Table 1.

Challenges for producing cost competitive PHA.

Problems	Reasons	Solutions	Reference
High energy demands	Sterilization and intensive aeration	Unsterile and micro-aerobic processes	[17]
Low substrates to PHA conversions	Substrates are consumed for other purposes	Deletion or weakening PHA unrelated pathways	[18], [19]
Unstable PHA structures	Multiple pathways consuming PHA precursors	Deletion or weakening PHA unrelated pathways	[19], [20]
Unstable batch Mw	Unstable PHA synthase activity	Controlling PHA synthase activity	[8], [10]
Slow growth	Binary fission et al.	Multiple fission et al.	[21]
Discontinuous processes	Avoid possible contamination	Use contamination resistant strains	[16], [17], [22]
Expensive downstream	Complexity to extract and purify products	Morphology engineering	[23], [24]