Hpf2 Glycan Structure Is Critical for Protection against Protein Haze Formation in White Wine

Abstract

Grape-derived proteins can form haze in wine. Some cell-wall glycoproteins of Saccharomyces cerevisiae are capable of reducing protein haze formation. The basis of their haze protective activity is not yet understood. One of the S. cerevisiae cell-wall proteins, Hpf2, was produced in Pichia pastoris . An altered glycan structure in the P. pastoris -produced protein was associated with decreased solubility in water and reduced capacity to mitigate haze formation compared to native Hpf2 protein from S. cerevisiae. alpha-1,2-Linked mannose in the glycan chain was shown to be required for haze protective activity using a series of S. cerevisiae deletion mutants (mnn1-Delta, mnn2-Delta, mnn4-Delta, and mnn5-Delta), defective in different aspects of glycan processing. The effect of media additives phthalate, casamino acids, and yeast nitrogen base on Hpf2 production in P. pastoris were also evaluated. Casamino acids were shown to suppress Hpf2 production in P. pastoris .

Polysaccharide characterization of commercial dry yeast preparations and their effect on white and red wine composition

“…Other authors have showed that these compounds can also improve tartaric and/or protein stability because they inhibit tartrate salt crystallization (Moine-Ledoux & Dubourdieu, 2002) and/or reduce the protein haze in white wines (Dupin et al, 2000;Lomolino & Curioni, 2007;Moine-Ledoux & Dubourdieu, 1999;Schmidt et al, 2009).…”

Flocculation and transcriptional adaptation to fermentation conditions in a recombinant wine yeast strain defective for KNR4/SMI1

“…Since transcription of most cell wall biogenesis related genes is no longer required under stationary phase conditions, it is not surprising that most cell‐wall‐related categories enriched in the exponential growth sample are not relevant anymore for this sample point. Neither major structural cell‐wall mannoproteins nor mannoproteins that have been shown to contribute to wine stabilization3, 7 show significant overexpression of their cognate genes in EKD‐13 (perhaps with the exception of HPF2 , showing increased expression in the 10 g/L sample close but below the significance threshold used in this work). Our data would suggest an altered cell wall dynamics, due to relative changes in enzyme activities, rather than a generalized or specific increase of mannoprotein synthesis, as the main cause of mannoprotein release in the recombinant strain.…”

“…Even through aging on lees is performed to increase wine mannoproteins content, these compounds are released in appreciable amounts also during the fermentative steps in wine making. Increasing the amount of mannoproteins in wines contributes to improved tartaric stability,1, 2 stability against protein haze,3–11 aroma stability,12 foam properties of sparkling wines,13 or mouth feel and related characters 14. Mannoproteins also seem to stimulate growth of lactic‐acid bacteria in wine environments and thus the development of malolactic fermentation 15, 16.…”

Properties of Wine Polysaccharides

“…However, other authors have revealed that polysaccharides modulate the aggregation kinetics and final haziness, interfering with the aggregation process, but could not prevent it [87]. The ability of a yeast MP to stabilize wine proteins has been attributed specifically to the glycan portion of the proteoglycan [88]. Moreover, protein stabilization effectiveness in white wines has been related to MP chemical composition, concretely with their high mannose to glucose ratio [89].…”