Characterization of Halotolerant Bacillus Species Isolated from Salt Samples Collected from Leather Factories in Turkey

Abstract

Salt curing is the method most commonly utilized in the leatherindustry to prevent microbial growth on raw hides/skins. Despitethis processing, a wide diversity of microorganisms belonging toDomains Bacteria and Archaea have nevertheless been observedon salted hides/skins. In order to understand whetherhalotolerant bacterial species in salt contaminate hides/skinsduring the curing process, 30 salt samples collected from 14leather factories in Corlu and Tuzla (Turkey) were examined forhalotolerant bacteria. Total counts of halotolerant bacterialnumbers, pH values and moisture contents of the salt sampleswere respectively determined between 104 CFU/g and 106 CFU/g,6.23 and 7.22, 0.90 and 5.02. All isolates were able to grow onboth Nutrient Agar Medium without NaCl and Nutrient Agaredium containing NaCl at concentrations ranging from 2 to10%. The microorganisms isolated from the samples wereidentified using phenotypic characteristics and comparativepartial 16S rRNA gene sequence analysis. The phylogeneticanalysis, using more than 1300 base comparisons of 16S rRNAsequence data, revealed 83 halotolerant isolates that share highlysimilar identities (97.82-100%) with their closest phylogeneticrelatives. These isolates were assigned to 12 different Bacillusspecies (B. amyloliquefaciens, B.atrophaeus, B.halotolerans, B.licheniformis, B.mojavensis, B.paralicheniformis, B.pumilus,B.safensis, B.siamensis, B.subtilis, B.tequilensis, B.velezensis). Wedetected catalase and protease activities, as well as productionacid from fructose, in all Bacillus isolates. Fifty-five isolatesdemonstrated positive oxidase activities, and 50 isolates utilizedcitrate as a sole carbon source. While a fairly high percentage ofthe isolates produced acid from maltose, almost half of theisolates produced acid from myo-inositol. While 67% of the saltsamples contained 1-2 different Bacillus species, 33% of the saltsamples contained 3-4 different Bacillus species. AlthoughB.amyloliquefaciens, B.atrophaeus, B.safensis, B.siamensisspecies were detected at a few salt samples, B.paralicheniformis and B.halotolerans species were detected at more than half of thesalt samples. These results uphold the hypothesis that proteolytichalotolerant Bacillus species in the curing salts may contaminatehides/skins during curing process. Hence, we recommendsterilized salts be used in the preservation of the hides/skins toprevent economic losses in the leather industry.