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Biocatalysis and Agricultural Biotechnology
Volume 18, 2019, 101013

Incorporation of microencapsulated Lactobacillus rhamnosus into infant-foods inhibit proliferation of toxicogenic Bacillus cereus strains

Mohamed AliAbdel-Rahmana, Zeinab I.Sadekb, Mohamed S.Azaba, Osama M.Darweshc, Mahmoud S.Hassana

Botany and Microbiology Dept, Faculty of Science (Boys-branch), Al-Azhar University, Nasr City, PN. 11884, Cairo, Egypt.

Abstract

Considering the hygienic quality of infant-food is of great important, especially it is the primary source of kids nutrition. Bacillus cereus has been recognized as a serious food-borne pathogen, causing outbreaks due to the produced enterotoxins including cytotoxin K (CytK), non-hemolytic enterotoxin (Nhe) and hemolysin BL (Hbl). In this study, two bacterial isolates, carrying the virulence encoding genes cytK, nheC, and hblA, were obtained from infant-foods. Using 16S rDNA sequence analysis, they were identified as Bacillus cereus MH031700 and MH031701. Then, they were tested for the antagonistic effect of some lactic acid bacterial strains. Results showed that cell free supernatant from Lactobacillus rhamnosus B-445 exhibited the highest antagonistic activity. In addition, this strain have reduced the growth of the toxicogenic Bacillus spp in mixed cultures. In further experiments, proliferation of B. cereus strains was evaluated in presence/absence of microencapsulated or spray-dried L. rhamnosus B-445 in formulated infant-food mixtures. Microencapsulated cells exhibited higher effeciency for growth inhibition than spray dried cells. Incorporating microencapsulated or spray dried L. rhamnosus B-445 not only inhibited the proliferation of B. cereus strains that existed in infant-foods but also it reduced their count from ∼ Log 3.0 to ∼ Log 2.0 after 2 and 3 h at room temperature (25 °C), respectively. Similar results were achieved at low temperature (7.0 ± 2.0 °C) but after 4 and 8 h, respectively. Our results showed the potential efficiency of L. rhamnosus B-445 in suppressing toxicogenic B. cereus strains by its supplementation into infant-foods.

Graphical abstract

Keywords: Infant-food, Microencapsulation, Spray dried probiotics, Bacillus cereus, Lactobacillus rhamnosus B-445, Biocontrol agents.

 
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