Purification and characterization of an extracellular polygalacturonase from <i>Lactobacillus plantarum</i> strain BA 11

Abstract

Lactobacillus plantarum produced extracellular polygalacturonase in a medium containing 1.5% low methyl‐pectin (w/v) and 0.5% glucose (w/v) as inducers. The enzyme was purified (approximately 70‐fold) by ammonium sulphate fractionation, Sephadex G‐100 gel filtration and DEAE‐cellulose ion exchange chromatography. Two peaks (PG I and PG II) of enzymic activity were obtained from the DEAE‐cellulose column. The molecular mass of PG I was similar to that of PG II (32 000 Da). The K m values of PG I and PG II for sodium polypectate were calculated to be 1.63 mg/ml and 1.78 mg/ml respectively. Their isoelectric points were about pH 5.5. The pH optimum was 4.5, while the optimum temperature was 35°C for both PG I and PG II. The two purified enzymes had similar endo modes of action on polygalacturonic acid, as determined by comparison of viscosity reduction and reducing group release.