Isolation of Saccharomyces cerevisiae strains producing higher levels of flavoring compounds for production of "cachaça" the Brazilian sugarcane spirit

Selected cachaça yeast strains share a genomic profile related to traits relevant to industrial fermentation processes

The isolation and selection of yeast strains to improve the quality of the cachaça-Brazilian Spirit-have been studied in our research group. Our strategy considers Saccharomyces cerevisiae as the predominant species involved in sugarcane juice fermentation and the presence of different stressors (osmolarity, temperature, ethanol content, and competition with other microorganisms). It also considers producing balanced concentrations of volatile compounds (higher alcohols and acetate and/or ethyl esters), flocculation capacity, and ethanol production. Since the genetic bases behind these traits of interest are not fully established, the whole genome sequencing of 11 different Saccharomyces cerevisiae strains isolated and selected from different places was analyzed to identify the presence of a specific genetic variation common to cachaça yeast strains. We have identified 20,128 single-nucleotide variants shared by all genomes. Of these shared variants, 37 were new variants (being six missenses), and 4,451 were identified as missenses. We performed a detailed functional annotation (using enrichment analysis, protein-protein interaction network analysis, and database and in-depth literature searches) of these new and missense variants. Many genes carrying these variations were involved in the phenotypes of flocculation, tolerance to fermentative stresses, and production of volatile compounds and ethanol. These results demonstrate the existence of a genetic profile shared by the 11 strains under study that could be associated with the applied selective strategy. Thus, this study points out genes and variants that may be used as molecular markers for selecting strains well suited to the fermentation process, including genetic improvement by genome editing, ultimately producing high-quality beverages and adding value.IMPORTANCEThis work demonstrates the existence of new genetic markers related to different phenotypes used to select yeast strains and mutations in genes directly involved in producing flavoring compounds and ethanol, and others related to flocculation and stress resistance.

Performance and robustness analysis reveals phenotypic trade-offs in yeast

To design strains that can function efficiently in complex industrial settings, it is crucial to consider their robustness, that is, the stability of their performance when faced with perturbations. In the present study, we cultivated 24 Saccharomyces cerevisiae strains under conditions that simulated perturbations encountered during lignocellulosic bioethanol production, and assessed the performance and robustness of multiple phenotypes simultaneously. The observed negative correlations confirmed a trade-off between performance and robustness of ethanol yield, biomass yield, and cell dry weight. Conversely, the specific growth rate performance positively correlated with the robustness, presumably because of evolutionary selection for robust, fast-growing cells. The Ethanol Red strain exhibited both high performance and robustness, making it a good candidate for bioproduction in the tested perturbation space. Our results experimentally map the robustness-performance trade-offs, previously demonstrated mainly by single-phenotype and computational studies.

Online monitoring of higher alcohols and esters throughout beer fermentation by commercial Saccharomyces cerevisiae and Saccharomyces pastorianus yeast

Higher alcohols and esters are among the predominant classes of volatile organic compounds (VOCs) that influence the quality of beer. The concentrations of these compounds are determined through a specific yeast strain selection and fermentation conditions. The effect of yeast strains on the formation of higher alcohols and esters throughout fermentations (at 20°C) was investigated. Flavour-relevant esters (ethyl acetate, isoamyl acetate, ethyl hexanoate and ethyl octanoate) and higher alcohols (isoamyl alcohol, isobutyl alcohol and phenylethyl alcohol) were monitored throughout the fermentation using proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) coupled with an automated sampling system for continuous measurements. Compound identification was confirmed by analysis of samples using gas chromatography-mass spectrometry (GC-MS). Results demonstrated the specific time points where variation in higher alcohol and ester generation between yeast strains occurred. In particular, the concentrations of isoamyl acetate, ethyl octanoate and isoamyl alcohol between yeast strains were significantly different over the first 2 days of fermentation; whereas, after Day 3, no significant differences were observed. The two Saccharomyces pastorianus strains produced comparable concentrations of the key higher alcohols and esters. However, the key higher alcohol and ester concentrations varied greatly between the two S. cerevisiae strains. The use of PTR-ToF-MS to rapidly measure multiple yeast strains provides new insights on fermentation for brewers to modify the sensory profile and optimise quality.

