Safety assessment of surfactin-producing Bacillus strains and their lipopeptides extracts in vitro and in vivo

Abstract

Beneficial Bacillus strains can be administered to livestock as probiotics to improve animal health. Cyclic lipopeptides produced by Bacillus such as surfactins may be responsible for some of the beneficial effects due to their anti-inflammatory and immunomodulatory activity. The aim of the present study was to isolate and evaluate the biocompatibility of native Bacillus spp. strains and their surfactin-like lipopeptides in vitro and in vivo to determine their potential to be used on animals. Biocompatibility of endospore suspensions (108 UFC/ml), and different dilutions (1:10; 1:50; 1:100; 1:500 and 1:1000) of Bacillus lipopeptide extracts containing surfactin was tested on Caco-2 cells by a MTT-based colorimetric assay. Genotoxicity was tested on BALB/c mice (n=6) administered 0.2 ml of endospore suspensions by the bone marrow erythrocyte micronuclei assay. All the isolates tested produced between 26.96 and 239.97 µg ml-1 of surfactin. The lipopeptide extract (LPE) from isolate MFF1.11 was the only that demonstrated significant cytotoxicity in vitro. In contrast, LPE from MFF 2.2; MFF 2.7, TL1.11, TL 2.5 and TC12 had no effect on the viability (V%> 70%) of Caco-2 cells. Similarly, none of the endospore suspensions affected cell viability (V%>80%). Likewise, endospores did not cause genotoxicity on BALB/c mice. This study was elementary as a first step for a new line of research, since it allowed us to choose the safest isolates to keep working on the search of new potentially probiotic strains destined to improve health and performance of production animals.