Location: Plant Gene Expression Center
Project Number: 2030-12210-003-013-A
Project Type: Cooperative Agreement
Start Date: Jul 15, 2025
End Date: Jul 14, 2026
Objective:
1. Identify and characterize native grape microbiota capable of metabolizing a broad spectrum of smoke-derived compounds (i.e. volatile phenols – VP)
2. Evaluate microbial interactions and functional performance in mixed cultures and model grape matrices.
3. Assess the resilience and functional activity of native VP-degrading microbes under winemaking-relevant conditions
Approach:
The cooperator agrees to work closely with ARS in planning and conducting the research outlined below. In particular, we would like to have monthly smoke taint meetings to organize and conduct research that best utilizes the team's areas of expertise. Initial work has previously isolated microorganisms that can metabolize guaiacol as a primary carbon source. This project will continue the effort to isolate native microbes from grape berries and the vineyard environment that can metabolize a variety of VPs. Both existing and novel isolates will be screened for catabolic activity against individual smoke marker compounds (e.g., o-, m-, and p-cresol; syringol; 4-methylsyringol). Isolates with VP biotransformation activity will be characterized using metabolite profiles and their possible degradation pathways examined. If genome sequences are available, molecular tools will be used to identify potential functional traits and catabolic mechanisms involved in VP degradation. The main goal of objective #2 is to assign functional groups of VP degraders so that they might be combined into a consortium that could degrade multiple VPs in grape must and wine. First, we will test microbial survival and compound degradation in synthetic grape matrices that simulate key features of grape must (e.g., high sugar, polyphenols, organic acids). We will monitor population dynamics, VP degradation efficiency, and any interactions among strains. Once characterized, functionally distinct microbes will be combined and evaluated in defined microbial consortia to assess compatibility and VP degradation using minimal and complex media. Finally, we will study optimal culture conditions (e.g., nutrient balance, inoculation ratios) that support synergistic VP biotransformation by any identified consortium. First, we will conduct assays under both static and aerated conditions to understand redox relevant growth conditions. We will evaluate microbial viability and VP-degrading activity across a range of enological conditions, including wine-relevant pH (3.0–3.8), SO2 concentrations, ethanol levels, and redox states. Depending on the growth and VP degradation optima defined, this activity could be incorporated into the winemaking process as a pre-fermentation step. Finally, we will investigate potential interventions to support microbial performance (e.g., oxygenation regimes, micronutrient supplementation, immobilization techniques), again as a practical addition to a fermentation scheme. We will measure residual VP concentrations in treated versus control matrices to assess which aspects have the greatest impact.