Dong Ming-sheng

Ginger rhizome as a potential source of milk coagulating cysteine protease

A milk coagulating protease was purified ∼10.2-fold to apparent homogeneity from ginger rhizomes in 34.9% recovery using ammonium sulfate fractionation, together with ion exchange and size exclusion chromatographic techniques. The molecular mass of the purified protease was estimated to be ∼36kDa by SDS-PAGE, and exhibited a pI of 4.3. It is a glycoprotein with 3% carbohydrate content. The purified enzyme showed maximum activity at pH 5.5 and at a temperature of ∼60°C. Its protease activity was strongly inhibited by iodoacetamide, E-64, PCMB, Hg(2+) and Cu(2+). Inhibition studies and N-terminal sequence classified the enzyme as a member of the cysteine proteases. The cleavage capability of the isolated enzyme was higher for α(s)-casein followed by β- and κ-casein. The purified enzyme differed in molecular mass, pI, carbohydrate content, and N-terminal sequence from previously reported ginger proteases. These results indicate that the purified protease may have potential application as a rennet substitute in the dairy industry.

In vitro antibiofilm activity of the melanin from Auricularia auricula, an edible jelly mushroom

A melanin derived from Auricularia auricula was characterized based on ultraviolet-visible (UV), infrared (IR), electron paramagnetic resonance (EPR) spectra and chemical tests. The antibiofilm activity of the isolated A. auricula melanin against Escherichia coli K-12, Pseudomonas aeruginosa PAO1 and P. fluorescens P-3 was examined using crystal violet and LIVE/DEAD BacLight staining as well as confocal laser scanning microscopy (CLSM). The results showed that A. auricula melanin could inhibit significantly biofilm formation of E. coli K-12, P. aeruginosa PAO1 and P. fluorescens P-3, while no inhibitory effects on growth were found. CLSM analysis showed that A. auricula melanin treatment resulted in thinner and looser biofilm compared with the control. The current study reveals for the first time the antibiofilm activity of melanin derived from A. auricula.