Poly-B-hydroxybutyrate (PHB): A Biodegradable Polymer of Microbial Origin - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 51

table 3. (Continued)

Substrate Polyhydroxybutyrate (PHB)

Gram-Positive Reference Gram-Negative Reference

Industrial
Waste

Actinobacillus
Bacillus
Rhodococcus

Son et al., 2004
Vijayendra et al., 2007
Fuchtenbusch

Azotobacter
Burkholderia
Pseudomonas

Cho et al., 1997
Alias et al., 2005
Koller et al., 2008 and

Steinbuchel, 1999

Culture Systems
Mixed cultures or co-culture systems have been recognized to be important for several
fermentation processes. Several studies have claimed the integrity and effectiveness
of the system using mixed cultures. To date, considerable efforts have been carried out
about PHB production using mixed culture by many researchers, in general, the PHB
production of mixed cultures as summarized in following Table 4 by providing differ-
ent growth conditions.

table 4. PHB production under different growth conditions.

Conditions PHB

Production (%)

References

Aerobic 70.79 Sayyed and Gangurde, 2010

Semi aerobic 7.5 Sayyed and Gangurde, 2010

Micro aerophilic 62.0 Ueno et al., 1993

Feast-famine (aerobic) 62.0 Beccari et al., 1998

Feast-Famine Process 66.8 Dionisi et al., 2001

Fully aerobic 70.0 Punrattanasin, 2001

Feast-Famine Process 78.5 Serafim et al., 2004

Feast-Famine Process 37.9 M. Din et al., 2004

Under these growth conditions, the mixed culture subjected to consecutive periods
of external substrate accessibility ( feast period) and unavailability ( famine period)
generates unbalanced growth. During the excess of external carbon substrate, the
growth of biomass and storage of polymer occur simultaneously.

Production of PhB from Waste material
A major limiting factor in the development of biodegradable polyesters is the expense
associated with the carbon substrate used in the fermentation, which can account for
up to 50% of the overall production cost of PHB. The PHB production schemes based
on relatively inexpensive agricultural sources may contribute significantly to lower
manufacturing costs (Hass et al., 2008).