_applied sciences_  
_Article_  
**Examination of the Bactericidal and Fungicidal Activity of**  
_Bacillus amyloidosisefaciens_ **M Isolated from Spring Waters**  
in Bulgaria  
**[PERSON] 1, [PERSON] 1 (c), [PERSON] 2,*, [PERSON] 2, [PERSON] 1 and [PERSON] 3(c)**  
1 Department of Microbiology, University of Food Technologies, 26 Maritza Boulevard, 4002 Plovdiv, Bulgaria; [EMAIL_ADDRESS] (B.G. ); [EMAIL_ADDRESS] (Y.G. ); [EMAIL_ADDRESS] (Z.D.) 2 Department of Biochemistry and Molecular Biology, University of Food Technologies, 26 Maritza Boulevard, 4002 Plovdiv, Bulgaria; [EMAIL_ADDRESS]  
3 Department of Wine and Beer Technology, University of Food Technologies, 26 Maritza Boulevard, 4002 Plovdiv, Bulgaria; [EMAIL_ADDRESS]  
* Correspondence: [EMAIL_ADDRESS]  
**Abstract** In order for a strain to be considered a probiotictic or suitable plant bioprotective agent, it must have proven antimicrobial activity against pathogenic bacteria and phytopathogenic fungi:  
_Bacillus amyloidefaciens_ M exhibited significantly high antifungal activity against pathogenic fungi of the genera _Aspergillus_, _Penicillium_, _Fusarium_, and _Sclerotinia_; yeasts of the genera _Candidia_ and _Saccharomyces_; as well as high antibacterial activity against pathogens of the genera _Escherichia_, _Salmonella_, _Staphylococcus_, _Listeria_, _Pseudomonas_, and _Bacillus_. The manifested antimicrobial activity was influenced by the composition of the growth medium. The antifungal activity of the strain was investigated at growth temperatures of 30 \({}^{\circ}\)C and 37 \({}^{\circ}\)C, and at different pH values in aerobic and anaerobic cultivation, under static and dynamic culturing conditions. High antifungal activity was observed at the 24 th h on both growth media (LBG broth and MPB broth) at pH = 6 and pH = 7 in aerobic and anaerobic cultivation. _Bacillus amyloidefaciens_ M produced antibiotic substances at pH > 5.0, and the antibiotic substances were either secreted into the medium or associated with the cell surface. Four compounds with different antifungal activity and different R\({}_{\rm f}\) values were registered through thin-layer chromatography (R\({}_{\rm f1}\) = 0.47; R\({}_{\rm f2}\) = 0.55; R\({}_{\rm f3}\) = 0.67; and R\({}_{\rm f4}\) = 0.75), two of the compounds were ninhydrin-positive. _Bacillus amyloidefaciens_ M was cultured in a bioreactor with stirring, and the parameters of the growth kinetics and the sporulation kinetics have been modeled. A spore concentrate of _Bacillus amyloidefaciens_ M has been obtained. In further research, the efficiency of the concentrate as a plant bioactive agent will be tested. _Sclerotinia sclerotium_ var _scleroria_; _Bacillus amyloidefaciens_; antibiotics; biosurfactants; bactericidal activity; antifungal activity  
**1. Introduction**  
Antibiotics are administered to control the growth and spread of pathogenic microorganisms in the gastrointestinal tract, as well as for good digestion and absorption and metabolism of nutrients [1, 2]. This is of particular importance for animal husbandry, since antibiotics applied to accelerate growth have a positive effect. Regardless of the positive effect of the applied antibiotics, their widespread use has led to new problems for humans, plants, and animals because of the occurrence of cross- and multi-antibiotic resistance and dysbacteriosis [3, 4]. This necessitated the use of other natural products as an alternative to antibiotics. Probiotics, plant extracts, essential oils, antimicrobial peptides, acidifiers, and enzymes fall within this definition [5]. These agents can be applied either alone or, more often, in combinations [6]. According to FAO/WHO 2002 [7], probiotics are defined as follows: \"Non-pathogenic bacteria for humans, possessing antagonistic activity towards pathogenic and opportunistic bacteria and ensuring the restoration of normal microflora\".