Controlled release of allyl isothiocyanate for bacteria growth management

The ordered, mesoporous silica structures MCM-41 and SBA-15 were synthesized as potential vectors for the controlled release of allyl isothiocyanate. The average pore diameter of each silica was 2.45 ± 0.25 nm and 7.28 ± 0.50 nm, however the average pore volume across both samples was 0.817 ± 0.010 mL/g. The maximum loading was 95.3% and 93.9%; the wider pore size of SBA-15 ensured 80% of the available allyl isothiocyanate was released in the first 24 h whereas MCM-41 released approximately 1%/h up to 60 h. Antimicrobial tests were made against 8 microorganisms: Bacillus cereus, Listeria monocytogenes Staphylococcus aureus, Escherichia coli 25922, Salmonella Typhimurium, Vibrio parahaemolyticus, Pichia anomola and Schizosaccharomyce pombe. Controlled release and antibacterial activity from SBA-15 was always superior to those from MCM-41. Overall, allyl isothiocyanate released from the porous vectors was more efficient in controlling yeast and gram-negative bacteria than gram-positive bacteria. In comparison with evaporated liquid allyl isothiocyanate, no apparent loss of activity occurred as a consequence of adsorption and desorption processes in the pore network.