An Overview of Spirits Made from Sugarcane Juice

Among the family of sugarcane spirits, those made from juice are diverse and often produced in a traditional way. They must be distinguished from other sugarcane spirits, which are more widely produced and made from other sugarcane derivatives, such as molasses. These alcoholic beverages contribute significantly to the socio-economic development of many countries. However, despite ancestral know-how, there is a lack of contemporary data required to characterize some sugarcane juice spirits (SCJSs) and to overcome the current and future threats that producers will have to face. While preserving their authenticity and specificity, SCJS producers expect to improve and ensure sufficient yield and a superior quality product. Even if the scientific knowledge on these spirits is not comparable, the available data could help identify the critical points to be improved in the making process. This review aims to present the main SCJSs encountered worldwide, defining their specific features through some important aspects with, notably, references to the complex notion of terroir. To continue, we discuss the main steps of the SCJS process from harvesting to aging. Finally, we expose an inventory of SCJS's chemical compositions and of their sensory description that define the specific organoleptic properties of these spirits.

The Spirit of Cachaça Production: An Umbrella Review of Processes, Flavour, Contaminants and Quality Improvement

This review provides a comprehensive analysis of the production, classification, and quality control of cachaça, a traditional Brazilian sugarcane spirit with significant cultural importance. It explores the fermentation and distillation of sugarcane juice, the ageing process in wooden containers, and the regulatory aspects of cachaça labelling. It emphasises the role of quality control in maintaining the spirit's integrity, focusing on monitoring copper levels in distillation stills. Ethyl carbamate (EC), a potential carcinogen found in cachaça, is investigated, with the study illuminating factors influencing its formation and prevalence and the importance of its vigilant monitoring for ensuring safety and quality. It also underscores the control of multiple parameters in producing high-quality cachaça, including raw material selection, yeast strains, acidity, and contaminants. Further, the impact of ageing, wood cask type, and yeast strains on cachaça quality is examined, along with potential uses of vinasse, a cachaça by-product, in yeast cell biomass production and fertigation. A deeper understanding of the (bio)chemical and microbiological reactions involved in cachaça production is essential to facilitate quality control and standardisation of sensory descriptors, promoting global acceptance of cachaça. Continued research will address safety concerns, improve quality, and support the long-term sustainability and success of the cachaça industry.

Isolation, Identification, Optimization of Baker’s Yeast from Natural Sources, Scale-Up Production Using Molasses as a Cheap Carbohydrate Source, and Evaluation for Bread Production

(1) Background: Bangladesh must has to spend a large amount of foreign currency to import commercial baker’s yeast every year. We could save money by finding a potential Saccharomyces cerevisiae from natural sources compatible with commercial baker’s yeast production. (2) Methods: Grapes, rice, pineapples were collected, processed, and inoculated on YMA plates and incubated at 30 °C for 48 h. Then 11 single morphologically well-formed colonies were isolated, purified, and identified, three as S. cerevisiae, three as S. rouxii, three as S. bisporus, and two as S. exigus based on standard cultural, morphological, and biochemical characteristics. Identified S. cerevisiae (designated as G2, P5 and R3) were then assessed for CO2 production as a measure of their baking potential during bread production and compared with two commercial strains (designated as C1 and C2). (3) Results: Isolate-G2 produced the maximum of 1830 mm3 of gas, whereas C1, C2, R3, and P5 produced 1520, 1680, 770, and 610 mm3 gas, respectively. No strain produced H2S which is associated with an off-flavor and unpleasant taste. These isolates showed maximum cell density at a pH range of 4–5.5 in 4–16% molasses broth at 30 °C after 4 days of incubation and maximum 4.75 × 109, 7.9 × 108, 1.472 × 1010, 2.08 × 1010 and 5.24 × 109 CFU mL−1 were produced by C1, C2, G2, P5 and R3, respectively. Isolate-G2 was found to have the most potential, whereas isolate-R3 and P5 have satisfactory potential. (4) Conclusions: G2 could be a good candidate for commercial trials.

