Biogas valorization via continuous polyhydroxybutyrate production by Methylocystis hirsuta in a bubble column bioreactor

Sustainable Process for the Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from Renewable Resources: A Simulation Study

“…The productivities of biomass (p-BIO) and PHB- co -HV (p-PHB- co -HV) and the amount of biomass (BIO) at the end of the growth and accumulation cycles (after 20 and 15 days, respectively) were assessed, as well as the fraction of poly(3-hydroxybutyrrate- co -3-hydroxyvalerate) into the total suspended solids (%PHB- co -HV). Moreover, the production of biopolymers per unit of methane fed (sPHB- co -HV) was determined, and the methane-utilizing capacity (EC-CH 4 ) was calculated according to the following equation (eq ) EC − C H 4 = Q ( C C H 4 , in − C C H 4 , out ) V where C CH 4 ,in and C CH 4 ,out are the methane concentrations in the inlet and outlet streams, Q is the total inlet gas flow rate, and V is the volume of the reactor.…”

“…Since fossil-based plastics are persistent and do not degrade in the environment, their overproduction has negatively impacted the environment, being today one of the leading causes of global pollution. − Many effects have been observed on the food chain, human health, and ecosystem stability and as a result of plastic pollution of land, air, and water . Therefore, the scientific community is nowadays challenging the development of an effective alternative to petrochemical plastics, such as biopolymers. , Among them, polyhydroxyalkanoates (PHAs) are very attractive as they are biodegradable and can be produced biologically by many bacteria and archaea as PHA granules inside of their cytoplasm when subjected to nutrient starvation. ,− Anyway, according to the most recent reports on bioplastics, PHAs only represent 1.8% of the global production capacities because of the many factors that hinder their market spread, including the low productivities, the poor scalability of the process, the high market price, and the low quality of the most produced homopolymer, namely, poly­(3-hydroxybutyrate) (PHB). ,− For instance, some industries produce PHB for applications in packaging and drugs at a pilot scale using expensive substrates, which account for 40% of the final price and applying cost-intensive extraction techniques. , In this context, it has been reported that the use of natural gas (i.e., methane) as a carbon source could lead to PHA accumulation in Type II methanotrophs, reducing the total cost by up to 30–35%. , Anyway, although PHB can be compared to the commercial polypropylene (PP), it still presents many disadvantages: it is stiffer and more brittle, has a lower resistance to solvents, and a lower extension to break than PP. − Nevertheless, the major obstacle in the applications of PHB is the narrow difference between its melting point (typically around 180 °C) and the temperature at which degradation begins (typically around 200 °C) . These similar values can make polymer processing (e.g., applying the melt-extrusion technology) complex.…”

“… 3 , 6 − 10 Anyway, according to the most recent reports on bioplastics, PHAs only represent 1.8% of the global production capacities because of the many factors that hinder their market spread, including the low productivities, the poor scalability of the process, the high market price, and the low quality of the most produced homopolymer, namely, poly(3-hydroxybutyrate) (PHB). 8 , 11 − 13 For instance, some industries produce PHB for applications in packaging and drugs at a pilot scale using expensive substrates, which account for 40% of the final price and applying cost-intensive extraction techniques. 11 , 14 In this context, it has been reported that the use of natural gas (i.e., methane) as a carbon source could lead to PHA accumulation in Type II methanotrophs, reducing the total cost by up to 30–35%.…”

Biotransformation of Methane and Carbon Dioxide Into High-Value Products by Methanotrophs: Current State of Art and Future Prospects

“…Methanotrophs also synthesize poly-β-hydroxybutyrate (PHB) (Methylosinus trichosporium, Methylocystis parvus, Methylocystis hirsuta), a potential replacement of conventional plastic owing to its biocompatible and biodegradable characteristics (Rodríguez et al, 2020). Single cell proteins, a major methanotrophic-product (Methylococcus capsulatus, Methylomonas sp., Methylocystis sp.…”

“…They are suitable for application when the requirement is to maintain directional flow and circulation, efficient mass transfer and heat transfer, especially while working with gas fermentation systems. Their application has mostly been reported for PHB production by methanotrophs (Ghoddosi et al, 2019;Rodríguez et al, 2020). Vertical tubular loop bioreactors have also been reported for gas fermentation.…”