Managing Your Wine Fermentation to Reduce the Risk of Biogenic Amine Formation

Biogenic amines are nitrogenous organic compounds produced in wine from amino acid precursors mainly by microbial decarboxylation. The concentration of biogenic amines that can potentially be produced is dependent on the amount of amino acid precursors in the medium, the presence of decarboxylase positive microorganisms and conditions that enable microbial or biochemical activity such as the addition of nutrients to support the inoculated starter cultures for alcoholic and malolactic fermentation (MLF). MLF can be conducted using co-inoculation or an inoculation after the completion of alcoholic fermentation that may also affect the level of biogenic amines in wine. This study focused on the impact of the addition of complex commercial yeast and bacterial nutrients and the use of different MLF inoculation scenarios on the production of biogenic amines in wine. Results showed that the addition of complex nutrients to real grape must could potentially increase histamine concentrations in wine. The same experiment in synthetic grape must showed a similar trend for putrescine and cadaverine. The effect of different MLF inoculation scenarios was examined in two cultivars, Pinotage and Shiraz. Conflicting results was obtained. In the Shiraz, co-inoculation resulted in lower biogenic amine concentrations after MLF compared to before MLF, while the concentration was higher in the Pinotage. However, the production of biogenic amines was affected more by the presence of decarboxylase positive lactic acid bacteria than by the addition of complex nutrients or the inoculation scenario

Transcriptional and Metabolic Response of Wine-Related Lactiplantibacillus plantarum to Different Conditions of Aeration and Nitrogen Availability

Lactic acid bacteria (LAB) perform the process of malolactic fermentation (MLF) in wine. Availability of oxygen and nitrogen nutrients could influence LAB growth, malolactic activity, and other metabolic pathways, impacting the subsequent wine quality. The impact of these two factors has received limited investigation within LAB, especially on a transcriptome level. The aim of this study was to evaluate metabolic changes in the strain Lactiplantibacillus plantarum IWBT B063, growing in synthetic grape juice medium (GJM) under different oxygen exposure conditions, and with low availability of nitrogen-based nutrients. Next-generation sequencing was used to analyze expression across the transcriptome (RNA-seq), in combination with conventional microbiological and chemical analysis. L. plantarum consumed the malic acid present in all the conditions evaluated, with a slight delay and impaired growth for nitrogen limitation and for anaerobiosis. Comparison of L. plantarum transcriptome during growth in GJM with and without O-2 revealed differential expression of 148 functionally annotated genes, which were mostly involved in carbohydrate metabolism, genetic information processing, and signaling and cellular processes. In particular, genes with a protective role against oxidative stress and genes related to amino acid metabolism were differentially expressed. This study confirms the suitability of L. plantarum IWBT B063 to carry out MLF in different environmental conditions due to its potential adaption to the stress conditions tested and provides a better understanding of the genetic background of an industrially relevant strain

Transcriptomics unravels the adaptive molecular mechanisms of Brettanomyces bruxellensis under SO2 stress in wine condition

CITATION: Valdetara, F. et al. 2020. Transcriptomics unravels the adaptive molecular mechanisms of Brettanomyces bruxellensis under SO2 stress in wine condition. Food Microbiology, 90. doi:10.1016/j.fm.2020.103483.The original publication is available at https://www.sciencedirect.com/journal/food-microbiologySulfur dioxide is generally used as an antimicrobial in wine to counteract the activity of spoilage yeasts, including Brettanomyces bruxellensis. However, this chemical does not exert the same effectiveness on different B. bruxellensis yeasts since some strains can proliferate in the final product leading to a negative sensory profile due to 4-ethylguaiacol and 4-ethylphenol. Thus, the capability of deciphering the general molecular mechanisms characterizing this yeast species’ response in presence of SO2 stress could be considered strategic for a better management of SO2 in winemaking. A RNA-Seq approach was used to investigate the gene expression of two strains of B. bruxellensis, AWRI 1499 and CBS 2499 having different genetic backgrounds, when exposed to a SO2 pulse. Results revealed that sulphites affected yeast culturability and metabolism, but not volatile phenol production suggesting that a phenotypical heterogeneity could be involved for the SO2 cell adaptation. The transcriptomics variation in response to SO2 stress confirmed the strain-related response in B. bruxellensis and the GO analysis of common differentially expressed genes showed that the detoxification process carried out by SSU1 gene can be considered as the principal specific adaptive response to counteract the SO2 presence. However, nonspecific mechanisms can be exploited by cells to assist the SO2 tolerance; namely, the metabolisms related to sugar alcohol (polyols) and oxidative stress, and structural compounds.https://www.sciencedirect.com/science/article/pii/S0740002020300721?via%3DihubPublishers versio

