Antimicrobial activity of carbohydrate chitosan derivatives.

DÍAZ VERGARA LI; ARATA BADANO J; BRESER ML; PORPORATTO C; PEREYRA C; CAVAGLIERI L; MONTENEGRO MA

Mar del Plata

Congreso; XVI Simposio Latinoamericano de Polímeros (SLAP 2018) y el IV Congreso Iberoamericano de Polímeros (CIP 2018).; 2018

INTRODUCTIONChitosan (Ch) is a polysaccharide composed of β-(1→4)-N-acetyl-2-amino-2-deoxy-D-glucose and 2-amino-2-deoxy-D-glucose obtained from the alkaline deacetylation of chitin1. It is a natural, biocompatible, biodegradable, antioxidant, antimicrobial, non-toxic, mucoadhesive, antitumor compound2.Antimicrobial activity of Ch has been attributed to the molecular weight (MW) and the ?NH2 gropus3. However, this property is limited by the low solubility of Ch4. The modification with carbohydrates can improve the solubility5.The aims of this study were to evaluate the antimicrobial activity of different carbohydrate Ch derivatives against Staphylococcus aureus, Escherichia coli and Enterococcus faecalis.EXPERIMENTAL METHODSModification of Ch by Maillard ReactionCh derivatives were obtained by Maillard reaction. Briefly Ch 1% (w/v) was dissolved in 1% (v/v) CH3COOH and mixed with glucose or lactose 1% (w/v), the reaction mixture was kept in an orbital shaker for 4 h at 35 C (ChG) and 48 h or 60 h at 70 C (ChL48 and ChL60), respectively.Antibacterial activity. The antibacterial assays were performed according to standard CLSI methods for antimicrobial dilution susceptibility tests6. The minimum inhibitory concentration (MIC) values, expressed as % (w/v), against pathogenic Gram positive bacteria S. aureus ATCC 6538, S. aureus ATCC 29213, E. faecalis ATCC 29212, and Gram negative bacteria E. coli ATCC 35218, E. coli ATCC 81382, E. coli ATCC 81749 were evaluated.Flow CitometryViability evaluation and MIC were performed using the LIVE/DEAD BacLight Bacterial Viability Kit staining (ThermoFisher Scientific), according to the manufacturer?s instructions. Bacterial suspensions were acquired on an ACCURI C6 (BD Biosciences) flow cytometer and the data were analysed using FlowJo software (Tree Star).RESULTS AND DISCUSSIONDerivatives were previously characterized, obtained the following MW and deacetylation degrees DD (proportional to -NH2 groups), Ch (595 ± 89 kDa, 78.1%), ChG (278 kDa, 66.8%), ChLac48 (143 ± 63 kDa, 75.2%), ChLac60 (47 ± 7 kDa, 77.1%). The antimicrobial activity of the derivatives against Gram positive and negatives bacteria shows no changes, except for ChG that present a minor activity (Tables 1 and 2). This can be attributed to the diminution of ?NH2 groups in the ChG, while in ChLac48 and ChLac60 the increased time of reaction decreased the MW. Antimicrobial activity in Ch is determined by the ?NH2 groups and MW, an increase of ?NH2 groups increase the activity, on the contrary a decrease in the MW increase the activity1.CONCLUSIONThe derivatives with lactose presented a similar antimicrobial activity as native Ch, making them promising for their use in food and pharmaceutics products.