Highly selective acetate production from wine lees through acidogenic fermentation.

Area of Science:

• Biotechnology and Bioengineering
• Environmental Microbiology
• Sustainable Chemistry

Background:

• Winery wastes, specifically wine lees, possess untapped potential for carboxylic acid production.
• The high ethanol and low carbohydrate content in wine lees favors thermodynamically feasible ethanol oxidation to acetate.

Purpose of the Study:

• To assess the potential of wine lees for anaerobic acetate production.
• To evaluate the influence of different wine lees types (white and red) and co-fermentation conditions on carboxylate production.

Main Methods:

• Batch fermentation of white wine lees (WWL) and red wine lees (RWL) at 37°C and pH 5.5, with and without external inoculum.
• Co-fermentation of RWL with waste activated sludge at varying concentrations (20-100 gCOD/L).
• Microbial community analysis, focusing on hydrogen (H2)-producing and lactate-producing bacteria.

Main Results:

• Acetate was the predominant carboxylate (58-72% of COD) under tested conditions.
• Endogenous microbiomes in WWL performed similarly to external inoculums; however, RWL's endogenous microbiome showed limited carboxylate production, dominated by H2-producers.
• Co-fermentation at higher concentrations (70-100 gCOD/L) led to the appearance of caproate and heptanoate, with a microbiome enriched in lactate producers.

Conclusions:

• Wine lees are a promising substrate for anaerobic acetate production, with high selectivity observed.
• The endogenous microbiome's effectiveness varies depending on the wine lees type and its initial microbial community.
• The findings support the potential integration of wine lees fermentation into biorefinery processes for valuable chemical production.