In food industry, Bacillus species are encountered in deteriorating many food products thus shortening their shelf-life. Moreover, Bacillus cereus and the subtilis group (Bacillus subtilis, Bacillus licheniformis, and Bacillus pumilus) have been recognized as food poisoning agents. Lysozyme peptides preparation (LzP) is a commercially available as a natural food preservative. Although, UP derived from lysozyme yet it showed only 11% of the lysozyme lytic activity. UP at a concentration of 100 mu g ml(-1) completely inhibited B. subtilis, B. licheniformis, R megaterium, B. mycoides, B. pumilus, B. coagulans, B. amyloliquefaciens, B. polymexa and B. macerans. However, B. cereus and B. stearothermophilus showed a slightly higher resistance. Interestingly, UP at concentration >= 10 mu g ml(-1) showed inhibitory effect on both vegetative and spore forms of B. subtilis. Moreover, UP was stable at 95 degrees C for 30 min and at different pH values (4.5-7). In conclusion, UP may be useful to control growth of Bacillus spoilage organisms. (c) 2005 Elsevier Ltd. All rights reserved.