Beverage spoilage yeast detection methods and control technologies: A review of Brettanomyces.

Spoilage yeasts detection is the key to improve the quality of alcoholic fermentation beverages such as wine and cider. The metabolic activity of the spoilage yeast causes irreparable damage to many liters of final products every year. Therefore, winemakers and cider-house companies suffer a substantial economic impact. Thus, over the years, many detection techniques have been proposed to control the occurrence of spoilage yeast. Out of the many spoilage yeast genera, Brettanomyces is one of the most commonly encountered in the beverage industry. Leveraging its ability to thrive in wine and cider conditions (low pH, high levels of ethanol, and low oxygenation levels), Brettanomyces can proliferate inside beverage production tanks. Moreover, their resultant by products reduce the quality of the beverage. While the beverage industry has made great strides in detecting harmful organisms, gaps remain. Traditional methods such as microscopy, cell plating, gas chromatography-mass spectrometry, etc. are often imprecise, expensive, and/or complicated. New emerging spoilage yeast detection platforms, such as biosensors and microfluidic devices, aim to alleviate these constraints. Novel platforms have already demonstrated great promise to be a real alternative for in situ and fast detection in the beverage industry. Finally, the review discusses the potential of emerging spoilage yeast detection and treatment methods.

Biomachining: Preservation of Acidithiobacillus ferrooxidans and treatment of the liquid residue.

Biomachining has become a promising alternative to micromachining metal pieces, as it is considered more environmentally friendly than their physical and chemical machining counterparts. In this research work, two strategies that contribute to the development of this innovative technology and could promote its industrial implementation were investigated: preservation of biomachining microorganisms (Acidithiobacillus ferrooxidans) for their further use, and making valuable use of the liquid residue obtained following the biomachining process. Regarding the preservation method, freeze-drying, freezing, and drying were tested to preserve biomachining bacteria, and the effect of different cryoprotectants, storage times, and temperatures was studied. Freezing at -80°C in Eppendorf cryovials using betaine as a cryoprotective agent reported the highest bacteria survival rate (40% of cell recovery) among the studied processes. The treatment of the liquid residue in two successive stages led to the precipitation of most of the total dissolved iron and divalent copper (99.9%). The by-products obtained (iron and copper hydroxide) could be reused in several industrial applications, thereby enhancing the environmentally friendly nature of the biomachining process.