Lager-brewing yeasts in the era of modern genetics

The yeast Saccharomyces pastorianus is responsible for the annual worldwide production of almost 200 billion liters of lager-type beer. S. pastorianus is a hybrid of Saccharomyces cerevisiae and Saccharomyces eubayanus that has been studied for well over a century. Scientific interest in S. pastorianus intensified upon the discovery, in 2011, of its S. eubayanus ancestor. Moreover, advances in whole-genome sequencing and genome editing now enable deeper exploration of the complex hybrid and aneuploid genome architectures of S. pastorianus strains. These developments not only provide novel insights into the emergence and domestication of S. pastorianus but also generate new opportunities for its industrial application. This review paper combines historical, technical and socioeconomic perspectives to analyze the evolutionary origin and genetics of S. pastorianus. In addition, it provides an overview of available methods for industrial strain improvement and an outlook on future industrial application of lager-brewing yeasts. Particular attention is given to the ongoing debate on whether current S. pastorianus originates from a single or multiple hybridization events and to the potential role of genome editing in developing industrial brewing yeast strains.

New Lager Brewery Strains Obtained by Crossing Techniques Using Cachaça (Brazilian Spirit) Yeasts

The development of hybrids has been an effective approach to generate novel yeast strains with optimal technological profile for use in beer production. This study describes the generation of a new yeast strain for lager beer production by direct mating between two Saccharomyces cerevisiae strains isolated from cachaça distilleries: one that was strongly flocculent, and the other with higher production of acetate esters. The first step in this procedure was to analyze the sporulation ability and reproductive cycle of strains belonging to a specific collection of yeasts isolated from cachaça fermentation vats. Most strains showed high rates of sporulation, spore viability, and homothallic behavior. In order to obtain new yeast strains with desirable properties useful for lager beer production, we compare haploid-to-haploid and diploid-to-diploid mating procedures. Moreover, an assessment of parental phenotype traits showed that the segregant diploid C2-1d generated from a diploid-to-diploid mating experiment showed good fermentation performance at low temperature, high flocculation capacity, and desirable production of acetate esters that was significantly better than that of one type lager strain. Therefore, strain C2-1d might be an important candidate for the production of lager beer, with distinct fruit traces and originating using a non-genetically modified organism (GMO) approach.IMPORTANCE Recent work has suggested the utilization of hybridization techniques for the generation of novel non-genetically modified brewing yeast strains with combined properties not commonly found in a unique yeast strain. We have observed remarkable traits, especially low temperature tolerance, maltotriose utilization, flocculation ability, and production of volatile aroma compounds, among a collection of Saccharomyces cerevisiae strains isolated from cachaça distilleries, which allow their utilization in the production of beer. The significance of our research is in the use of breeding/hybridization techniques to generate yeast strains that would be appropriate for producing new lager beers by exploring the capacity of cachaça yeast strains to flocculate and to ferment maltose at low temperature, with the concomitant production of flavoring compounds.

Quality improvement and geographical indication of cachaça (Brazilian spirit) by using locally selected yeast strains

AIMS

In order to improve the quality and to create a biological basis for obtainment of the protected denomination of origin (PDO), indigenous yeast were isolated and characterized for use in Salinas city (the Brazilian region of quality cachaça production).

MATERIAL AND METHODS

Seven thousand and two hundred yeast colonies from 15 Salinas city distilleries were screened based on their fermentative behaviour and the physicochemical composition of cachaça. Molecular polymorphic analyses were performed to characterize these isolates.

RESULTS

Two Saccharomyces cerevisiae strains (nos. 678 and 680) showed appropriate characteristics to use in the cachaça production: low levels of acetaldehyde and methanol, and high ethyl lactate/ethyl acetate ratio respectively. They also presented polymorphic characteristics more closely related between themselves even when compared to other strains from Salinas.

CONCLUSIONS

The application of selected yeast to cachaça production can contribute for the improvement of the quality product as well as be used as a natural marker for PDO.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study suggests that the use of selected yeast strains could contribute to obtain a cachaça similar to those produced traditionally, while getting wide acceptation in the market, yet presenting more homogeneous organoleptic characteristics, and thus contributing to the PDO implementation.

