Yeast Multi-Enzymatic Systems for Improving Colour Extraction, Technological Parameters and Antioxidant Activity of Wine

Research background. Wine yeasts are a heterogeneous microbial group with high enzymatic potential that makes them a useful tool in winemaking. With a better understanding of their oenological properties, selection procedures can be optimised to obtain more efficient strains. The present study aimed to isolate and select yeasts from wine grape surface by studying their production of enzymes that hydrolyse plant cell wall polymers and by linking them to different technological parameters and antioxidant activity of wines. 
Experimental approach. Yeasts that were able to produce carbohydrolases and related enzymes of oenological importance were firstly selected on plates and subsequently identified. Then, a secondary selection of yeasts was carried out according to technological effects of their extracellular enzyme extracts on short macerations. In this way, the colour extraction, total polyphenol content, clarification, filterability and antioxidant activity were studied. This approach makes it possible to relate the microorganism capacity to produce cell wall depolymerizing-enzymes with the technological effects produced.
Results and conclusions. From 366 isolates, 26.2 % (96 strains) showed at least one of the polysaccharidase activities and 57.3 % (55 strains) of them exhibited a multi-enzyme blend active against plant cell wall polymers. Sixteen strains were selected and identified as Aureobasidium, Candida, Debaryomyces, Hanseniaspora, Metschnikowia, Pichia, Saccharomyces and Torulaspora. Pectinolytic enzymes displayed the highest hydrolytic activity levels. Aureobasidium pullulans showed a more comprehensive enzyme blend and higher activity levels, dominated by pectinases, and followed by xylanases and cellulases. Moreover, the Torulaspora delbrueckii m7-2 strain exhibited high polysaccharidase production levels and this was strain-dependent. Strains that produced the most comprehensive enzyme extracts and the highest levels of activity also exhibited the best chromatic and technological properties. Cluster analysis confirmed that A. pullulans R-22, m11-2, m86-1 and m86-2 and T. delbrueckii m7-2 could be grouped for a better effect on filterability, clarification and extraction of bioactive compounds, encouraging future studies regarding their application in winemaking. 
Novelty and scientific contribution. The study of yeast multi-enzymatic systems impacting in the grape maceration process results in a proper selection criterion for wine yeasts to improve colour extraction, technological parameters and antioxidant activity of Malbec wine. This work shows that A. pullulans and T. delbruekii have high enzymatic potential for oenological purposes.