A low-temperature polygalacturonase from P. occitanis: characterization and application in juice clarification

• Purification of a new polygalacturonase after one MonoQ-FPLC purification step. ≡ PG2 was optimally active at 35 °C and pH 6 with 85% of activity at pH7. ≡ DEPC strongly inhibited PG2 suggesting the implication of Histidine residue.
• Molecular analysis of the gene supported the presence of His residue.
• PG2 is more efficient on pear and banana than on citrus juice clarification.

An extracellular endo-polygalacturonase (PGase) was purified, after a single purification step, from the constitutive and hyperpectinolytic CT1 mutant of Penicillium occitanis. This enzyme named PG2 has a molecular weight of 42 kDa. It was optimally active at 35 °C and pH6 with more than 85% of activity at pH7 in contrast to the majority of fungal PGase, generally acting at 50 °C and pH5. The specific activity obtained was among the highest ones, 31397.26 U/mg. The PGase activity increased with the decrease of the degree of methylation (DM) of pectin, but it was also able to degrade the highly methyl-esterified substrates, 70% (DM) and 90% (DM), with almost 80% and 40% of residual activity respectively. Interestingly, PG2 is completely inhibited by DEPC, suggesting the implication of a Histidine residue in the active site. The sequencing of P. occitanis whole genome allowed us to identify the pga2 gene encoding PG2 and to localize the His residue, target of DEPC, while it was absent in the PG1 that resisted to DEPC. Besides that, the potentialities of PG2 have been put in use in juice clarification of pear, banana and citrus juice.