Bioprocess development for the production of poly(3-hydroxybutyrate) using the invasive macroalgae Rugulopteryx okamurae

The brown macroalga Rugulopteryx okamurae was used to produce a sugar-rich hydrolysate, which served as a carbon source in Paraburkholderia sacchari DSM 17165 cultures for the production of poly(3-hydroxybutyrate) (PHB). Biological pretreatment of R. okamurae using the fungal strains Aspergillus awamori and Aspergillus oryzae in solid-state fermentation (SSF) was employed to produce alginate lyase (24 IU/g_biomass) and protease (20 IU/g_biomass). The fermented solids were used for enzymatic hydrolysis in combination with a commercial cocktail of enzymes containing cellulase and hemicellulase. SSF of the macroalgae for 72 h by A. oryzae, followed by enzymatic saccharification for 48 h, resulted in a total reducing sugars (TRS) concentration of around 120 mg_TRS/g_biomass. Conducting a bioreactor batch fermentation on macroalgae-derived hydrolysate for PHB production by P. sacchari, consuming 51 g/L of glucose, resulted in 43.3 g/L of dry cell weight with 28.4 % PHB content (12.3 g/L PHB). This study demonstrated the feasibility of exploiting macroalgae as a feedstock for PHB production.