Effect of chitosan as adsorben to bacto agar quality from Gelidium sp.

Abstract

Gelidium sp. is a seaweed that produces agar with a high gel strength. Bacto agar must have a high purity, so it needs a right purification method. One of the ways by adsorption process using chitosan. The aim of this research was to determine the influence of chitosan as an adsorbent and the optimum condition of its adsorption process. Bacto agar was extracted with water at 90°C. An alkali and acid pretreatment were added in the extraction process in order to increase thephysico-chemical properties of the agar gels. The agar extract was adsorbed by chitosan with various concentration of chitosan (0.5; 0.75; and 1%) and adsorption time (0, 30, and 60 minutes). The characteristic of bacto agar include moisture content, ash content, acid-insoluble ash content, sulphate content, gel strength, viscosity, syneresis, gelling and melting points, analysis of its molecular structure by FTIR and SEM. Bacto agar resulted in this research were tested as a bacterial culture medium using Total Plate Count (TPC) method. The best chitosan treatment process was obtained in bacto agar at 0,75% and 0 minute of adsorption which is had the physico-chemical properties that met the criteria of commercial bacto agar with 3.50% of bacto agar yield, 14.61% moisture content, 4.02% ash content, 0.93% acid-insoluble ash content, 1.34% sulphate content, 1054.96 g/cm² gel strength, 60 Cp viscosity, 4.62% syneresis, 65 °C and 20.75 °C of melting and gelling points respectively. The microbial analysis shows that bacto agar can be used as a bacterial culture medium.