Assessment of color adsorption by yeast using Grape Skin Agar and impact on red wine color

Aim: Evaluating Saccharomyces cerevisiae strains for their color adsorption aptitude by using Grape Skin Agar in order to protect the phenolic compounds responsible for the color of red wines; proposing a suitable and innovative medium to be included among the tests currently used for wine strain selection.Methods and results: The strains were identified by fluorescence-Internal transcribed spacer (f-ITS) PCR and PCR-Restriction fragment length polymorphism (RFLP), confirmed by sequencing of ITS fragment, and tested for the parameter "aptitude to adsorb polyphenolic compounds" on the innovative chromogenic medium Grape Skin Agar. Laboratory-scale fermentations were carried out in must with and without SO2. The SO2 determined a decrease in tint, color intensity, and total polyphenol content. The strains M2V CHU7 and M2F CHU9 produced wines with the lowest color intensity, with and without SO2, respectively. By contrast, the strains M2F VUP4 and M2V CHU1, with and without SO2, respectively, produced wines with the highest color intensity, and therefore, they could improve the production of red wines.Conclusion: The study highlights great variability and significant differences among strains in regard to their aptitude to modulate wine color. Grape Skin Agar should be a useful medium to be included in the selection tests currently performed for S. cerevisiae strains.Significance and impact of the study: Our study confirms that yeast strains can modulate the chromatic properties of red wines according to their aptitude to adsorb polyphenols, as tested on Grape Skin Agar. Combining colored polyphenolic compound adsorption assay on Petri plate and laboratory-scale fermentation trials provides an effective way to test yeasts for their capability to improve the chromatic quality of the wines

Selection of Wine Saccharomyces cerevisiae Strains and Their Screening for the Adsorption Activity of Pigments, Phenolics and Ochratoxin A

Ochratoxin A is a dangerous mycotoxin present in wines and is considered the principal safety hazard in the winemaking process. Several authors have investigated the ochratoxin A adsorption ability of Saccharomyces cerevisiae yeasts, and specifically selected strains for this desired trait. In the present work, a huge selection of wine yeasts was done starting from Portuguese, Spanish and Italian fermenting musts of dierent cultivars. Firstly, 150 isolates were collected, and 99 non-redundant S. cerevisiae strains were identified. Then, the strains were screened following a multi-step approach in order to select those having primary oenological traits, mainly (a) good fermentation performance, (b) low production of H2S and (c) low production of acetic acid. The preselected strains were further investigated for their adsorption activity of pigments, phenolic compounds and ochratoxin A. Finally, 10 strains showed the desired features. The goal of this work was to select the strains capable of absorbing ochratoxin A but not pigments and phenolic compounds in order to improve and valorise both the quality and safety of red wines. The selected strains are considered good candidates for wine starters, moreover, they can be exploited to obtain a further enhancement of the specific adsorption/non-adsorption activity by applying a yeast breeding approach

Soil biodegradation of nutrients enriched cellulose- and chitosan-derived mulching films for sustainable horticulture

