Production of D-galacturonic acid from pomelo peel using the crude enzyme from recombinant Trichoderma reesei expressing a heterologous exopolygalacturonase gene

D-galacturonic acid is a starting material for synthesizing biochemicals used in cosmetic, pharmaceutical, and fuel industries. Utilization of one-step enzymatic hydrolysis method for D-galacturonic acid production can reduce the use of toxic chemical and avoid high temperature in pectin extraction process. However, lack of efficient enzymes facilitating degradation of pectin-rich biomass into D-galacturonic acid limited an implementation of this process. In this study, a heterologous exoPG gene encoding exopolygalacturonase (exoPG), a key pectinase enzyme originating from Aspergillus aculeatus, was expressed in a well-known industrial cellulase-producing strain, Trichoderma reesei RUT-C30. Application of this crude enzyme in the pectin-rich pomelo peel hydrolysis at 60 °C, pH 6.0 for 48 h resulted in up to 151.1 mg/g D-galacturonic acid, which was approximately 6.1-fold higher than that obtained by the enzyme prepared from the parental strain. Further economic assessment of D-galacturonic acid production by using crude enzyme from the recombinant T. reesei revealed that the investment could be returned within 0.5–0.7 year, suggesting profitability of the developed process. The crude enzyme from the engineered T. reesei strain developed in this study promises a clean and sustainable production of D-galacturonic acid from low-cost agricultural waste.