EFFECT OF ALKALINE HYDROLYSIS FACTORS ON ANTI-BACTERIAL ACTIVITY OF SOLUBLE LIGNIN DERIVED FROM Annona Squmosa Linn PEEL

Abstract

This paper extracted the soluble lignin from dried Annona Squamosa Linn. peel and evaluated its antibacterial activity. The alkaline hydrolysis was used to break the insoluble-lignin structure to soluble lignin. To isolate the soluble lignin from hydrolysates, the pH adjustment method using concentrated H₂SO₄ was applied. The precipitated lignin was then weighted and evaluated antibacterial activity. Factors affecting the extraction eficiency of alkaline hydrolysis were investigated, including NaOH concentrations of 1.25; 2.5; 3.75, and 5 g/L, temperatures of 25, 50, 75, 105 ^oC and extract times of 60, 90, 120, and 150. The results showed that all tested parameters significantly impacted the weight of lignin and its antibacterial ability. The optimal condition was NaOH concentration of 2.5 g/L, temperature of 75 ^oC, extract time of 90 minutes. In that optimal condition, 0.76 g of precipitated lignin was obtained. The highest diameters of the zone of inhibition on Escherichia  coli and Salmonella typhi was 288 mm and 303 mm, equivalent to 87.3% and 94.7% compared to the positive control, respectively. These results showed that the dried Annona Squmosa Linn peel is a potential source for antibacterial chemicals.