Polyhydroxyalkanoate Biosynthesis at the Edge of Water Activity-Haloarchaea as Biopolyester Factories

Abstract

Haloarchaea, the extremely halophilic branch of the Archaea domain, encompass a steadily increasing number of genera and associated species which accumulate polyhydroxyalkanoate biopolyesters in their cytoplasm. Such ancient organisms, which thrive in highly challenging, often hostile habitats characterized by salinities between 100 and 300 g/L NaCl, have the potential to outperform established polyhydroxyalkanoate production strains. As detailed in the review, this optimization presents due to multifarious reasons, including: cultivation setups at extreme salinities can be performed at minimized sterility precautions by excluding the growth of microbial contaminants; the high inner-osmotic pressure in haloarchaea cells facilitates the recovery of intracellular biopolyester granules by cell disintegration in hypo-osmotic media; many haloarchaea utilize carbon-rich waste streams as main substrates for growth and polyhydroxyalkanoate biosynthesis, which allows coupling polyhydroxyalkanoate production with bio-economic waste management; finally, in many cases, haloarchaea are reported to produce copolyesters from structurally unrelated inexpensive substrates, and polyhydroxyalkanoate biosynthesis often occurs in parallel to the production of additional marketable bio-products like pigments or polysaccharides. This review summarizes the current knowledge about polyhydroxyalkanoate production by diverse haloarchaea; this covers the detection of new haloarchaea producing polyhydroxyalkanoates, understanding the genetic and enzymatic particularities of such organisms, kinetic aspects, material characterization, upscaling and techno-economic and life cycle assessment.

Advances in Polyhydroxyalkanoate (PHA) Production, Volume 2

“…These earliest organisms on earth live in challenging habitats at salinities between 100 and 300 g/L NaCl and could potentially beat established PHA production strains in future due to several benefits: cultivations in highly saline media can be run at reduced sterility by preventing the growth of non-halophilic contaminants; the high intra-cellular osmotic pressure of haloarchaea simplifies the release of intracellular PHA granules by hypo-osmotic cell disintegration; many haloarchaea convert diverse inexpensive carbonaceous waste materials as feedstocks for growth and PHA production, which combines PHA production with waste upcycling; some haloarchaea are even said to produce high-quality copolyesters from simple, structurally unrelated inexpensive substrates; finally, PHA biosynthesis often takes place in parallel to the biosynthesis of additional marketable compounds, such as polysaccharides, antibiotics, or pigments. The current knowledge on PHA production by haloarchaea is reviewed in this article, covering the quest for new PHA-producing haloarchaea, their genetic and enzymatic idiosyncrasies, the properties of haloarchaeal PHA, successful attempts for upscaling PHA production by haloarchaea, and techno-economic and life cycle assessments of selected processes [20].…”

Current developments on polyhydroxyalkanoates synthesis by using halophiles as a promising cell factory

“…At present, there are many reviews already published on PHA synthesis, and its related challenges and future applications [15,[20][21][22]. However, most of these reviews focus on non-halophiles.…”

Recent Progress in Polyhydroxyalkanoates‐Based Copolymers for Biomedical Applications

“…The biopolyester polyhydroxyalkanoates (PHA), which could be obtained from bacteria and archaea, have been extensively studied by experts and scholars from different disciplines, including molecular biologists, polymer experts, biochemists, microbiologists, chemists, and medical researchers . PHAs, as a family of diverse biopolyesters, include poly(3‐hydroxybutyrate‐ co ‐3‐hydroxyvalerate) (PHBV), poly(3‐hydroxybutyrate‐ co ‐3‐hydroxyhexanoate) (PHBHHx), poly (3‐hydroxyoctanoate) (PHO), poly(4‐hydroxybutyrate) (P4HB), and poly(3‐hydroxybutyrate) (P3HB) .…”