A novel low-temperature-active pectin methylesterase from Penicillium chrysogenum F46 with high efficiency in fruit firming

• An acidic pectin methylesterase of family 8 was identified in P. chrysogenum F46.
• Recombinant gene product in P. pastoris had optimal activity at pH 5.0 and 40 °C.
• It was low-temperature active, remaining 52% of maximum activity even at 10 °C.
• Enzyme combination with calcium lactate significantly improved pineapple firmness.

A pectin methylesterase gene (pe8F46) was cloned from Penicillium chrysogenum F46 and successfully expressed in Pichia pastoris. The full-length cDNA consists of 969 bp and encodes a 322-residue polypeptide with the calculated molecular weight of 34.1 kDa. Deduced PE8F46 belongs to family 8 of carbohydrate esterases and shares 54% identity with a functionally characterised counterpart from Myceliophthora thermophile. Purified recombinant PE8F46 showed the optimal activity at pH 5.0 and 40 °C, and remained 52% maximum activity even at 10 °C. An orthogonal experiment was employed to determine the best conditions for firming pineapple dices. After incubation with 0.75% (w/v) PE8F46 and 0.4% calcium lactate (w/v) for 20 min, the firmness of pineapple dices was improved by 47.6%, 13.7% higher than that of a commercial pectinase complex. These results suggest that PE8F46 has application potential in the food industry.