Study on the conversion of gellan into deacylated gellan

Abstract

Gellan, an exopolysaccharide, is produced by aerated and submerged fermentation using Sphingomonas paucimobilis bacteria strain. Gel made from gellan is characterised by variable properties which depend on the degree of acylation of gellan. Natural gellan (high acyl gellan) produces soft and elastic gel, whereas firm and crispy gel can be obtained from low acyl gellan. Depending on its characteristics, gellan can be used in either food processing or fruit preservation (e.g to produce preserving film). This study aims to produce deacylated gellan from natural gellan to increase the applicability of this product. Acyl component was cleaved from gellan by increasing the pH of fermentation medium to pH 10 using 2M NaOH. Reaction mixture was performed at 800C for 10 minutes and neutralized to pH 7 using 2M H2SO4. Deacylated gellan in aqueous solution was precipitated by 95% ethanol at a gellan solution/ethanol ratio of 1:2 (v/v). The recovery efficiency of deacylated gellan was 85.6%. The deacylated gellan was then dried, powdered, and packed in an Al/PE bag which can be stored at room temperature, but avoiding direct exposure to the sun light. Deacylated gellan was characterised by moisture content of 6.47%, ash content of 7.54%, pH of 7, gel strength of 437 g/cm2. This gellan product gave hard and crispy gel with the gel point temperature at 350C above.