Monitoring Site-Specific Fermentation Outcomes via Oxidation Reduction Potential and UV-Vis Spectroscopy to Characterize "Hidden" Parameters of Pinot Noir Wine Fermentations

Characterization of 20 Oenological Tannins from Different Botanical Origins for Formulation of Blends with Redox Potential Tuning Ability in Model Wine Solution

Twenty oenotannins from different botanical origins were studied in model wine solution (1 g/L, 12% ethanol, pH 3.5). An original device was created for measuring Oxidation-Reduction potential (ORp) of the solutions at 20 °C in strict anoxic condition by the electrochemical method of the platinum electrode zero-current potential. Reactivity against proteins and antioxidant properties were related to the chemical structure and, consequently, to the botanical origin of the oenotannins. The highest turbidity after BSA addition (ΔNTU > 1000) values were measured for the gallic hydrolysable tannins. The ORp versus standard hydrogen electrode ranged from 420 to 260 mV. The ellagitannins had the highest antioxidant power (AP%), followed by condensed tannins and gallotannins, highlighting a correlation with the phenolic profile. Based on these findings, two formulations were prepared as a blend of some of the tested oenotannins, with the ability to increase (MIX1) and decrease (MIX2) the ORp of the model wine.

Advanced Monitoring and Control of Redox Potential in Wine Fermentation across Scales

Combined with real-time monitoring of density and temperature, the control of the redox potential provides a new approach to influencing cell metabolism during growth, cell viability and non-growing yeast activity in wine fermentations. Prior research indicates that the problem of sluggish and incomplete fermentation can be alleviated by maintaining a constant redox potential during the ethanol fermentation. A secondary trait of hydrogen sulfide formation from elemental sulfur also seems to be associated with the development of low redox potentials during fermentation and this might be prevented by the deliberate control of redox potentials in a certain range. While the control of the redox potential during wine fermentations has been demonstrated previously at the research scale (100 L), the ability to control it in larger volumes typically seen in commercial conditions remained unanswered. Wine fermentations from the same load of Cabernet Sauvignon grapes from the 2021 harvest were conducted at three volumes: 100 L and 1500 L in a research winery and 10,000 L in a commercial winery. Using only pulses of air delivery, the redox potential was successfully controlled to −40 mV referenced to a silver/silver chloride electrode throughout the fermentations, at all scales. This appears to be the first published result of a controlled fermentation trial that includes the commercial scale and demonstrates the scalability of control of redox potential in wine fermentations.

A sustainable and effective bioprocessing approach for improvement of acid phosphatase production and rock phosphate solubilization by Bacillus haynesii strain ACP1

There is indeed a tremendous increase in biotechnological production on a global scale, more and more innovative bioprocesses, therefore, require to perform ideally not only in a small lab- but also on large production scales. Efficient microbial process optimization is a significant challenge when accomplishing a variety of sustainable development and bioengineering application objectives. In Egypt's mines, several distinct types of rock phosphate (RP) are utilized as a source of phosphate fertilizers in agriculture. It is more ecologically beneficial to utilize RP bio-solubilization than acidulation. Therefore, this work aimed to strategically scale up the acid phosphatase (ACP) production and RP bio-solubilization by the newly-discovered Bacillus haynesii. The use of consecutive statistical experimental approaches of Plackett-Burman Design (PBD), and Rotatable Central Composite Design (RCCD), followed by pH-uncontrolled cultivation conditions in a 7 L bench-top bioreactor revealed an innovative medium formulation. These approaches substantially improved ACP production, reaching 207.6 U L^-1 with an ACP yield coefficient Y_p/x of 25.2 and a specific growth rate (µ) of 0.07 h^-1. The metals Na, Li, and Mn were the most efficiently released from RP during the solubilization process by B. haynesii. The uncontrolled pH culture condition is the most suitable setting for simultaneously improving the ACP and organic acids production. The most abundant organic acid produced through the cultivation process was lactic acid, followed by glutamic acid and hydroxybenzoic acid isomer. The findings of TGA, DSC, SEM, EDS, FTIR, and XRD analysis emphasize the significant influence of organic acids and ACP activity on the solubilization of RP particles.