Grafting of PHGH on lignin improves the antibacterial activity and the usage as an additive of starch film

The insufficient bacteriostatic capacity of lignin greatly limits its application performance in the packaging and medical fields. Herein, a lignin with significantly enhanced antibacterial activity was prepared, in which PHGH (polyhexamethylene guanidine hydrochloride) was chosen to be grafted onto lignin, initiated by the glyoxal induced cross-linking. The grafting of PHGH on the lignin (PHGH-m-lignin) was confirmed by the FTIR, ¹H- and ³¹P NMR spectra. The diameter size and zeta potential of PHGH-m-LNP were evaluated. Compared with that (199.96 nm) of pristine LNP, the diameter size of PHGH-m-LNP decreased to 71.44 nm, and the zeta potential increased to − 25.6 mV from − 30.1 mV. The results of antibacterial activity showed that the PHGH-m-LNP exhibited an excellent antibacterial activity (>99.99 %) towards E.coli. AFM images disclosed the physically antibacterial mechanism of PHGH-m-LNP. For the application, different concentrations of PHGH-m-lignin nanofiller (PHGH-m-LNP) were used to fabricate starch films via casting method. The PHGH-m-LNP could confer the starch film an exceptional antimicrobial activity (antibacterial activities = 98.84 %) at the addition level of 1 % (wt). In addition, the hydrophobicity and UV shielding capacity of starch film were enhanced, with the decreased maximum thermal degradation rate. Therefore, a new way to improve the antibacterial activity of lignin is provided, which is greatly significant for boosting the high-value application potential of lignin in the packaging and medical fields.