Comparative morphological characteristics of three Brettanomyces bruxellensis wine strains in the presence/absence of sulfur dioxide

International audienceThe red wine spoilage yeast Brettanomyces bruxellensis has been the subject of numerous investigations. Some of these studies focused on spoilage mechanisms, sulfur dioxide tolerance and nutrient requirements. Pseudomycelium formation, although a striking feature of this species, has however been poorly investigated. Furthermore, literature regarding the induction mechanism of pseudomycelium formation in this yeast is limited and lacks clarity, as results published are contradictory. This study elucidates this phenomenon among strains from geographically different areas. Potential environmental cues were investigated, to attain a better understanding of this mechanism and its role as a survival strategy. SO2 was previously reported to induce this morphological change however results obtained in this study did not support this. Nevertheless, the results obtained using scanning and transmission electron microscopy illustrate, for the first time in this yeast, deformity to the cell membrane and alterations to the fibrillar layers in SO2 treated cells. In addition, the SO2 exposed cultures displayed cell size variations, with cells displaying a decrease in length as well as delayed growth, with a prolonged lag phase. Fluorescence microscopy demonstrated a decrease in metabolic activity and the appearance of inclusion body-like structures in the cells following exposure to SO2

Is UV the answer to combat microbial spoilage?

Microorganisms certainly play a crucial role in wine production (Mauriello et al., 2009; Ruiz et al., 2010), however some yeasts and bacteria can have a negative impact on the quality of wine due to spoilage (du Toit and Pretorius, 2000). Good hygiene practices together with excellent winemaking procedures are recommended in the cellar to continuously control the growth of microorganisms throughout wine production. Traditionally, microbial growth is effectively controlled in grape juice and wine by the addition of sulphur dioxide (SO2). Since more consumers are allergic to SO2, its use is currently under review (Jackson, 1994). Besides SO2 usage, alternative additives such as potassium sorbate, Velcorin? (dimethyl dicarbonate), natamycin and lysozyme are also known to have inhibitory effects on microorganisms. Filtration is also very efficient in controlling microbial growth but, can however affect the colour, flavour and palate of wine negatively (Su?rez et al., 2007). Ultraviolet (UV-C) radiation along with flash pasteurisation, pulsed electric fields (PEF) and high hydrostatic pressure systems are classified as innovative technologies with the potential of inactivating microorganisms in liquid food products without affecting the sensorial properties of the product (Sizer and Balasubramaniam, 1999; Pu?rtolas et al., 2009). The effectiveness of UV-C radiation to inactivate microorganisms has already been investigated in a range of fruit juices, beer and milk (Koutchma et al., 2009; Lu et al., 2010). However, the feasibility of this technology to control wine-related microorganisms in grape juice and wine is still unclear. The aim of the study was therefore to investigate the efficacy of UV-C radiation as an alternative technology to inactivate microorganisms in red and white grapes juices and wine

Designer Yeasts for the Fermentation Industry of the 21st Century

The budding yeast, Saccharomyces cerevisiae, has enjoyed a long and distinguished history in the fermention industry. Owing to its efficiency in producing alcohol, S. cerevisiae is, without doubt, the most important commercial microorganism with GRAS (Generally Regarded As Safe) status. By brewing beer and sparkling wine, mankind’s oldest domesticated organism made possible the world’s first biotechnological processes. With the emergence of modern molecular genetics, S. cerevisiae has again been harnessed to shift the frontiers of mankind’s newest revolution, genetic engineering. S. cerevisiae is at the forefront of many of these developments in modern biotechnology. Consequently, the industrial importance of S. cerevisiae has extended beyond traditional fermentation. Today, the products of yeast biotechnologies impinge on many commercially important sectors, including food, beverages, biofuels, chemicals, industrial enzymes, pharmaceuticals, agriculture and the environment. Nevertheless, since ethyl alcohol produced by yeast fermentation is likely to remain the foremost worldwide biotechnological commodity for the foreseeable future, this review focuses on advances made with respect to the development of tailor- made yeast strains for the fermented beverage and biofuel industries

