Inactivation of Escherichia coli O157:H7 and Salmonella spp. on alfalfa seeds by caprylic acid and monocaprylin

Alfalfa and other seed sprouts have been implicated in several Escherichia coli O157:H7 and Salmonella spp. human illness outbreaks in the U.S. Continuing food safety issues with alfalfa seeds necessitate the need for discovery and use of novel and effective antimicrobials. The potential use of caprylic acid (CA) and monocaprylin (MC) for reducing E. coli O157:H7 and Salmonella spp. populations on alfalfa seeds was evaluated. The effectiveness of three concentrations of CA and MC (25, 50, and 75 mM) to reduce E. coli O157:H7 and Salmonella spp. populations in 0.1% peptone water and on alfalfa seeds was evaluated. Surviving populations of E. coli O157:H7 and Salmonella spp. were enumerated by direct plating on tryptic soy agar (TSA). Non-inoculated alfalfa seeds were soaked for up to 120 min to evaluate the effect of CA and MC solutions on seed germination rate. For planktonic cells, the efficacy of the treatments was: 75 MC > 50 MC > 25 MC > 75 CA > 50 CA > 25 CA. Both E. coli O157:H7 and Salmonella spp. were reduced to below the detection limit (0.6 log CFU/ml) within 10 min of exposure to 75 MC from initial populations of 7.65 ± 0.10 log CFU/ml and 7.71 ± 0.11 log CFU/ml, respectively. Maximum reductions of 1.56 ± 0.25 and 2.56 ± 0.17 log CFU/g for E. coli O157:H7 and Salmonella spp., respectively, were achieved on inoculated alfalfa seeds (from initial populations of 4.74 ± 0.62 log CFU/g and 5.27 ± 0.20 log CFU/g, respectively) when treated with 75 MC for 90 min. Germination rates of CA or MC treated seeds ranged from 84% to 99%. The germination rates of CA or MC soaked seeds and water soaked seeds (control) were similar (P > 0.05) for soaking times of ≤ 90 min. Monocaprylin (75 mM) can be used to reduce E. coli O157:H7 and Salmonella spp. on alfalfa seeds without compromising seed viability.     

Antifungal and antibacterial effects of 1‐monocaprylin on textile materials

The efficacy of a new antimicrobial treatment of textile materials based on the use of 1‐monocaprylin against various species of saprophytic moulds (Alternaria alternate CCM F‐397, Aspergillus niger ATCC 16404, Mucor racemosus CCM 8190, Penicillium ochrochloron CCM F‐158, Trichoderma viridae CCM F‐728), pathogenic moulds (Epidermophyton floccosum CCM 8339, Trichophyton mentagrophytes ATCC 9533, Trichophyton rubrum DSMZ 4167), pathogenic yeasts (Candida albicans ATCC 10231, Candida parapsilosis CCM 8260), Gram‐negative bacteria (Escherichia coli ATCC 11229, Klebsiella pneumoniae ATCC 4352) and Gram‐positive bacteria (Staphylococcus aureus ATCC 6853) was investigated. The testing was carried out according to DIN EN ISO 20645 disc‐diffusions test, using a 2‐layer method. The results showed that 1‐monocaprylin effectively killed all tested bacterial strains and pathogenic microorganisms with an exception of saprophytic moulds only, which were partially resistant. Textiles treated with 1‐monocaprylin reduced the growth of pathogenic, potentially dangerous microorganisms frequently occurring for example on the feet and in the shoes. Practical applications: To prevent microbial contamination leading to degradation of textile materials, various antimicrobial agents aimed at killing or suppressing of microorganism growth are applied. Among others, also MAGs belong to safe and efficient antimicrobial agents. Their application in antimicrobial treatment of textiles may be a suitable alternative to commercially used antimicrobial agents, as these endogenous lipid substances are present almost in all animal and plant tissues and are harmless to human body. The present study has confirmed that MAGs possess a suitable inhibitory activity when applied on textiles and are capable of hindering and even suppressing growth of bacteria and moulds that may occur during storage and use of textiles. The obtained results can be closely related to potential industrial applications of MAGs as effective agents for antimicrobial textiles and lining and insole materials for footwear, including those designed for diabetics.     

Mesoporous materials as host for an entrapped enzyme

Three mesoporous materials, silica, alumina and titania, were used as host for a lipase and the enzyme-loaded particles were employed as catalyst for esterification of caprylic acid using a mixture of glycerol and water as reaction medium. The reaction proceeded well with all three oxides but alumina gave considerably higher conversion than the other two. Hydrophobized silica gave an even higher degree of esterification. The degree of esterification obtained is believed to depend on the microenvironment of the enzyme. When alumina, which is positively charged under the conditions used, and hydrophobized silica are used as host material, the negatively charged lipase can be assumed to be adsorbed at the walls of the pores. The water activity is believed to be lower at the solid surface than in the middle of the pores, where the enzyme is situated when silica and alumina are used as host material. It is shown that the lipase is not irreversibly entrapped in the pores of the mesoporous materials. When the particles are removed by filtration after completed reaction and subsequently washed with an aqueous buffer, the enzyme is leached out. The lipase can be immobilized in the pores, however, by cross-linking in situ inside the pores using glutaraldehyde as cross-linking agent. Mesoporous materials loaded with cross-linked lipase can be reused several times with only marginal loss of activity.