BIOL 175-Botrytis cinerea effects on grape proteins: potential winemaking applications

Thaumatin-like (TL) proteins and chitinases are the predominant proteins in ripe grapes. Members of both groups are resistant to proteolysis and cause haze in wine if not removed before bottling. Currently, proteins are removed during winemaking using benotonite clay—a cumbersome and inefficient process. We seek to identify proteases that are capable of hydrolysing TL proteins and chitinases during winemaking. Several Aspergillus-based commercial protease mixtures are available for winemaking, but none eliminate the need for bentonite fining under winemaking conditions. Our group and others (Marchal et al 1998) have found that Botrytis cinerea infected grapes have significantly less protein than uninfected grapes. The lower protein concentrations in infected grapes may be caused by reduced expression of TL proteins and chitinases during grape development, by proteolytic enzymes from Botrytis, or by grape proteases. We will identify Botrytis and grape proteases in infected grapes by RT-PCR and mass spectrometry. In addition to identifying candidate proteases for overexpression in Pichia, we will characterize differences among Botrytis infected grapes and healthy grapes during grape development using proteomic tools such as peptide LC-MS/MS and isotope tagging.