Developments in high-throughput sequencing (HTS) technologies allow us to obtain large amounts of microbial information from wine and must samples. Thus approaches, that are aimed at characterising the microbial diversity during fermentation, can be enhanced, or possibly even replaced, with HTS-based metabarcoding. To reduce experimental biases and increase data reproducibility, we compared 3 DNA extraction methods by evaluating differences in the fungal diversity with Riesling alcoholic fermentation samples at four different vineyards. The fungal diversity profiling was done using the genetic markers ITS2 and D2 using metabarcoding. The extraction methods compared consisted of a commercial kit, a recently published protocol that includes a DNA enhancer, and a protocol based on a buffer containing common inhibitor removal reagents. All methods were able to distinguish vineyard effects on the fungal diversity, but the results differed quantitatively.
From the results of extraction methods, we applied the chosen methods and further combined the HTS tools of metabarcoding and metagenomics, to characterise how microbial communities of those samples, and their subsequent spontaneously fermented derivatives, vary. We specifically explored microbial community variation related to vineyard level, and during alcoholic fermentation. The vineyard was shown to be strongly influencing the microbial communities. Functional analyses were additionally included to investigate the microbial interactions. An increase in non-Saccharomycetaceae fungal functions and a decrease in bacterial functions were also observed during the early fermentation stage. Overall, our results highlight the importance of standardizing DNA extraction methods when characterising fungal diversity from wine and related samples, and showcase how metagenomic functional analysis offer possibilities to improve our insights into the wine alcoholic fermentation process, including highlighting microbe interactions.
Authors: Sarah Siu Tze Mak, Kimmo Sirén, Christian Carøe, Ulrich Fischer, M. Thomas P. Gilbert
Section for Evolutionary Genomics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
Institute for Viticulture and Oenology, Dienstleistungszentrum Ländlicher Raum Rheinpfalz, Neustadt an der Weinstraße, Germany
Keywords: Riesling, Metabarcoding, Metagenomics, DNA extraction