Marine Purple Photosynthetic Bacteria as Sustainable Microbial Production Hosts

Abstract

Photosynthetic microorganisms can serve as the ideal hosts for the sustainable production of high-value compounds. Purple photosynthetic bacteria are typical anoxygenic photosynthetic microorganisms and are expected to be one of the suitable microorganisms for industrial production. Purple photosynthetic bacteria are reported to produce polyhydroxyalkanoate (PHA), extracellular nucleic acids and hydrogen gas. We characterized PHA production as a model compound in purple photosynthetic bacteria, especially focused on marine strains. PHA is a family of biopolyesters synthesized by a variety of microorganisms as carbon and energy storage materials. PHA have recently attracted attention as an alternative to conventional petroleum-based plastics. Production of extracellular nucleic acids have been studied in Rhodovulum sulfidophilum, a marine purple non-sulfur bacterium. Several types of artificial RNAs have been successfully produced in R. sulfidophilum. Purple photosynthetic bacteria produce hydrogen via nitrogenase, and genetic engineering strategies have been investigated to enhance the hydrogen production. This mini review describes the microbial production of these high-value compounds using purple photosynthetic bacteria as the host microorganism.

Keywords: extracellular nucleic acids; hydrogen; polyhydroxyalkanoate; purple photosynthetic bacteria; sustainable production.

Figure 1

Sustainable production of high-value compounds in marine purple photosynthetic bacteria. PHA was produced from acetyl-CoA in tree steps (A). Extracellular nucleic acids were produced in the process of GTA-like particle production controlled by CtrA (B). The nitrogenase complex is composed of dinitrogenase reductase and dinitrogenase. Nitrogenase catalyzes the proton reduction to hydrogen as well as the reduction of nitrogen to ammonia (C).