Treatment Using Both. Direct and Alternating Electric Currents on Hide Bacteria in Brine Curing and Pre-Soaking Liquors

Abstract

Animal hides support the growth of highly diverse Gram-negative and Gram-positive bacterial populations. These bacterial populations cause important damage to the hides during brine curing and pre-soaking processes, subsequently reducing the quality of the final leather. It is usually difficult to combat the diverse resistance offered by both Gram-negative and Gram-positive bacteria in these processes in a short time with conventional antimicrobials. Therefore, the present study examined the inactivation effect of a combined electric current treatment using both 1.5A direct and 2A alternating electric currents on: 1) each test isolate of Gram-negative bacteria (Enterobacter cloacae, Pseudomonas luteola, Vibrio fluvialis) and their mixed culture; 2) each test isolate of Gram-positive bacteria (Enterococcus faecium, Bacillus pumilus, Staphylococcus cohnii) and their mixed culture; 3) the mixed culture of test bacteria except for Gram-positive endospore-forming bacteria (Bacillus pumilus); 4) the mixed culture of all bacteria in liquid media containing organic substances and 25% NaCl. The test bacteria were isolated from salt-pack-cured hides. Two, three and four log reduction factors of all test bacteria were observed after the application of the direct electric current applied together with alternating electric current treatment for 12, 26 and 34 minutes, respectively. As a conclusion, the combined electric treatment applied for 34 minutes was found to be fairly effective in reducing the bacterial cell count to a relatively low level at which bacterial damage to the hides is reduced in brine curing and pre-soaking liquors.