Heterologous production and characterization of a chlorogenic acid esterase from Ustilago maydis with a potential use in baking

• Functional production of Ustilago maydis chlorogenic acid esterase in Pichia pastoris.
• Distinguished from other chlorogenic acid esterases by its unique substrate profile.
• The enzyme preferred substrates typical of graminaceous monocots.
• Phenolic acids were released from complex side-streams of food processing.
• The enzyme effectively modified the rheological properties of wheat dough.

Ustilago maydis, an edible mushroom growing on maize (Zea mays), is consumed as the food delicacy huitlacoche in Mexico. A chlorogenic acid esterase from this basidiomycete was expressed in good yields cultivating the heterologous host Pichia pastoris on the 5 L bioreactor scale (reUmChlE; 45.9 U L−1). In contrast to previously described chlorogenic acid esterases, the reUmChlE was also active towards feruloylated saccharides. The enzyme preferred substrates with the ferulic acid esterified to the O-5 position of arabinose residues, typical of graminaceous monocots, over the O-2 position of arabinose or the O-6 position of galactose residues. Determination of kcat/Km showed that the reUmChlE hydrolyzed chlorogenic acid 18-fold more efficiently than methyl ferulate, p-coumarate or caffeate. Phenolic acids were released by reUmChlE from natural substrates, such as destarched wheat bran, sugar beet pectin and coffee pulp. Treatment of wheat dough using reUmChlE resulted in a noticeable softening indicating a potential application of the enzyme in bakery and confectionery.