Sequential combination of laccase pretreatment and acid extraction for high-yield pectin production from pomelo peels

A sequential combination of laccase pretreatment and acid extraction of pectin from pomelo peels was performed in this study. By using a laccase dose of 10 U/g, the yield and galacturonic acid content of the extracted pectin were 21.67% and 75.74%, respectively, which reflected an improvement by nearly 30% and 44% relative to the extraction process without laccase. Moreover, the degree of esterification of the extracted pectin was significantly improved as the laccase concentration was increased from 0 to 10 U/g but did not affect the molecular weight. Besides, the enzyme-treated sample displayed more than 29% loss of total lignin, in which the acid soluble lignin and the acid insoluble lignin were removed by over 15% and 33%, respectively. Scanning electron microscopy indicated that the penetration and partial destruction of the pomelo peel cell wall due to laccase might be one of the main reasons why laccase pretreatment could release pectin from cell wall complexes and increase the pectin yield in subsequent acid extraction processes.