Moist olive pomace (MOP) is a high moisture content by-product of the olive oil industry.
Managing this recalcitrant residue (transport, storage, and drying) is a priority demanding
investment in finding alternative valorisation routes. In this context, the biosynthesis of
xanthan gum (XG) incorporating MOP in the substrate (0.0 %, 5.0 %, 10.0 %, 15.0 %, 20.0 %,
25.0 %, 30.0 % and 50.0 %) to induce bacterial stress was attempted. XG biosynthesis yield
was quantified, and the product was characterised by structural analysis (FTIR), thermal
behaviour (TG), rheology and antioxidant capacity. Relative to the control (sample with no
added MOP), a significant increase in XG biosynthesis was found for concentrations up to
30.0 % MOP. In particular, for XG produced with 15 % MOP, a 50.91 % (p < 0.0001) increase
was achieved, together with 395.78 % for viscosity. In general, XG produced with MOP
presence showed antioxidant activity, a value-added property, especially for applications
in the food, pharmaceutical and cosmetic areas. The results indicated that the stress
imposed by the MOP induced a microbial response leading to XG production increase,
structural and viscosity modifications, and antioxidant properties incorporation. Overall,
this work points out a new MOP application contributing to the sustainability of the olive
oil productive chain from a biobased circular economy perspective.
The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020), and SusTEC (LA/P/0007/2021). Project OleaChain “Skills for sustainability and innovation in the value chain of traditional olive groves in the Northern Inland of Portugal” (NORTE-06-3559-FSE-000188) for P.J.L. Crugeira and A.I.G. Rodrigues contracts. FCT for the PhD research grant of H.H.S. Almeida (SFRH/BD/148124/2019). National funding by FCT, P.I., through the institutional scientific employment program contract of A. Santamaria-Echart.
