The influence of pH and monovalent/divalent cations on the structural and physicochemical properties of myofibrillar protein from silver carp.

The present study aimed to investigate effects of pH and monovalent (Na+ and K+)/divalent (Ca2+ and Mg2+) cations on the structural and physicochemical properties of myofibrillar protein (MP) from silver carp. MP treated with divalent cation had lesser change for the structure than that treated with monovalent cation. Ca2+-ATPase activity of MP treated with monovalent cation was increased firstly and then decreased, while that treated with divalent cation was decreased with increasing ionic strength. Surface hydrophobicity and Z-average of MP treated with divalent cations was lower than that with monovalent cations, while they decreased and then increased with the pH shifting from 3.0 to 9.0. Zeta potential of MP was increased and then decreased with increasing the pH but decreased and then increased with increasing ionic strength. In general, the pH and monovalent/divalent cations could cause various hydrophobic and electrostatic interactions, resulting in changes of the physicochemical properties of MP.

Effects of ε-Poly-L-Lysine Combined with Wuyiencin as a Bio-Fungicide against Botryris cinerea.

This study mainly evaluated the broad-spectrum fungicidal activity of ε-poly L lysine (ε-PL) against 12 pathogenic fungi. We further demonstrated synergistic antifungal activity of ε-PL combined with wuyiencin against Botryris cinerea. The combined bio-fungicide achieved an inhibition rate of 100% for mycelial growth using ε-PL at 500 µg/mL + wuyiencin at 50 µg/mL and for spore germination using ε-PL at 200 µg/mL + wuyiencin at 80 µg/mL in vitro. This synergistic spore and mycelia-damaging effect of the combination was confirmed using scanning electron microscopy. In vivo assays with combined bio-fungicide (1500 µg/mL ε-PL + 60 µg/mL wuyiencin) on detached leaves showed depressed growth and development of the spores of B. cinerea. The synergistic effect was further tested in combinations of ε-PL with wuyiencin by measuring the fractional inhibition concentration index (FICI) value below 0.5. Moreover, ε-PL and wuyiencin inoculation before B. cinerea infection significantly increased the superoxide dismutase, peroxidase, catalase, and phenylalanine ammonia-lyase activities, which suggested their involvement in tomato defense responses to disease to minimize damage to B. cinerea. These findings revealed that a combined bio-fungicide comprising ε-PL and wuyiencin had a good prospect for controlling plant fungal disease.