Considerable interests and widespread studies in the development of
biodegradation of plastic materials have been carried out in order to overcome the
environmental problems associated with petrochemical plastics waste. Among the
various biodegradable polymers, poly(3-hydroxybutyrate) (PHB) is an attractive
substitute for conventional petrochemical plastics due to similar properties to
thermoplastics and elastomers, and complete biodegradability upon disposal under
various environments. PHB is the most famous member of polyhydroxyalkanoates
(PHAs) and can be accumulated as an intracellular carbon/energy source for various
microorganisms. Synthesis of these distinct granules occurs when there is a growth
limiting component in the presence of excess carbon source. The use of PHB in a wide
range of applications has been hampered mainly by their high production cost
compared with petrochemical based polymers. The fermentation performance, carbon substrate, the isolation of new microorganisms with high growth rate and potential of
production as well as yield and recovery method affect the production cost of PHB. To
overcome mentioned problems, knowing the specific strategies such as controlled
systems is necessary. In controlled cultivation- and production systems like bioreactors,
high cell density occurred. Hydrodynamic and mass transfer behaviors are important in
gas liquid bioreactors. Oxygen transfer and residence time distribution must be
monitored on-line. The mixing characteristics of gas liquid bioreactors are often
intermediates between the characteristics of plug-flow and well mixed flow. This
phenomenon is modeled using two methods: the axial dispersion model and tanks-in
series model. In this chapter after a glance introducing of PHB and producing bacteria
which grow on different carbon sources in batch, fed-batch, and continuous systems
have been reviewed and compared to each other from the productivity point of view.
Also, a special interest has been done on inhibition kinetics as well as modelling of gas
and mass transfer in different bioreactors.
Keywords: Axial dispersion model, Bioreactor cascade, Bioreactors, Fed-batch
cultivation, Fermentation, Forced-liquid bioreactors, Hydrodynamics, Mass
transfer behavior, On-line monitoring, Polyhydroxyalkanoates (PHA), Poly(3-
hydroxybutyrate) (PHB), Process design, Tanks in a series model.
