Rope-Producing Strains of Bacillus spp. from Wheat Bread and Strategy for Their Control by Lactic Acid Bacteria

Abstract

Two types of white wheat bread (high-and low-type loaves) were investigated for rope spoilage. Thirty of the 56 breads tested developed rope spoilage within 5 days; the high-type loaves were affected by rope spoilage more than the low-type loaves. Sixty-one Bacillus strains were isolated from ropy breads and were characterized on the basis of their phenotypic and genotypic traits. All of the isolates were identified as Bacillus subtilis by biochemical tests, but molecular assays (randomly amplified polymorphic DNA PCR assay, denaturing gradient gel electrophoresis analysis, and sequencing of the V3 region of 16S ribosomal DNA) revealed greater Bacillus species variety in ropy breads. In fact, besides strains of B. subtilis, Bacillus licheniformis, Bacillus cereus, and isolates of Bacillus clausii and Bacillus firmus were also identified. All of the ropy Bacillus isolates exhibited amylase activity, whereas only 32.4% of these isolates were able to produce ropiness in bread slices after treatment at 96°C for 10 min. Strains of lactic acid bacteria previously isolated from sourdough were first selected for antirope activity on bread slices and then used as starters for bread-making experiments. Prevention of growth of approximately 10 4 rope-producing B. subtilis G1 spores per cm 2 on bread slices for more than 15 days was observed when heat-treated cultures of Lactobacillus plantarum E5 and Leuconostoc mesenteroides A27 were added. Growth of B. subtilis G1 occurred after 7 days in breads started with Saccharomyces cerevisiae T22, L. plantarum E5, and L. mesenteroides A27.Ropiness is bacterial spoilage of bread that initially occurs as an unpleasant fruity odor, followed by enzymatic degradation of the crumb that becomes soft and sticky because of the production of extracellular slimy polysaccharides (15,43).The species involved in this type of spoilage of bread are primarily Bacillus subtilis and occasionally Bacillus licheniformis, Bacillus pumilus, and Bacillus cereus, even though some rope-producing Bacillus isolates are often not identified at the species level (9,22,41). It is well known that species differentiation within the genus Bacillus is very difficult because of the large number of species and the often incomplete descriptions of a number of newly reported species (19). For these reasons, molecular methods have been used increasingly to simplify characterization procedures in order to provide rapid and reliable identification or to validate phenotypically determined taxa. Among the molecular methods, the randomly amplified polymorphic DNA PCR (RAPD-PCR) assay, 16S ribosomal DNA (rDNA) PCR-denaturing gradient gel electrophoresis (DGGE) analysis, and 16S rDNA sequencing are considered reliable approaches to overcome most of the problems described above. In particular, RAPD-PCR analysis was developed to compare intra-and interspecific differences among Bacillus strains (5, 40), and this method has also been shown to be suitable for identifying a variety of Bacillus species (32). The second approach, DGG...

Screening for Bacillus Isolates in the Broiler Gastrointestinal Tract

“…Bacillus species are frequently found in food (9,14,46), which could facilitate their entry into the different gut ecosystems. Earlier studies have reported on the frequent isolation of B. cereus from human feces (11,65), and a recent study has reported the identification of B. subtilis, B. licheniformis, B. pumilus, and Bacillus fragilis in the cecum of rabbits and the role of sporulation by B. subtilis in the induction of gut-associated lymphoid tissue development (55).…”

Codominance of Lactobacillus plantarum and obligate heterofermentative lactic acid bacteria during sourdough fermentation

“…plantarum in sourdough production is not only important for the generation of acids, but also for several other positive effects expressed during fermentation. L. plantarum has been reported as inhibitor of rope-producing B. subtilis (Pepe et al, 2003;Menteş et al, 2007). It is able to produce bacteriocins, namely plantaricin (Todorov et al, 1999), and antifungal compounds (Lavermicocca et al, 2000;Magnusson et al, 2003;Ryan et al, 2008).…”

Polyphasic Screening, Homopolysaccharide Composition, and Viscoelastic Behavior of Wheat Sourdough from a Leuconostoc lactis and Lactobacillus curvatus Exopolysaccharide-Producing Starter Culture

“…The study extends current knowledge on the effect of exopolysaccharide production by cereal-associated lactic acid bacteria. (3,9,10,42,44,45). The LAB strains, complete with origins and references, are presented in Table S1 in the supplemental material.…”