Genomic insights into Staphylococcus equorum KS1039 as a potential starter culture for the fermentation of high-salt foods

Abstract

BackgroundOur previous comparative genomic analysis of Staphylococcus equorum KS1039 with five S. equorum strains illuminated the genomic basis of its safety and salt tolerance. However, a comprehensive picture of the cellular components and metabolic pathways involved in the degradation of macromolecules and development of sensory properties has not been obtained for S. equorum. Therefore, in this study, we examined the general metabolism of S. equorum based on information obtained from published complete genome sequences of six S. equorum strains isolated from different niches. Additionally, the utility of strain KS1039 as a starter culture for high-salt food fermentations was examined.ResultsAll six S. equorum strains contained genes involved in glycolysis, the tricarboxylic acid cycle, and amino acid metabolic pathways, as well as color development. Moreover, the strains had the potential to produce acetoin, butanediol, and branched chain fatty acids, all of which are important flavor compounds. None of the strains contained decarboxylase genes, which are required for histamine and tyramine production. Strain KS1039 contained bacteriocin and CRISPR/Cas gene clusters, and experimental results suggested that these genes were functional in vitro.ConclusionsThe comparative genomic analysis carried out herein provides important information on the usefulness of S. equorum KS1039 as a starter culture for the fermentation of high-salt foods in terms of safety, salt tolerance, bacteriocin production, and foreign plasmid restriction.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4532-1) contains supplementary material, which is available to authorized users.

Nonconventional starter cultures of coagulase-negative staphylococci to produce animal-derived fermented foods, a SWOT analysis

“…Strains of S. equorum , for instance, are equipped with a substantial proteolytic system (Lee et al . ). Yet, proteolytic activity is strain dependent (Casaburi et al .…”

“…; Lee et al . ). Also, the capacity to produce lactic acid, acetic acid, diacetyl and acetoin is common (Beck et al .…”

“…; Lee et al . ). Yet, their degree of production depends on both the strain used and the conditions applied, for instance with respect to oxygen availability (Sánchez Mainar et al .…”

“…; Lee et al . ). Staphylococcus succinus and S. vitulinus are of interest too, already being commercialized for cheese (Sacco System) and for cheese and meat (Danisco; http://www.danisco.com/food-beverages) respectively.…”

“…Yet, for nonpathogenic CNS, focus has been on metabolic traits of technological interest rather than on ecological aspects (Fadda et al 2002;Madsen et al 2002;Casaburi et al 2008). Genome-based analyses has further shed light on these issues by confirming prior insights or revealing new characteristics (Rosenstein et al 2009;Lee et al 2018). As a first metabolic asset, CNS species display proteolytic and lipolytic activities (Casaburi et al 2008;M€ uller et al 2016a), although during food fermentations these activities are predominantly ascribed to endogenous rather than staphylococcal enzymes (in meat and fish; Flores and Olivares 2014;Sriket 2014) or to rennet and the lactic acid bacteria (LAB) microbiota (in cheese; Zhao et al 2016).…”