Evaluation and characterization of some protective culture metabolites in free and nano-chitosan-loaded forms against common contaminants of Egyptian cheese.

•This study aims to evaluate the contribution of chitosan nanoparticles to enhance the antimicrobial activity.•Nisin and Natamycin will be applied either in the free-state or loaded on chitosan nanoparticles.•Disc diffusion assay, Lb. helveticus crude CFS recorded the highest potency against all bacterial indicators.•The recorded MIC values were found to be higher in case of tested bacteria than yeast and fungus.•CFS with HS–GC–MS showed that Lb. helveticus produces a wide range of antimicrobial& health-promoting substances.