Sugar cane spirit (cachaça): Effects of mixed inoculum of yeasts on the sensory and chemical characteristics

The main goal of this study was to produce cachaça using a mixed inoculum of Saccharomyces cerevisiae and Meyerozyma caribbica and characterize the produced beverage using HPLC, GC-FID, GC-MS and sensorial analysis. Additionally, the use of MALDI-TOF as a tool to characterize and monitor pure and mixed inocula fermenting sugar cane juice was also evaluated. Vat fermentations were carried out for three consecutive batches using autoclaved 16°Brix sugar cane juice fermented by a mixed inoculum of M. caribbica 10⁷ cells/mL and S. cerevisiae 10⁸ cells/mL. The cachaça produced by the mixed culture of M. caribbica and S. cerevisiae showed the highest concentration of volatile compounds associated with good sensory descriptors such as ethyl hexanoate (114.11μg/L), 2-phenylethyl acetate (2.77μg/L), a-terpineol (0.45μg/L), b-citronellol (2.47μg/L), and geraniol (0.24μg/L). This beverage consequently showed greater acceptance in the sensorial analysis for taste and aroma, especially by younger panelists. The feasibility of MALDI-TOF use under studied conditions was demonstrated by the comparison of the results obtained from yeast cultivation in YPD broth, YPD agar and sugar cane juice, showing that there was no interference of sugar cane juice in protein profile. The results obtained from MALDI-TOF analysis showed that the protein extraction directly from sugar cane juice under fermentation, without the traditional plating step, allowed the distinction between mixed and pure inocula even under different M. caribbica populations and Brix degrees.

Biotechnological potential of yeast isolates from cachaça: the Brazilian spirit

This study identified phenotypic traits appropriate for biotechnological applications of 118 yeasts isolated from cachaça distilleries. Different properties were verified: capacity to use alternative carbon sources; ability to tolerate high concentrations of sucrose, ethanol, methanol, aluminum and zinc as well as different pH values and foam production. Pichia guilliermondii and Pichia anomala strains were identified as the most promising ones for application in the second-generation biofuel industry, showing ability to grow on high glycerol concentrations. Other isolates, identified as Saccharomyces cerevisiae, produced bioethanol comparable to the industrial strains, and were therefore ideal for use in the first-generation ethanol industry. Some of these strains also showed high resistance to aluminum, as observed in sugarcane juice, and to inter-cycle washings with diluted sulphuric acid, as performed in the industrial bioethanol production process. In summary, yeast isolates from cachaça distilleries displayed robustness and phenotypic plasticity, which makes them interesting for biotechnological applications.

Variable flocculation profiles of yeast strains isolated from cachaça distilleries

In cachaça production, the use of yeast cells as starters with predictable flocculation behavior facilitates the cell recovery at the end of each fermentation cycle. Therefore, the aim of this work was to explain the behavior of cachaça yeast strains in fermentation vats containing sugarcane through the determination of biochemical and molecular parameters associated with flocculation phenotypes. By analyzing thirteen cachaça yeast strains isolated from different distilleries, our results demonstrated that neither classic biochemical measurements (e.g., percentage of flocculation, EDTA sensitivity, cell surface hydrophobicity, and sugar residues on the cell wall) nor modern molecular approaches, such as polymerase chain reaction (PCR) and real-time PCR (q-PCR), were sufficient to distinctly classify the cachaça yeast strains according to their flocculation behavior. It seems that flocculation is indeed a strain-specific phenomenon that is difficult to explain and/or categorize by the available methodologies.

