Upgrading end-of-line residues of the red seaweed Gelidium sesquipedale to polyhydroxyalkanoates using Halomonas boliviensis

S Tůma; J K Izaguirre; M Bondar; M M Marques; P Fernandes; M M R da Fonseca; M T Cesário

doi:10.1016/j.btre.2020.e00491

Upgrading end-of-line residues of the red seaweed Gelidium sesquipedale to polyhydroxyalkanoates using Halomonas boliviensis

Biotechnol Rep (Amst). 2020 Jun 16:27:e00491. doi: 10.1016/j.btre.2020.e00491. eCollection 2020 Sep.

Authors

S Tůma¹, J K Izaguirre^{1

2}, M Bondar¹, M M Marques¹, P Fernandes^{1

3}, M M R da Fonseca¹, M T Cesário¹

Affiliations

¹ iBB- Institute for Bioengineering and Biosciences, Bioengineering Department, Instituto Superior Técnico, Universidade de Lisboa, Portugal.
² Neiker-Tecnalia, Basque Institute for Agricultural Research, Vitoria-Gasteiz, Spain.
³ DREAMS and Faculty of Engineering, Universidade Lusófona de Humanidades e Tecnologias, Lisboa, Portugal.

Abstract

Agar extraction from Gelidium and Gracilaria red seaweed species produces hundred thousand ton of carbohydrate-rich residues annually. Gelidium sesquipedale waste biomass obtained after agar extraction, still contained 44.2 % w/w total carbohydrates (dry-weight basis). These residues were biologically up-graded to poly-3-hydroxybutyrate (P3HB) after saccharification of their carbohydrate fraction to simple sugars. A combined hydrolysis treatment using sulfamic acid followed by enzymatic hydrolysis with cellulases produced a glucose-rich hydrolysate with a negligible content of inhibitors. With this treatment a sugar yield of circa 30 % (g glucose/g biomass) was attained. The algal hydrolysates were assessed as carbon source for the production of P3HB by the halotolerant bacteria Halomonas boliviensis. A cell concentration of 8.3 g L^-1 containing 41 % (w/w) of polymer and a yield (Y_P/S ) of 0.16 g_polymer/g_glucose were attained in shake flask assays. In this work, cellulose-rich seaweed waste was shown to be an upgradable, sustainable source of carbohydrates.

Keywords: AGU, AmyloGlucosidase Unit; AHG, anhydro-L-galactose; AOAC, Association of Official Agricultural Chemists; BHU (2), Biomass Hydrolysis Unit; CBU, CelloBiase Unit; CDW, cell dry weight; FID, flame ionization detector; FPU, Filter Paper Unit; Fr, Froude number; G. sesquipedale, Gelidium sesquipedale; Gelidium sesquipedale; H. boliviensis, Halomonas boliviensis; HMF, 5-hydroxymethyl furfural; Halomonas boliviensis; KNU, Kilo Novo alpha-amylase Unit; MSG, monosodium glutamate; Macroalgae residues; Mw, molecular weight; NABH, neoagarobiose hydrolase; NREL, National Renewable Energy. Laboratory; P3HB, poly-3-hydroxybutyrate; Poly-3-hydroxybutyrate; Seaweed residues; Waste seaweed; dw basis, dry weight basis.