The Use of Hanseniaspora occidentalis in a Sequential Must Inoculation to Reduce the Malic Acid Content of Wine
, Stefano Scansani 1, Beata Beisert 1, Silvia Brezina 1, Stefanie Fritsch 1, Heike Semmler 1, Isak S. Pretorius 2, Doris Rauhut 1 and Christian von Wallbrunn 1,*
Round 1
Reviewer 1 Report
In this work, the authors describe the utilization of the yeast Hanseniaspora occidentalis in the fermentation of grape must, in co-culture with S. cerevisiae. Overall the manuscript presents interesting data, in particular the ability of H. occidentalis to consume the malic acid present in the must. This yeast was also able to consume higher levels of malic acid added to the same must. The manuscript is well written, and the data is clearly presented.
Some minor corrections and suggestions
Introduction
The authors could add some information on H. occidentalis in the introduction section since it is only mentioned that this yeast is found in vitivinicultural settings
Materials and Methods
Line 64 – please include the collection number of the H. occidentalis strain.
Line 89- Please clarify to the reader why no airlocks were used in fermentation when using only H. occidentalis
Line 92- The initial and final parts of this sentence are the same.
Line 97- To clarify this sentence replace “ in addition” with “The HPLC analysis was done with a …
Results and discussion
Line 194- The authors could state some examples of the levels of malic acid in some of these fruit musts.
Line 205- Did the authors search for homologs to known malate transporters and malic acid enzymes in the H. occidentalis genomes? It could be interesting to discuss this data here as well.
Author Response
Please see attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper addresses an issue of practical interest to the wine production sector, concerning the use of Hanseniaspora occidentalis to reduce the malic acid content in wines in a sequential must inoculation with Saccharomyces cerevisiae.
The main contribution of the work results from coming across with a Hanseniaspora strain showing the capacity to degrade malic acid.
I would like to see the authors clarifying the following aspects:
· Despite Hanseniaspora uvarum and H. guilliermondii are two of the most relevant Hanseniaspora species in grape must and wine, they are not mentioned in the introduction of the manuscript. Why?
· How was the Muscaris grape must pasteurized (Temp/Time)?
· What was the initial concentration of H. occidentalis in the fermentations?
· Why testing 17.1 and 14,4 g/L of malic acid? This is well above the maximum concentration levels tipically found in wine.
· Discuss deeper the differences between the proposed method to reduce malic acid (using H. occidentalis) and the most popular biological deacidification method of wines - the malolactic fermentation - in the quality and final composition of wines.
Author Response
Please see attachment
Author Response File: Author Response.pdf