In 2019, global plastics production reached 370 million tons, of which 58 million tons were in Europe[1]. If the plastic use in agriculture accounts for 2% of the global production[2], more than 7 million tons of plastic were used in 2019 in the agricultural sector. Mulch films represent the major source of plastic contamination in agricultural soils[3]. The agricultural surface area covered by plastic films in Europe is four times larger than that covered by greenhouses and six times that of low tunnel hoops. Over the past decades, biodegradable biopolymer mulching films (BPMFs) have been developed to reduce soil pollution by non-biodegradable plastic debris[4] and to expand the circular bioeconomy[5]. In Europe, since 1999, low density polyethylene mulches (LDPMs) have to be dismissed after their use to remove source of pollutants that can reach up to 200 kg ha-1[6] and decline soil quality, crop growth, and yield[7]. BPMFs are a sustainable alternative to conventional LDPMs. Unlike LDPMs, BPMFs, at the end of their lifetime, are tilled into soil where they are expected to be biodegraded by soil microorganisms[8]. Moreover, BPMFs show an estimated saving of about 500 kg of CO2 equivalent per hectare in comparison with LDPMs. Conversely, the impact of LDPMs in intensive horticulture could result higher than weed control by herbicides as by life cycle assessment (LCA)[9]. BPMFs can be obtained by thermo-plasticizing, solvent casting and spraying processes by using renewable and biodegradable raw materials such as starch, cellulose, chitosan, alginate, glucomannan[10] and glycerin as plasticizer[11]. Cellulose and chitosan, being the two most abundant natural biopolymers on Earth, have been proposed as the best candidates for BPMFs production. Unfortunately, the high tendency for intra- and intermolecular hydrogen bonding confers undesirable mechanical properties. The addition of plasticizer as well as fillers overcome this problem[12] modifying mechanical and functional properties of the materials. To sum up, biopolymer blending is an effective strategy to reuse cellulose and chitosan-containing by-products and develop materials with novel mechanical characteristics[13]. Moreover, the functional properties of these materials can be tuned by doping them with suitable compounds[14]. Based on what stated above, and considering that soil fertility, crop growth and yield, are generally N and P limited, the core idea of this project is the preparation of N- and P-enriched BPMFs for soil mulching, in order to slowly release soluble nutrients into soils upon their biodegradation. The latter aspect is of great importance because a proper C:N:P ratio can lead to an increase of soil-dwelling organisms thus contributing to nutrient cycling in the soil-plant system, soil C sequestration and biological fertility status[15]. Moreover, repeated additions of BPMFs over long term can increase the amount of nutrients, thus reducing the use of external inputs (e.g. synthetic fertilizers) within a circular economy perspective. The specific aim of the proposed research are: i) to set up a method for the preparation of suitable BPMFs enriched with N and P; ii) to characterize novel BPMFs and evaluate their structure, degradation kinetics, and isotopic composition iii) to assess the impact of the innovative BPMFs on soil nutrient cycling and crop growth and yield; iv) to evaluate the effect of the innovative BPMFs on soil prokaryotes and micro-arthropods communities; v) to speed-up the biodegradation of the innovative BPMFs by spraying them at the end of their lifecycle with selected microorganisms and by adding the recipient soil with earthworms; vi) to evaluate the innovative BPMFs using the LCA methodology and to investigate its role within the circular economy. Bibliography [1] Plastic Europe, 2020. Website https://www.plasticseurope.org/it/resources/publications/4312-plastics-facts-2020 accessed on 05.01.2021 [2] Vox, G., Loisi, R.V., Blanco, I., Mugnozza, G.S., & Schettini, E. (2016). Agriculture and Agricultural Science Procedia, 8, 583-591. [3] Wenqing, H., Enke, L., Qin, L., Shuang, L., Turner, N., C. & Changrong, Y. 2014. World Agriculture, 4, 3236. [4] Sanchez-Hernandez J.C., Capowiez Y. & Ro K.S., 2020. ACS Sustainable Chemistry & Engineering, 8, 4292-4316. [5] Karan, H., Funk, C., Grabert, M., Oey, M., & Hankamer, B., 2019. Trends in Plant Science, 24, 237-249. [6] Razza, F., Guerrini, S., & Impallari, F.M., 2019. Acta Horticulturae, 1252, 77-84. [7] Hou, L., Xi, J., Chen, X., Li, X., Ma, W., Lu, J., Xu J. & Lin, Y. B, 2019. Journal of Hazardous Materials, 378, 120774. [8] Kyrikou, I., & Briassoulis, D., 2007. Journal of Polymers and the Environment, 15, 125–150 [9] Tasca, A. L., Nessi, S., & Rigamonti, L., 2017. Journal of Cleaner Production, 140, 725-741 [10] Santagata, G., Malinconico, M., Immirzi, B., Schettini, E., Scarascia Mugnozza, G., & Vox, G., 2014. Acta Horticulturae 1037(1037), 921-928. [11] D’Avino, L., Rizzuto, G., Guerrini, S., Sciaccaluga, M., Pagnotta, E., & Lazzeri, L. (2015). Industrial Crops and Products, 75, 29-35. [12] Chen, P., Xie, F., Tang, F., & McNally, T. (2021). Influence of plasticiser type and nanoclay on the properties of chitosan-based materials. European Polymer Journal, 144, 110225. [13] Bajpai, A.K., Shukla, S. K., Bhanu, S., & Kankane, S., 2008. Progress in Polymer Science, 33(11), 1088-1118 [14] Sohaimy, M.I.H.A., & Isa, M.I.N.M. et al., 2020. Polymers. 12, 2487 [15] Cleveland, C.C., & Liptzin, D., 2007. Biogeochemistry 85, 235–25

Wine Yeasts Selection: Laboratory Characterization and Protocol Review

Wine reflects the specificity of a terroir, including the native microbiota. In contrast to the use of Saccharomyces cerevisiae commercial starters, a way to maintain wines’ microbial terroir identities, guaranteeing at the same time the predictability and reproducibility of the wines, is the selection of autochthonous Saccharomyces and non-Saccharomyces strains towards optimal enological characteristics for the chosen area of isolation. This field has been explored but there is a lack of a compendium covering the main methods to use. Autochthonous wine yeasts from different areas of Slovakia were identified and tested, in the form of colonies grown either on nutrient agar plates or in grape must micro-fermentations, for technological and qualitative enological characteristics. Based on the combined results, Saccharomyces cerevisiae PDA W 10, Lachancea thermotolerans 5-1-1 and Metschnikowia pulcherrima 125/14 were selected as potential wine starters. This paper, as a mixture of experimental and review contributions, provides a compendium of methods used to select autochthonous wine yeasts. Thanks to the presence of images, this compendium could guide other researchers in screening their own yeast strains for wine production

Wild Saccharomyces cerevisiae strains display biofilm-like morphology in contact with polyphenols from grapes and wine

