Haloarchaea as Cell Factories to Produce Bioplastics

Abstract

Plastic pollution is a worldwide concern causing the death of animals (mainly aquatic fauna) and environmental deterioration. Plastic recycling is, in most cases, difficult or even impossible. For this reason, new research lines are emerging to identify highly biodegradable bioplastics or plastic formulations that are more environmentally friendly than current ones. In this context, microbes, capable of synthesizing bioplastics, were revealed to be good models to design strategies in which microorganisms can be used as cell factories. Recently, special interest has been paid to haloarchaea due to the capability of some species to produce significant concentrations of polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), and polyhydroxyvalerate (PHV) when growing under a specific nutritional status. The growth of those microorganisms at the pilot or industrial scale offers several advantages compared to that of other microbes that are bioplastic producers. This review summarizes the state of the art of bioplastic production and the most recent findings regarding the production of bioplastics by halophilic microorganisms with special emphasis on haloarchaea. Some protocols to produce/analyze bioplastics are highlighted here to shed light on the potential use of haloarchaea at the industrial scale to produce valuable products, thus minimizing environmental pollution by plastics made from petroleum.

Characterization of Polyhydroxybutyrate, PHB, Synthesized by Newly Isolated Haloarchaea Halolamina spp.

“…Extremophilic microorganisms, particularly haloarchaea, show all the optimum features to be a good candidate to produce PHA on a large scale: Microbial growth can be achieved by using waste carbon sources and there is no need for medium sterilization, minimal risk of contamination by other microorganisms, use of brines or seawater for medium preparation, recovery of the salts used in the medium, and a simple cell lysis process with water to harvest the polymer granules [ 7 , 8 ]. Consequently, as bioplastic producers, haloarchaea have advantages over other bacterial strains, hence minimizing the production cost of PHA [ 9 , 10 ].…”

Isolation, Phylogenetic and Gephyromycin Metabolites Characterization of New Exopolysaccharides-Bearing Antarctic Actinobacterium from Feces of Emperor Penguin

“…Furthermore, genomic mining of strain NJES-13 revealed one loci harboring genes assigned to PHA biosynthesis pathway. Bacterial PHAs are used to store carbon and energy, and highlight the huge talent for the production of biodegradable bioplastics [ 37 , 38 ]. These encoding genes included acetoacetyl-CoA reductase, poly(R)- hydroxyalcanoic acid synthase and an ORF-encoding phasin protein responsible for PHA granule formation.…”

Ubiquitousness of Haloferax and Carotenoid Producing Genes in Arabian Sea Coastal Biosystems of India

“…Haloferax species are of particular interest as they are hyper producers of bacterioruberin with high antioxidant and pharmaceutical applications [ 64 , 65 , 66 ]. Haloferax can also convert cheese whey/olive mill wastewater into poly (3-hydroxybutyrate-co-3-hydroxyvalerate), which shows potential applications as biodegradable biopolymer [ 67 , 68 , 69 ]. Furthermore, extreme salt tolerance is a desirable attribute for the industrial-scale production of carotenoids or whole-cell biocatalysts due to its ease in extraction, tolerance to salinity, and an array of biological applications [ 4 , 5 , 6 , 66 ].…”