Inhibition of bacilli in industrial starches by nisin

Abstract

The properties of Bacillus coagulans and of other bacilli that contaminate paper and paperboard manufacturing processes were investigated under simulated industrial conditions. Nisin (0.05 to 0.125 microg ml(-1) blocked growth of indigenous bacilli that contaminate sizing starches. B. coagulans starch isolates, B. licheniformis, B. amyloliquefaciens, and B. stearothermophilus grew at > or = 50 degrees C in industrial starch and produced alpha-glucosidase and cyclodextrins. The industrial isolates and reference strains of B. amyloliquefaciens, B. cereus, B. coagulans, B. flexus, B. licheniformis, B. pumilus, B. sporothermodurans, B. stearothermophilus and Alicyclobacillus acidoterrestris were inhibited by < or = 0.125 microg of nisin on agar. B. coagulans and B. stearothermophilus were similarly inhibited by < or = 0.025 microg of nisin ml(-1) and by 3 microg of the biocide DBNPA ml(-1) in industrial starch. B. licheniformis and B. amyloliquefaciens strains were less sensitive. About 40% of nisin added to starch was retained after cooking. Fifty percent of the nisin remained active after 11 h of storage at 60 degrees C. The results show that nisin has potential as a preservative for modified industrial starches.