Polyphenols are a major component of wine grapes, and contribute to color and flavor, but their influence upon yeast growth forms has not been investigated. In this work we have studied the effect of polyphenols on the ability of natural isolates of wine-related Saccharomyces cerevisiae strains to form biofilms attaching to plastic surfaces, to grow as mat colonies, to invade media, and to display filamentous growth. The use of carbon- and nitrogen-rich or deficient media simulated grape juice fermentation conditions. The addition of wine polyphenols to these media affected biofilm formation, and cells exhibited a wide variety of invasiveness and mat formation ability with associated different growth and footprint patterns. Microscopic observation revealed that some strains switched to filamentous phenotypes which were able to invade media. The wide range of phenotypic expression observed could have a role in selection of strains suitable for inoculated wine fermentations and may explain the persistence of yeast strains in vineyard and winery environments. © 2014 Elsevier B.V

Genetic Improvement of wine yeasts for opposite adsorption activity of phenolics and ochratoxin A during red winemaking

The aim of this research was to acquire new strains of Saccharomyces cerevisiae exhibiting opposite characteristics of cell wall adsorption: very high adsorption activity toward the ochratoxin A, very low adsorption activity toward the pigmented phenolic compounds contained in musts from black grapes. For this purpose, starting from 313 strains of Saccharomyces cerevisiae, 12 strains were pre-selected and used to obtain 27 intraspecific hybrids. Eleven crosses out of 27 were validated as hybrids; the best five hybrids were used in guided winemaking at four Calabrian wineries. The employed experimental protocol has allowed to select yeast strains for their different adsorption activity, improving the strains by spore clone selection and construction of intraspecific hybrids. These results suggest an efficacious way to improve the characteristics of interest in wine yeast

Emerging Trends in Allelopathy: A Genetic Perspective for Sustainable Agriculture

Over the past decades, a growing interest in allelopathy has been recorded due to the effective use of allelochemicals as growth regulators, bioherbicides, insecticides, and antimicrobial crop protection in the sustainable agriculture field. So far, the genetic aspects of the allelopathic effects have been poorly studied, and the identification of allelopathic genes and/or genomic regions (QTLs) has become a challenge to implement specific breeding programs. Here, we review the recent genetic and genome-based research findings in allelopathy, with a particular emphasis on weed control, which is one of the major crop yield-limiting factors. We discuss the key plant–microorganism interactions, including the cross-kingdom RNAi phenomenon and the involvement of microRNAs in allelopathy. Through this review, we wanted to lay the foundation for advancing knowledge in allelopathy and uncover the areas where research is needed

Clonal selection of wine yeasts with differential adsorption activities towards phenolics and ochratoxin

To design a rapid, simple, and low-cost procedure for yeast selection with differential adsorption activities toward phenolics and ochratoxin A, 284 yeast strains were screened. This was done by evaluating the type of growth during grape must fermentation, acetic acid production on Chalk agar, H2S production on BiGGY agar, and spore-formation on acetate agar. After that initial step, 84 strains were pre-selected and further studied by Petri plate tests and to determine their wine-making ability in trials and evaluating their differential adsorption activities toward phenolics and ochratoxin A. Three yeast strains were selected based on the above evaluations. After confirming that they belonged to Saccharomyces cerevisiae species and were diploids, a spore clonal selection was performed. The strain Sc1741A_1D was selected and used in winemaking at six Calabrian wineries and found to be suitable as wine starter to improve quality and safety of red wines

Ochratoxin A adsorption phenotype: an inheritable yeast trait

21st International ICFMH Symposium “Evolving Microbial Food Quality and Safety” Aberdeen 1st – 4th Septembe

Ochratoxin A adsorption phenotype: an inheritable yeast trait

This study aimed to evaluate the inheritance of the trait ochratoxin A adsorption in two wine strains of Saccharomyces cerevisiae and their 46 descendants. Each strain was inoculated intriplicate in test tubes containing 10 mL of must obtained from the Calabrian Zibibbo white grape variety, artificially contaminated with ochratoxin A to reach a total content of 4.10 ng/mL. Themicrovinification trials were performed at 25°C. After 30 days, ochratoxin A values ranged from 0.74 to 3.18 ng/mL, from 0.01 to 2.69 ng/mL, and from 0.60 to 2.95 ng/mL respectively in wines,in lees after washing, and in the saline solution used to wash the lees. The analysis of OTA in wines was performed to find the residual toxin content after yeast activity, thus obtainingtechnological evidence of yeast influence on wine detoxification. The analysis of OTA in lees after washing was performed to distinguish the OTA linked to cells. The analysis of OTA in thesaline solution used to wash the lees was performed to distinguish the OTA adsorbed on yeast cell walls and removed by washing, thus focusing on the adsorption activity of wine yeastthrough electrostatic and ionic interactions between parietal mannoproteins and OTA. Ploidy of the two parental strains was controlled by flow cytometry. Results demonstrated that theochratoxin A adsorption is genetically controlled and is a polygenic inheritable trait of wine yeasts. The majority of the descendants are characterized by a great and significant diversitycompared to their parents. Both the parental strains had genome sizes consistent with their being diploid, so validating the observed results. These findings constitute an initial step to demonstrate the mechanisms of inheritance and establish breeding strategies to improve the ochratoxin A adsorption trait in wine yeasts. This will allow a decrease in the ochratoxin A content of contaminated musts during winemaking, by using genetically improved wine yeasts