Leandro1, 2, R. Shirley1, 2, M. Teles1, 2, R. Machado3, M. Mateus1, H. Pinheiro1 , M. Sapatinha4, C. Pires4, I .Marmelo4, A. Marques4 , M.M.R. da Fonseca1,2, Maria Teresa Cesário1, 2
1.iBB-Institute for Bioengineering and Biosciences, Bioengineering Department, Instituto Superior Técnico, Universidade de Lisboa – Portugal
2.Associate Laboratory i4HB- Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa – Portugal
3.Cerena- Centro de Recursos Naturais e Ambiente, Chemical Engineering Department, Instituto Superior Técnico, Universidade de Lisboa- Portugal
4.IPMA- Instituto Português do Mar e Atmosfera, Lisboa-Portugal
Ulva lactuca, known as sea-lettuce, is a common macroalga associated with green tides in coastal areas. It contains approx. 35% polysaccharides and 15% proteins and its upgrade to valuable bioproducts is sought.
Protein extraction from Ulva was carried out in a pilot-plant using a conventional, green method. Protein extracts were processed to produce a protein-rich ingredient to be included in aquafeed. The produced extracts were characterized in terms of peptide and amino acid profiles, and antioxidant activity.
Alternative carbon sources are being screened to decrease production costs of the microbial polyesters polyhydroxyalkanoates (PHAs). After protein extraction Ulva residues with 25-40% carbohydrate content can be used as a carbon platform for poly-3-hydroxybutyrate (P3HB) production. Glucose-rich liquors were produced from Ulva residues and used as C-source by the halophilic bacterium Halomonas elongata DSM 2581T to produce P3HB. This bacterium was selected for its ability to synthesize PHAs under high salt concentrations, allowing the use of open cultivations and potentially decreasing sterilization-related costs. A combined hydrolysis of acidic thermal treatment followed by enzymatic hydrolysis with cellulolytic enzymes, yielded a liquor with 10-12 g/L total sugars and negligible amounts of the microbial growth inhibitor 5-hydroxymethylfurfural. After a concentration step, the hydrolysate was assessed for P3HB production by H. elongata. Bioreactor (2L) cultivations in the fed-batch mode were carried using the hydrolysate from Ulva residues as feed. A maximum P3HB production of 9.7 g/L, 24.3% P3HB content and 0.25 g/(L.h) productivity were attained. Gluconic acid was observed to be simultaneously produced.