PCR-based DGGE fingerprinting and identification of the microbial population in South African red grape must and wine

Aim: The aim of this study was to evaluate the microbial population present in red grape must and wine using polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE). Methods and results: Red wine from the cultivars Pinotage and Merlot were produced and samples taken throughout alcoholic and malolactic fermentation (MLF). PCR fragments were resolved by DGGE and unique fingerprints were obtained for the bacteria and yeasts present in the wines. Lactobacillus plantarum, Enterobacter sakazakii (Cronobacter sp.) and Pantoea agglomerans were present in the Pinotage during both alcoholic and MLF, and in both inoculated and spontaneous fermentations. E. sakazakii (Cronobacter sp.) and P. agglomerans were also observed in the Merlot wines during alcoholic fermentation as well as MLF. Saccharomyces cerevisiae was the most dominant yeast observed in Pinotage, and was the only yeast observed in Merlot. This yeast was observed until the end of MLF. Conclusions: Results showed that the microbial flora that participates in the winemaking process is more diverse than commonly thought. Significance and impact of the study: This method may serve as an alternative to conventional microbiological methods for the identification of the microbial species in red grape must and wine

Efficacy of ultraviolet radiation as an alternative technology to inactive microorganisms in grape juices and wines

Since sulphur dioxide (SO2) is associated with health risks, the wine industry endeavours to reduce SO2 levels in wines with new innovative techniques. The aim of this study was, therefore, to investigate the efficacy of ultraviolet radiation (UV)-C (254 nm) as an alternative technology to inactivate microorganisms in grape juices and wines.A pilot-scale UV-C technology (SurePure, South Africa) consisting of an UV-C germicidal lamp (100 W output; 30 W UV-C output) was used to apply UV-C dosages ranging from 0 to 3672 J l−1, at a constant flow rate of 4000 l h−1 (Re > 7500). Yeasts, lactic and acetic acid bacteria were singly and co-inoculated into 20 l batches of Chenin blanc juice, Shiraz juice, Chardonnay wine and Pinotage wine, respectively. A dosage of 3672 J l−1, resulted in an average log10 microbial reduction of 4.97 and 4.89 in Chardonnay and Pinotage, respectively. In Chenin blanc and Shiraz juice, an average log10 reduction of 4.48 and 4.25 was obtained, respectively. UV-C efficacy may be influenced by liquid properties such as colour and turbidity. These results had clearly indicated significant (p < 0.05) germicidal effect against wine-specific microorganisms; hence, UV-C radiation may stabilize grape juice and wine microbiologically in conjunction with reduced SO2 levels.Mr Guy Kebble (SurePure, Milnerton, South Africa) and Cape Peninsula University of Technology and the National Department of Agriculture, Forestry and Fisherie

The grapevine and wine microbiome : insights from high-throughput amplicon sequencing

CITATION: Morgan, H. H., Du Toit, M. & Setati, M. E. 2017. The grapevine and wine microbiome : insights from high-throughput amplicon sequencing. Frontiers in Microbiology, 8:820, doi:10.3389/fmicb.2017.00820.The original publication is available at https://www.frontiersin.orgFrom the time when microbial activity in wine fermentation was first demonstrated, the microbial ecology of the vineyard, grape, and wine has been extensively investigated using culture-based methods. However, the last 2 decades have been characterized by an important change in the approaches used for microbial examination, due to the introduction of DNA-based community fingerprinting methods such as DGGE, SSCP, T-RFLP, and ARISA. These approaches allowed for the exploration of microbial community structures without the need to cultivate, and have been extensively applied to decipher the microbial populations associated with the grapevine as well as the microbial dynamics throughout grape berry ripening and wine fermentation. These techniques are well-established for the rapid more sensitive profiling of microbial communities; however, they often do not provide direct taxonomic information and possess limited ability to detect the presence of rare taxa and taxa with low abundance. Consequently, the past 5 years have seen an upsurge in the application of high-throughput sequencing methods for the in-depth assessment of the grapevine and wine microbiome. Although a relatively new approach in wine sciences, these methods reveal a considerably greater diversity than previously reported, and identified several species that had not yet been reported. The aim of the current review is to highlight the contribution of high-throughput next generation sequencing and metagenomics approaches to vineyard microbial ecology especially unraveling the influence of vineyard management practices on microbial diversity.https://www.frontiersin.org/articles/10.3389/fmicb.2017.00820/fullPublisher's versio