Production of polyb-hydroxy butyrate (PHB).van Aalst et al. (1997)studied the formation of PHB by…

Production of polyb-hydroxy butyrate (PHB).van Aalst et
al. (1997)studied the formation of PHB by the bacterium Paracoccus
pantotrophusin acontinuous, stirred tank reactor operated at steady state. When
growing under N-limitation but with an excess of the carbon source the organism
can build up a large carbon storage that can be used to support active growth
when, or if the N-limitationis lifted. This is part of the clean-up cycle in
waste water treatment plants, but PHB has an independent and increasing
interest as a biodegradeable polymer – incompetition with particularly
polylactides.

Production of polyb-hydroxy butyrate (PHB).van Aalst et
al. (1997)studied the formation of PHB by the bacterium Paracoccus
pantotrophusin acontinuous, stirred tank reactor operated at steady state. When
growing under N-limitation but with an excess of the carbon source the organism
can build up a large carbon storage that can be used to support active growth
when, or if the N-limitationis lifted. This is part of the clean-up cycle in
waste water treatment plants, but PHB has an independent and increasing
interest as a biodegradeable polymer – incompetition with particularly
polylactides. Although PHB is a part of the biomassit can just as well be
regarded as a metabolic product. Its formula is

P = CH1.5 O0.5 per carbon atom. The
remainder of the biomass (the “active” biomass) has

The formula X = CH1.73O0.44N0.24
per carbon atom. The organism uses acetic acid,CH3COOH as
carbon and energy source. It grows aerobically, and some CO2isproduced together
with X and P.

(a) The result of two experiments, one with N-limitation
and one with C-limitationare given below

For each of the two experiments determine the yield
coefficients in the black box model

(b) For each of the two experiments calculate the exit
concentrations of X and P when there is no X or P in the feed. Also calculate
the inlet concentrations of acetic acid and ammonia.

(c) Could any single kinetic expression describe the
results of both experiments?