Improving industrial yeast strains: exploiting natural and artificial diversity

Yeasts have been used for thousands of years to make fermented foods and beverages, such as beer, wine, sake, and bread. However, the choice for a particular yeast strain or species for a specific industrial application is often based on historical, rather than scientific grounds. Moreover, new biotechnological yeast applications, such as the production of second-generation biofuels, confront yeast with environments and challenges that differ from those encountered in traditional food fermentations. Together, this implies that there are interesting opportunities to isolate or generate yeast variants that perform better than the currently used strains. Here, we discuss the different strategies of strain selection and improvement available for both conventional and nonconventional yeasts. Exploiting the existing natural diversity and using techniques such as mutagenesis, protoplast fusion, breeding, genome shuffling and directed evolution to generate artificial diversity, or the use of genetic modification strategies to alter traits in a more targeted way, have led to the selection of superior industrial yeasts. Furthermore, recent technological advances allowed the development of high-throughput techniques, such as 'global transcription machinery engineering' (gTME), to induce genetic variation, providing a new source of yeast genetic diversity.

Technological properties of indigenous wine yeast strains isolated from wine production regions of Turkey

The purpose of this study was to evaluate the important technological and fermentative properties of wine yeast strains previously isolated from different wine producing regions of Turkey. The determination of the following important properties was made: growth at high temperatures; fermentative capability in the presence of high sugar concentration; fermentation rate; hydrogen sulfide production; killer activity; resistance to high ethanol and sulfur dioxide; foam production; and enzymatic profiles. Ten local wine yeast strains belonging to Saccharomyces, and one commercial active dry yeast as a reference strain were evaluated. Fermentation characteristics were evaluated in terms of kinetic parameters, including ethanol yield (YP/S), biomass yield (YX/S), theoretical ethanol yield (%), specific ethanol production rate (qp; g/gh), specific glucose uptake rate (qs; g/gh), and the substrate conversion (%). All tested strains were able to grow at 37 °C and to start fermentation at 30° Brix, and were resistant to high concentrations of sulfur dioxide. 60 % of the strains were weak H2S producers, while the others produced high levels. Foam production was high, and no strains had killer activity. Six of the tested strains had the ability to grow and ferment at concentrations of 14 % ethanol. Except for one strain, all fermented most of the media sugars at a high rate, producing 11.0-12.4 % (v/v) ethanol. Although all but one strain had suitable characteristics for wine production, they possessed poor activities of glycosidase, esterase and proteinase enzymes of oenological interest. Nine of the ten local yeast strains were selected for their good oenological properties and their suitability as a wine starter culture.

Two interbreeding populations of Saccharomyces cerevisiae strains coexist in cachaça fermentations from Brazil

In this study, the phylogenetic relationships between cachaça strains of Saccharomyces cerevisiae isolated from different geographical areas in Brazil were obtained on the basis of sequences of one mitochondrial (COX2) and three nuclear (EGT2, CAT8, and BRE5) genes. This analysis allowed us to demonstrate that different types of strains coexist in cachaça fermentations: wine strains, exhibiting alleles related or identical to those present in European wine strains; native strains, containing alleles similar to those found in strains isolated from traditional fermentations from Latin America, North America, Malaysian, Japan, or West Africa; and their intraspecific hybrids or 'mestizo' strains, heterozygous for both types of alleles. Wine strains and hybrids with high proportions of wine-type alleles predominate in southern and southeastern Brazil, where cachaça production coexists with winemaking. The high frequency of 'wine-type' alleles in these regions is probably due to the arrival of wine immigrant strains introduced from Europe in the nearby wineries due to the winemaking practices. However, in north and northeastern states, regions less suited or not suited for vine growing and winemaking, wine-type alleles are much less frequent because 'mestizo' strains with intermediate or higher proportions of 'native-type' alleles are predominant.

Exploration of potential baker's yeast from sugarcane juice: optimization and evaluation

