Study of polygalacturonase production by an Antarctic yeast and obtention of dragon fruit juice by maceration at mild temperature

The objectives of the present survey were to study the production and the biochemical characterization of an enzymatic cold-active extract with polygalacturonase activity, to perform a first insight into its possible application in fruit-juice obtention process, and to use this juice for food products preparation. The enzymatic extract was produced by the Antarctic yeast Mrakia sp. LP January 7, 2016 in a bioreactor with citric pectin as substrate. The polygalacturonase activity showed optimum conditions for reaction at 45 °C and pH 5.0. This activity was stable until 40 °C but deactivated at higher temperatures. Inhibition by Hg+2 suggested the presence of a thiol-dependent enzyme. A high-molecular polygalacturonase was detected in an SDS-PAGE and zymography analysis. Reaction-products were observed by thin-layer chromatography and suggested the endo-mode of action. The enzymatic extract had some accessory enzymes, such as pectin methylesterase, β-glucosidase, cellulase and inulinase. As a first insight into the potential use of this enzymatic extract for fruit maceration at mild temperatures, red and white dragon fruits were selected as models. At 23 °C, juice yields of 15%–23% higher than control were obtained after treatments, with a decrease of remanent solid of 25%–35%. The color of red dragon fruit juice increased with enzymatic treatment. Alginate balls that were prepared with the juices demonstrated a hardness of ∼10 N. The compression force of low-calorie sugar gels was 3.8 N. This work provided a complete study of the production, characterization, application and food product production using a new cold-active polygalacturonase extract of Antarctic origin.