Palm kernel expeller (PKE), the by-product derived from the palm kernel oil milling industry, is commonly added to ruminant feed as a source of protein. Recent research has demonstrated that the enzymatically hydrolyzed protein is inhibitory to spore-forming bacteria including Bacillus cereus. The trypsin-hydrolyzed PKE peptide appears to disrupt the membrane integrity and inhibit the intracellular macromolecule metabolism of B. cereus. The addition of the PKE peptide (350 and 700 μg/ml) to B. cereus cultures triggered the efflux of K(+) and caused the depletion of the intracellular ATP. However, no proportional increase in cell's extracellular ATP was observed. Analysis of the biosynthesis of macromolecules demonstrated that RNA was affected by the PKE peptide. Results of this study suggest that the PKE peptide is bacteriostatic interfering with membrane integrity and forming membrane pores permitting the efflux of K(+) and interferes with intracellular biopolymer synthesis.
The goal of this study was to determine inhibitory effect of palm kernel expeller (PKE) peptides of different degree of hydrolysis (DH %) against spore-forming bacteria Bacillus cereus, Bacillus circulans, Bacillus coagulans, Bacillus licheniformis, Bacillus megaterium, Bacillus pumilus, Bacillus stearothermophillus, Bacillus subtilis, Bacillus thuringiensis, Clostridium perfringens; and non-spore-forming bacteria Escherichia coli, Lisinibacillus sphaericus, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella Typhimurium and Staphylococcus aureus.
Plants of the genus Zingiber (Family Zingiberaceae) are widely used throughout the world as food and medicinal plants. They represent very popular herbal remedies in various traditional healing systems; in particular, rhizome of Zingiber spp. plants has a long history of ethnobotanical uses because of a plethora of curative properties. Antimicrobial activity of rhizome essential oil has been extensively confirmed in vitro and attributed to its chemical components, mainly consisting of monoterpene and sesquiterpene hydrocarbons such as α-zingiberene, ar-curcumene, β-bisabolene and β-sesquiphellandrene. In addition, gingerols have been identified as the major active components in the fresh rhizome, whereas shogaols, dehydrated gingerol derivatives, are the predominant pungent constituents in dried rhizome. Zingiber spp. may thus represent a promising and innovative source of natural alternatives to chemical food preservatives. This approach would meet the increasing concern of consumers aware of the potential health risks associated with the conventional antimicrobial agents in food. This narrative review aims at providing a literature overview on Zingiber spp. plants, their cultivation, traditional uses, phytochemical constituents and biological activities.