Investigating the impact of non-Saccharomyces yeast on wine composition – Focus on extracellular enzymes of oenological interest


Project Number
IWBT-Y 11-01

Project title
Investigating the impact of non-Saccharomyces yeast on wine composition – focus on extracellular enzymes of enological interest

Project leader
Divol, B

Institution
University of Stellenbosch. Faculty of AgriSciences. Institute for Wine Biotechnology

Team members
Du Toit, M
Bauer, F F
Divol, B
Jolly, N P
Setati, E
Greyling, T

Project description
Over the past two decades, research has shown that certain non-Saccharomyces yeasts can be co-inoculated with S. cerevisiae in order to enhance the aromatic complexity of wines. Part of the contribution these non-Saccharomyces yeasts has been attributed to the secretion of extracellular enzymes (e.g. pectinases, glycosydases and proteases) that could break down certain grape compounds such as pectin, glycosylated aroma compounds and haze-forming proteins, respectively. In this study, a large collection of non-Saccharomyces yeasts was screened for these enzyme activities. The results show that pectinase activity is only found in Kluyveromyces marxianus. β-glucosidase activity was much more common and protease activity was the strongest in Metschnikowia pulcherrima and Zygoascus meyerae. Large strain variation was identified. The identification of extracellular proteins at the end of fermentation revealed that the main oenologically relevant enzymes present were glucanases and β-glucosidases. Novel protease genes from M. pulcherrima and Z. meyerase were retrieved. Their expression and the impact of their corresponding enzymes are currently under investigation in a follow-up project (IWBT W14/01). In conclusion, this study confirmed that non-Saccharomyces yeasts secrete a range of extracellular enzymes that could be of oenological interest. We also retrieved novel genetic genes encoding these enzymes. However, the actual secretion of these enzymes could only be partially confirmed under fermentative conditions and the actual activity and impact of these enzymes was not investigated. In future projects, we therefore propose to perform fermentations with pure and mixed yeast cultures and monitor the secretion and extracellular enzyme activity on wine substrates in order to confirm the relevance of these enzymes from an oenological perspective. In particular, the oenological potential of K. marxianus, M. pulcherrima and Z. meyerae should be investigated.

Poster(s)
Mostert, T T and Divol, B. 2014. Yeast co-inoculation and release of proteins: A proteomic approach. Poster presented at the 3rd Wine Active Compounds. 26-28 March 2014, Beaune, France.

Presentation(s)
Theron, L W, Zietsman, J J and Divol, B. 2013. Optimising recombinant expression and purification on an aspartic protease from Metschnikowia pulcherrima. Paper presented at the 19th South African Society for Microbiology Congress. 24-27 November, Warmbaths, South Africa.

Theron, L W, Zietsman, J J and Divol, B. 2013. Utilisation of acid protease produced by non-Saccharomyces yeast to prevent haze and release assimilable nitrogen. Paper presented the the 35th South African Society for Enology and Viticulture Conference. 13-15 November, Somerset West, South Africa.

Articles
Mostert, T T, Divol, B. 2012. Investigating the proteins released by yeasts in synthetic wine fermentations, International Journal of Food Microbiology, Mnth Nov (171C) (p. 108-118)
http://dx.doi.org/10.1016/j.ijfoodmicro.2013.11.010

Mostert TT, Divol B (2014) Investigating the yeast secretome in fermentation. International Journal of Food Microbiology 171, 108-118.

Reid, V J, Theron, L W, Du Toit, M, Divol, B. 2012. Identification and partial characterisation of extracellular aspartic protease genes from Metschnikowia pulcherriam IWBTY1123 and Candida apicola IWBT1384, Applied and Environmental Microbiology, Mnth Oct v. 78 (19) (p. 6838-6849)

Divol, B, Setati, E. 2015. Is die uitskeiding van hidrolitiese ensieme deur nie-Saccharomyces-giste ‘n belangrike eienskap vir wynmaak? WineLand, Mnth Oct (p. 78-80)
Article.pdf

Thesis
Mostert, T T. 2014. Investigating the secretome of non-Saccharomyces in model wine. MSc. University of Stellenbosch, Stellenbosch.

 

 

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