Sustainable Biobased Protein Superabsorbents from Agricultural Co-Products
Time: Fri 2020-10-16 09.00
Subject area: Fibre and Polymer Science
Doctoral student: Antonio Jose Capezza , Polymera material, SLU
Opponent: Prof. Antonio Guerrero, Sevilla University
Supervisor: Professor Mikael S. Hedenqvist, Polymera material; Professor Eva Johansson, SLU
The preparation of sustainable protein superabsorbents from agricultural industry side-streams is reported. Wheat gluten (WG), a co-product from the ethanol/starch industry, was processed into foams with sponge-like behavior and high liquid uptake. The materials were obtained by phase-separation of aqueous WG dispersions followed by ambient drying, or by lyophilization. The use of a natural and non-toxic cross-linker (genipin) resulted in foams with high water swelling properties (~18 g/g in 10 min). The rapid swelling may be of use in bio-based foams in e.g., sanitary pads.
As an alternative, potato protein concentrate (PPC, side-stream from the starch industry), was functionalized and prepared as particles. The liquid swelling capacity was compared after acylation with five different agents. It is shown that the PPC can be acylated to replicate the chemistry of synthetic superabsorbent polymers (SAP), showing water swelling capacity >10 g/g. The acylation (using EDTAD) of WG suspensions resulted in protein particles with water and saline uptake of 22 and 5 g/g, respectively. Limited network stability was however observed when acylating WG in low-protein suspensions. This was addressed by mixing the acylated protein with genipin, which provided a stable protein network. The process gave functionalized particles with swelling capacity ~40 g/g and ~80 % retention of swelling in centrifuge retention tests.
The extrusion of WG showed that porous WG with water uptake of 500 % can be produced. Further, the scalability of PPC production was pilot-tested by functionalizing potato fruit juice (PFJ), containing the potato protein in its soluble state before the industrial drying used to obtain PPC. This resulted in water swelling capacities >10 g/g, which was comparable to the PPC-functionalized materials. The results pave the way for future optimization of high-throughput production techniques using protein sources in mass production of sustainable protein-based SAPs.