Fig. 1.1 Fig. 1.1 shows an industrial fermenter used to produce the antibiotic penicillin from the fungus Penicillium. The fungus is grown in a large stainl...

This question tests how an industrial fermenter is controlled to grow Penicillium and produce penicillin at high yield. Every control feature exists to keep conditions at the optimum for the fungus and to keep the culture pure.

(a) The microorganism used to produce penicillin is a fungus / Penicillium [1].

(b) The water jacket's purpose is to remove heat / cool the fermenter and keep the temperature constant [1].

(c) Temperature must be controlled because the reactions release heat [1]; too high a temperature denatures enzymes / kills the microorganism [1]; too low a temperature slows growth, so an optimum is maintained for the best yield [1]. Both extremes reduce output, so a steady optimum is best.

(d) The stirrer paddles mix the contents / keep the microorganisms in contact with the nutrients [1]; and spread temperature and oxygen evenly through the vessel [1].

(e) Sterile air is bubbled in because the microorganism needs oxygen for (aerobic) respiration [1]; and being sterile it prevents contamination by other microbes [1].

(f) The fermenter is sterilised beforehand to kill any unwanted microorganisms that would compete with the fungus or contaminate the product [1].

(g) pH is monitored because a pH probe measures it continuously [1]; pH is kept at the optimum for the enzymes / microorganism [1]; since the wrong pH would slow growth or reduce the yield [1].

Exam tip: for fermenter questions, tie every feature to one of two goals - keeping conditions at the optimum for growth, or keeping the culture free of contamination. That framing answers most parts.