Abstract
The increasing impact of plastic materials on the environment is a growing global concern. In regards to this circumstance, it is a major challenge to find new sources for the production of bioplastics. Poly-β-hydroxybutyrate (PHB) is characterized by interesting features that draw attention for research and commercial ventures. Indeed, PHB is eco-friendly, biodegradable, and biocompatible. Bacterial fermentation processes are a known route to produce PHB. However, the production of PHB through the chemoheterotrophic bacterial system is very expensive due to the high costs of the carbon source for the growth of the organism. On the contrary, the production of PHB through the photoautotrophic cyanobacterium system is considered an attractive alternative for a low-cost PHB production because of the inexpensive feedstock (CO2 and light). This paper regards the evaluation of four independent strategies to improve the PHB production by cyanobacteria: (i) the design of the medium; (ii) the genetic engineering to improve the PHB accumulation; (iii) the development of robust models as a tool to identify the bottleneck(s) of the PHB production to maximize the production; and (iv) the continuous operation mode in a photobioreactor for PHB production. The synergic effect of these strategies could address the design of the optimal PHB production process by cyanobacteria. A further limitation for the commercial production of PHB via the biotechnological route are the high costs related to the recovery of PHB granules. Therefore, a further challenge is to select a low-cost and environmentally friendly process to recover PHB from cyanobacteria.
Highlights
Nowadays, plastic materials are widely used and essential components of product packaging, cars, household/office appliances, computer equipment, and medical devices [1]
A PHB production fraction in cyanobacteria as high as 71% may be produced in Nostoc muscorum Agardh cultures carried out in a medium supplemented with glucose, acetate, and valerate coupled with nitrogen and phosphate limitation [52]
Poly-β-hydroxybutyrate (PHB) is one of the best biodegradable polymers among those proposed as alternatives to conventional plastics
Summary
Plastic materials are widely used and essential components of product packaging, cars, household/office appliances, computer equipment, and medical devices [1]. Plastic production requires the processing of approximately 150 million tons of fossil fuels and a huge amount of waste is produced whose depolymerization can take thousands of years [2]. Plastics are biodegradable at a tunable rate depending on the surrounding environmental conditions (e.g., location or temperature) and on the material (http://www.european-bioplastics.org/). This group includes biodegradable biopolymer extracted from microorganisms (e.g., polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)). This group includes biodegradable biopolymer produced by a conventional synthesis of bio derived monomers (e.g., polylactic acid (PLA)). Biodegradable plastics altogether, including polylactic acid (PLA), polyhydroxyalkanoates (PHA), starch blends, and others, account for over 55.5 percent (over 1 million tons) of global bioplastics production capacities. Polyhydroxyalkanoates (PHAs) are the main blocks of biodegradable plastics They are polyesters produced by various microorganisms, such as cyanobacteria. Key physical features of PHBs are a melting temperature of about 177 ◦ C, glass transition temperature of about 2 ◦ C, crystallinity of about 60%, tensile strength of about 43 MPa, and extension to break of about 5% [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
