Machine Learning Techniques Disclose the Combined Effect of Fermentation Conditions on Yeast Mixed-Culture Dynamics and Wine Quality

The use of yeast starter cultures consisting of a blend of Saccharomyces cerevisiae and non-Saccharomyces yeasts has increased in recent years as a mean to address consumers’ demands for diversified wines. However, this strategy is currently limited by the lack of a comprehensive knowledge regarding the factors that determine the balance between the yeast-yeast interactions and their responses triggered in complex environments. Our previous studies demonstrated that the strain Hanseniaspora guilliermondii UTAD222 has potential to be used as an adjunct of S. cerevisiae in the wine industry due to its positive impact on the fruity and floral character of wines. To rationalize the use of this yeast consortium, this study aims to understand the influence of production factors such as sugar and nitrogen levels, fermentation temperature, and the level of co-inoculation of H. guilliermondii UTAD222 in shaping fermentation and wine composition. For that purpose, a Central Composite experimental Design was applied to investigate the combined effects of the four factors on fermentation parameters and metabolites produced. The patterns of variation of the response variables were analyzed using machine learning methods, to describe their clustered behavior and model the evolution of each cluster depending on the experimental conditions. The innovative data analysis methodology adopted goes beyond the traditional univariate approach, being able to incorporate the modularity, heterogeneity, and hierarchy inherent to metabolic systems. In this line, this study provides preliminary data and insights, enabling the development of innovative strategies to increase the aromatic and fermentative potential of H. guilliermondii UTAD222 by modulating temperature and the availability of nitrogen and/or sugars in the medium. Furthermore, the strategy followed gathered knowledge to guide the rational development of mixed blends that can be used to obtain a particular wine style, as a function of fermentation conditions.

Study of the Yeast Strain Influence and the Alcoholic Fermentation Conditions on the Higher Alcohols and Aldehydes Content in Gamza Wines

The influence of temperature and inoculum amount of yeast culture on the ability of the strains Saccharomyces cerevisiae Badachoni and Saccharomyces cerevisiae 24-6 to synthesize higher alcohols and aldehydes was studied. Yeast showed the highest fermentation activity at a temperature of 28oC. Neural networks had been applied and mathematical models were derived, describing with high accuracy the experimental data on the change of the total amount of higher alcohols and aldehydes in the fermentation process depending on the conditions. The higher alcohols ratio had increased during the process. The Badachoni strain revealed better ability to synthesize the studied metabolite as compared to the 24-6 strain. The Badachoni had produced the greatest amount of higher alcohols when the process occurred at 28°C, whereas the 24-6 at 24oC. The aldehydes synthesis had reached its peak during the rapid fermentation, thereafter it began to go down. The studied yeast synthesized more aldehydes when the process took place at a lower temperature. For both strains the maximum was observed under the conditions 20oС/4%. The analysis of the obtained wines had confirmed that quantitatively Badachoni produced more total higher alcohols and the 24-6 more total aldehydes. In both strains within one temperature range, in all variants, with increasing the inoculum amount of yeast culture the studied metabolites ratio went up too.

Screening and Identification of Yeasts from Fruits and Their Coculture for Cider Production

Coculturing non-Saccharomyces yeasts with Saccharomyces cerevisiae could enrich the aromatic complexity of alcoholic beverages during cider brewing. Therefore, the present study performed rapid strain screening via selective culture medium and aroma analysis and adopted a response surface methodology to optimize fermentation conditions to produce 2-phenylethyl acetate (PEA), which presents a rose and honey scent. The effects of coculturing yeasts on cider quality were evaluated through hedonic sensory analysis and the check-all-that-apply (CATA) method. Hanseniaspora vineae P5 and S. cerevisiae P1 produced ciders with high levels of PEA and 2-phenylethanol, respectively. The optimal fermentation process consisted of sequential inoculation with a 31 h delay between inoculations, followed by fermentation for 14.5 d at 18.7 °C, yielding 17.41 ± 0.51 mg/L of PEA, which was 4.6-fold higher than that obtained through the unoptimized fermentation process. Additionally, the CATA results revealed that the cider produced through coculturing was associated with descriptors such as “smooth taste”, “honey”, “pineapple”, and “fruity”, which can be attributed to the high ethyl acetate and PEA levels in the cider.

