Gang Wang,Quancheng Shu,Jinzhi Sun,Yucan Liu,Xiaoyong Yang,Hao Lin,Jing Ding,Yanxiang Zhang,Lijuan Lan,Hongwei Sun
To recycle the nutrients in spiramycin (SPM) fermentation residue (SFR) through biological methods, acid hydrothermal treatment (AHT) was employed as pretreatment to enhance SFR biodegradability. The results showed that the degradation rate of residual SPM in SFR reached 100% after 120 min at 100℃ and 0.30 M acid with a 30.5% and 89.7% increase in proteins and polysaccharides, respectively. The SPM degradation was faster at higher acidity and temperature. However, elevated SPM concentration and the presence of protein, humic acid, and polysaccharide inhibited SPM degradation. The disintegration of SFR was evidenced by changes in its microstructure and could be predicted through the release of dissolved organic matter. Eight major SPM intermediates were identified with lower mutagenicity and antibacterial activity testing against Staphylococcus aureus . These results demonstrate that AHT not only disintegrates SFR but also degrades the residual SPM antibiotics, which implies the possibility for practical applications.
Susceptibility of traditional hydrogels to water leads to the deterioration of their mechanical properties and dimensional instability. Inspired by bone tissues, here, we report a nonswellable gradient hydrogel with adjustable mechanical properties via a simple acid-heat treatment of polyamide-based hydrogels. Both the hydrophilicity/hydrophobicity and crosslinking degree of the gel can be simultaneously regulated by taking advantage of the conversion of amide groups to imide groups in the hydrogel. A gradient imide structure is formed with a dense layer near the surface of the gel. The resultant hydrogel has no size change both in water and 0.9 wt% NaCl solution while it shows high strength with a compressive stress of 70 MPa at 70% strain at a higher imidization degree. At a lower imidization degree, the gel has excellent fatigue resistance and resilience and can return to its original state after 5 cycles of 90% strain.
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