2008 S3: Emily Henk

Identifying lactic acid bacteria in Michigan cherry wines

Many factors contribute to the final flavor of wine. One factor is malolactic fermentation, during which lactic acid bacteria (LAB) transform the harsh tasting malic acid into a more drinkable lactic acid in grape wine. The role of LAB in the production of cherry wine is completely unknown. The goal is to identify the species of LAB in cherry wine and compare them to those found in grape wines. Bacteria from cherry wine were grown on general media plates and plates fortified with malic acid, which may provide optimal growing conditions for the LAB. To identify the bacteria, we will isolate 16S ribosomal DNA sequences, which encode a general gene found in all bacteria. We will then narrow our focus to a specific variable region of the gene; this will differentiate the DNA of different LAB after sequencing. To isolate the 16S gene and the variable regions, we will use polymerase chain reactions (PCR) which will exponentially copy the desired region of DNA. The PCR products will go through submarine gel electrophoresis to confirm the size of the 16S sequences and the specific variable region. We will sequence the variable region PCR products and the DNA sequences will be entered into an online database which will allow us to identify the bacteria. By identifying LAB in cherry wine, winemakers may be able to determine how to use LAB to enhance the final flavor of wine and discourage growth that contributes to spoilage of wine.

Faculty Mentor: Margaret Dietrich, Biology