Molecular screening of potential Bacillus species bacteriocin starter cultures isolated from Nigerian fermented

Abstract

Traditional fermented food condiments in Nigeria are majorly produced by using protein-rich leguminous seeds via spontaneous fermentation or back slopping. However, health risks such as the production of biogenic amines, presence of toxigenic genes and food borne pathogens remains major concerns of public health significance. Hence, the need for the production of safe condiments using non-pathogenic food-grade starter cultures. Isolation and characterization of organisms from spontaneously fermented condiments made from Parkia biglobosa, Ricinus communis, Pentaclethra macrophylla and Prosopis africana was done using standard methods. Phenotypic and biochemical characterizations was down using established protocols while molecular identification was done using 16S rRNA sequencing. Results obtained showed that the microbial load (cfu/ml) recorded from the spontaneously fermented condiments ranged from: 2.1×10⁷-5.2×10¹², 15.2×10⁷-4.4×10¹⁰, 4.4×10¹⁰-4.4×10¹² and 6.4×10⁷-1.6×10¹² for P. biglobosa, R. communis, P. macrophylla and P. africana respectively. Identification of isolates revealed Bacillus.  However, 22.8% of the Bacillus isolates harboured HblA and HblD genes while 40.9 % showed bands for the presence of HblC genes. In addition, the percentage occurrence of 18.1%, 27.2% and 50% was obtained for the presence of NheA, NheB and NheC genes respectively while none of the Bacillus isolates showed bands for the presence of Cytk and EM1 genes. More so, five Bacillus isolates were identified to be non-toxigenic, showing bands only for Bac, Osbo and Spas genes which are bacteriocin producing genes. Put together, the identified non-toxigenic food-grade Bacillus species recorded in this study can be recommended as potential bacteriocin starter cultures for the fermentation of microbiologically safe food products.