Optimization of fermentation conditions in Barbari bread based on mixed whole flour (barley and sprouted wheat) and sourdough

The purpose of this study was to use a mixture of whole wheat–barley flour mixture in the preparation of traditional Iranian bread (Barbari) in the optimum condition of fermentation to benefit from all available nutrients. In this study, bread parameters such as specific volume, porosity, textural characteristics, zinc, iron, phytic acid and organoleptic properties were investigated. In this research, different percentages of sourdough (15–30%) and fermentation time (30 – 120 min) were applied. Results showed that the phytic acid content significantly decreased ( p < 0.05) (0.23 – 0.14) by increasing sourdough and fermentation time, which result in increasing in zinc (17.49 – 22.89%) and iron (36.44 – 45.32%) content. Both the sourdough content and fermentation time parameters had a significant effect ( p < 0.05) on the better porosity (9.05 – 13.50%) and overall acceptability of bread (2.15 – 3.85). The hardness, gumminess, chewiness, porosity, phytic acid and overall acceptance parameters were used to optimize the fermentation conditions of Barbari bread by response surface methodology using a central composite design. Optimal conditions for the production of Barbari bread were 29.53% sourdough and 120 min fermentation time. Under optimal conditions, the overall acceptance, hardness, porosity, chewability, gumminess and phytic acid were 3.84, 60.81 N, 14.09%, 302.01 N/mm, 41.37 N and 0.15%, respectively.

Pectinase Production from Banana Peel Biomass via the Optimization of the Solid-state Fermentation Conditions of Aspergillus niger Strain

In this study, the biomass of banana peel was used to produce pectinase via optimization of solid-state fermentation conditions of the filamentous fungi Aspergillus nigeA. niger). The operating conditions of solid-state fermentation were optimized using the method of full factorial design with incubation temperature ranging between 25 °C and 35 °C, moisture content between 40% and 60%, and inoculum size between 1.6 x 106 spores/mL and 1.4 x 107 spores/mL. Optimizing the solid-state fermentation conditions appeared crucial to minimize the sample used in this experimental design and determine the significant correlation between the operating conditions. A relatively high maximal pectinase production of 27 UmL-1 was attained at 35° C of incubation, 60% of moisture content, and 1.6 x 106 spores/mL of inoculum size with a relatively low amount of substrate (5 g). Given that the production of pectinase with other substrates (e.g., pineapple waste, lemon peel, cassava waste, and wheat bran) generally ranges between 3 U/mL and 16 U/mL (Abdullah et al., 2018; Handa et al., 2016; Melnichuk et al., 2020; Thangaratham and Manimegalai, 2014; Salim et al., 2017), thus the yield of pectinase derived from the banana peel in this study (27 U/mL) was considered moderately high. The findings of this study indicated that the biomass of banana peel would be a potential substrate for pectinase production via the solid-state fermentation of A. niger.

How to Harvest Haylage Bales in Sustainable Agriculture

Storing silage in round bales (balage) is a commonly used method for preserving forage for use as stock fodder that has a higher nutritional content than hay. Baling at the optimum density is important for ensuring ideal fermentation conditions. In the manuscript, we present the research methodology and the results of the experiment. We did experiments over the density of haylage bales. We investigated the effect of the moisture content in the harvested material, the length of the cut material and the pressing pressure in the round baler. We used the Barenbrug BG-5 forage mix at different moisture content levels (69, 63, 56, 49, and 42%), that was either unchopped or chopped by the round baler’s cutter bars (312 and 183 mm length) and baled at three different pressing pressures (0.9, 1.4, and 1.8 MPa). The results showed that forage density in the bales reached the highest value at a moisture content of 56% and a pressing pressure of 1.8 MPa, with the forage chopped by the cutter bars.