Synthesis and properties of a novel biosuperabsorbent from alkali soluble Rhizomucor pusillus proteins

A novel biosuperabsorbent protein hydrogel was prepared from protein-rich alcoholic–alkali soluble parts of zygomycete Rhizomucor pusillus biomass. The fungal protein content was 46.8%, and the lipid content was 13.1%. Extraction of protein from this microorganism through the method applied prevents protein decomposition, resulting in maximum yield. After alcoholic–alkaline extraction, the proteins from the biomass were acylated using ethylenediaminetetraacetic dianhydride and subsequently treated with glutaraldehyde as a crosslinker for further experiments. Thermal consistency was investigated by means of two different methods: thermal denaturation via differential scanning calorimetry and thermal decomposition study via thermogravimetric analysis. The swelling behaviour of the crosslinked hydrogel was measured in deionised water, 0.9% NaCl solution and synthetic urine, which were 87.6, 43 and 38.6 g/g water after 24 h, respectively. Moreover, the isoelectric point (pI) of the hydrogel was determined as pH = 8 by studying swelling behaviour at different pHs. In addition, the dependencies of the swelling behaviour with regard to the chemical modification, the ionic strength, the degree of crosslinking, as well as water absorbency with or without load were studied.