Inhibition of bacilli in industrial starches by nisin

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 mug ml(-1)) blocked growth of indigenous bacilli that contaminate sizing starches. B. coagulans starch isolates, B. licheniformis, B. amyloliquefaciens, and B. stearothermophilus grew at greater than or equal to 50 degreesC 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 less than or equal to0.125 mug of nisin on agar. B. coagulans and B. stearothermophilus were similarly inhibited by less than or equal to0.025 mug of nisin ml(-1) and by 3 mug 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 degreesC. The results show that nisin has potential as a preservative for modified industrial starches.