82 CHAPTER 4
Fig. 4.17Diagram of the air-lift fer-
menter used by Marlow Foods for the
production of mycoprotein in continuous
flow culture. (From Trinci 1992.)novel food product, termed Quorn mycoprotein. In fact,
this is the sole survivor of the much-heralded “single-
cell protein” revolution of the late 1900s, when
scientists and international aid agencies attempted to
develop protein-rich foods from microbial biomass, to
meet the impending protein shortage in the develop-
ing world.
The development of Quorn is a major technological
success, which took over 20 years to reach fruition. Now
Quorn products are available in many supermarkets
and are widely used as alternatives to meat products
because of their nutritional profile (see Table 1.2).
Quorn mycoprotein is produced commercially from
chemostat cultures of the fungus Fusarium venenatum,
which is grown at 30°C in a medium composed of glu-
cose (the carbon source), ammonium (the nitrogen
source), and other mineral salts. The fungal mycelium
is retrieved continuously from the culture outflow,
then aligned to retain the fibrous texture, and vacuum-
dried on a filter bed before being constituted into
meat-like chunks. In this case a continuous culture sys-
tem was deemed necessary in order to ensure a high
degree of reproducibility of the product, and also for
economic reasons because the yield of mycelium over
a period of time was about five times higher than if a
series of batch cultures were used. Glucose is used as
the growth-limiting nutrient in the production system,
and the dilution rate is set to give a doubling time (μ)
of 0.17–0.20 h−^1 , which is below the μmaxof 0.28 h−^1.
The rate of substrate conversion to protein is extremely
high, about 136 g protein being produced from every
1000 g sugar supplied. For comparison with this, the
equivalent production of protein by chickens, pigs, and
cattle would be about 49, 41, and 14 g respectively.
Trinci (1992) has described the many stages in
the development of this fermentation technology.