Nutrient requirements for acetone-butanol-ethanol production from whey permeate by Clostridium acetobutylicum P262 in a range of bioreactors : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University, Palmerston North, New Zealand
The acetone-butanol-ethanol (ABE) fermentation process, using Clostridium
acetobutylicum P262, was studied. Experiments were conducted in a traditional
batch fermentation using freely-suspended cells in a defined medium with
lactose as carbon source. Solvent production did occur under conditions of
nitrogen-, phosphate- or iron-limitation. However, the optimum conditions were
observed when all nutrients were present slightly in excess of growth
requirements. A greater excess of nutrients caused the fermentation to be
acidogenic rather than solventogenic.
Sulphuric acid casein whey permeate, without nutrient supplementation, proved
to be a poor substrate for growth and solvent production by this organism.
However, the addition of yeast extract (5 g/1) led to strong solventogenesis. The
deficiency in the whey permeate was shown to be iron rather than assimilable
nitrogen, phosphate or vitamins.
Experiments were also performed in a defined medium in continuous culture
using freely-suspended cells in a CSTR. An inverse relationship was observed
between the biomass concentration and the specific butanol productivity. It is
suggested that this was due to the cell population not being homogeneous, and
that a change in the nutrient balance led to a change in the relative proportions
of acidogenic, solventogenic and inert cells (spores).
The addition of supplementary yeast extract during continuous solvent
production from whey permeate using free cells in a CSTR showed that yeast
extract supplementation of less than 1 g/1 favoured acid production rather than
solvent production. It is unlikely that high solvent productivities can
be attained with this substrate in a single stage continuous culture system with
freely-suspended cells. A maximum solvent productivity of 0.05 g/l.h was
observed in continuous culture compared to 0.06 g/l.h in batch culture.
A continuous fermentation process was investigated using cells immobilized by
adsorption onto bonechar and operated in a packed bed reactor. Three nutrients
(i.e. nitrogen, phosphate and iron) were selected for this investigation. Solvent
production was favoured by high concentrations of these nutrients in the
influent medium. It was not possible to restrict the supply of phosphate or iron
in the reactor due to leaching of the bonechar. However, conditions where
biomass growth was restricted by a restriction in the nitrogen supply were not
conducive to solvent production.
This reactor was also operated using whey permeate as the substrate. The
biomass build-up was controlled by minimizing the supplementary yeast extract
concentration of the feed, but this had deleterious effects on solvent production.
Hence, when producing solvent from whey permeate in this type of reactor a
compromise must be made between strong solventogenesis and reactor
Content removed due to copyright restriction:
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Kanchanatawee, S. S., & Madox, I. S. (1990). The nutritional status of whey permeate as a substrate for the abe fermentation. In P-L, Yu (ed.),Fermentation Technologies: Industrial Applications (pp. 173-177). London, UK: Elsevier Applied Science.
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