ИСТИНА

During the last decades, bacteria, molds and yeasts have become more resistant towards classic antibiotics and synthetic biocidal compounds. Therefore, there is a need for new non-toxic biocides possessing a broad spectrum of antimicrobial activity and could, at least, reduce both the level of administration of classic antibiotics and potentially harmful synthetic biocides in the area of their application, i.e. food, pharmaceutical and personal care compositions. These products are susceptible to microbial contamination both during manufacturing in nonsterile conditions and during normal use by consumers so that preservatives are required to maintain quality and shelf-life of the products preventing the products from growth of pathogenic microorganisms, degradation and malodor. Unfortunately, safety of many synthetic preservatives are the subject of debate among regulators specializing in food chemistry, cosmetics and toxicology. In that respect, oligochitosan – an artificial polyaminosaccharide – is considered as a safe, biocompatible and biodegradable biopolymer possessing a broad range of antimicrobial activity against bacteria, molds and yeasts and potential candidate for practical applications in pharmaceutical, food and household products. Nevertheless, the application of oligochitosan is restricted in some formulations. The first restriction is that chitosan is insoluble in water but dissolves in acidic aqueous media, and its solubility and antimicrobial activity dramatically decreases as pH increases above critical pH (pHc) threshold point at~6.2-6.6. The second restriction for chitosan application in a series of products as a preservative is the interaction of positively charged in aqueous acidic media chitosan macromolecules with anionic surfactants (SDS), stabilizers, emulsifiers and thickening agents, whose are widely used in food, household and industrial cleaners, and personal care products, that leads to precipitation of a surfactant-polyelectrolyte complex (SPEC) from acidic aqueous media. As a result, insolubility of chitosan in alkaline solution and insolubility of chitosan-anionic additive complex make impossible or highly restrict the application of chitosan in the products. Recently, we have found that reacetylated chitosan (RA-CHI) having a random-type distribution of acetyl groups forms a transparent solution in the presence of SDS without SPEC formation and possesses a high antibacterial activity against Gram-positive and Gram-negative in both weakly acidic and weakly alkaline environments. Antibacterial activity and compatibility with SDS make RA-CHI promising for application of as an artificial antimicrobial agent in food, personal care and house-hold products containing liquid or semiliquid anionic surfactants.