The present study was carried out to explore baker's yeasts strains from sugarcane juice to assess its potential in laboratory scale production of breads. Collected juice samples were processed for isolation and identification of yeast strains based on standard cultural, morphological and biochemical characteristics. Among the six isolated strains, four (designated as S1, S2, S5 and S6) were identified as Saccharomyces cerevisiae and the rests (designated S3 and S4) were as S. rouxii. When assessing their CO2 production rates as a measure of their baking potential, S6 was found to produce maximum amount of gas (226.67 mm3 mL(-1)) in sucrose broth, whereas gas produced by S2, S1 and S5 were relatively insignificant (170, 136.67 and 86.67 mm3 mL(-1), respectively). No strain was found to produce undesirable H2S gas responsible for off-flavor. Besides, effects of different physicochemical parameters (e.g., pH, temperature, substrate concentration, incubation period, agitation etc.) on the production of yeast cell-mass were studied. Yield of cell mass was indirectly measured by spectrophotometric method at 550 nm. All the test isolates were found to produce maximum cell mass at a pH range of 4.0 to 5.0 in 2 to 4% molasses broth at 30 degrees C after 4 days of incubation. In the laboratory scale production of bread using composite flour, Isolate-S6 formed significant characteristic texture. Considering overall characteristics, Isolate- S6 was found to be satisfactorily potent for baking purpose.

Flavour-active wine yeasts

The flavour of fermented beverages such as beer, cider, saké and wine owe much to the primary fermentation yeast used in their production, Saccharomyces cerevisiae. Where once the role of yeast in fermented beverage flavour was thought to be limited to a small number of volatile esters and higher alcohols, the discovery that wine yeast release highly potent sulfur compounds from non-volatile precursors found in grapes has driven researchers to look more closely at how choice of yeast can influence wine style. This review explores recent progress towards understanding the range of ‘flavour phenotypes’ that wine yeast exhibit, and how this knowledge has been used to develop novel flavour-active yeasts. In addition, emerging opportunities to augment these phenotypes by engineering yeast to produce so-called grape varietal compounds, such as monoterpenoids, will be discussed.

High hydrostatic pressure activates gene expression that leads to ethanol production enhancement in a Saccharomyces cerevisiae distillery strain

High hydrostatic pressure (HHP) is a stress that exerts broad effects on microorganisms with characteristics similar to those of common environmental stresses. In this study, we aimed to identify genetic mechanisms that can enhance alcoholic fermentation of wild Saccharomyces cerevisiae isolated from Brazilian spirit fermentation vats. Accordingly, we performed a time course microarray analysis on a S. cerevisiae strain submitted to mild sublethal pressure treatment of 50 MPa for 30 min at room temperature, followed by incubation for 5, 10 and 15 min without pressure treatment. The obtained transcriptional profiles demonstrate the importance of post-pressurisation period on the activation of several genes related to cell recovery and stress tolerance. Based on these results, we over-expressed genes strongly induced by HHP in the same wild yeast strain and identified genes, particularly SYM1, whose over-expression results in enhanced ethanol production and stress tolerance upon fermentation. The present study validates the use of HHP as a biotechnological tool for the fermentative industries.

Strategies to select yeast starters cultures for production of flavor compounds in cachaça fermentations

In this work, we have used classical genetics techniques to find improved starter strains to produce cachaça with superior sensorial quality. Our strategy included the selection of yeast strains resistant to 5,5',5″-trifluor-D: ,L: -leucine (TLF) and cerulenin, since these strains produce higher levels of higher alcohols and esters than parental strains. However, no clear relationship was observed when levels of flavoring compounds were compared with the levels expression of the genes (BAT1, BAT2, ATF2, EEB1 genes) involved with the biosynthesis of flavoring compounds. Furthermore, we determined the stability of phenotypes considered as the best indicators of the quality of the cachaça for a parental strain and its segregants. By applying the principal component analysis, a cluster of segregants, showing a high number of characteristics similar to the parental strain, was recognized. One segregant, that was resistant to TLF and cerulenin, also showed growth stability after six consecutive replications on plates containing high concentrations of sugar and ethanol. "Cachaça" produced at laboratory scale using a parental strain and this segregant showed a higher level of flavoring compounds. Both strains predominated in an open fermentative process through seven cycles, as was shown by mitochondrial restriction fragment length polymorphisms analysis. Based on the physical chemical composition of the obtained products, the results demonstrate the usefulness of the developed strategies for the selection of yeast strains to be used as starters in "cachaça" production.

Biochemical and molecular characterization of Saccharomyces cerevisiae strains obtained from sugar-cane juice fermentations and their impact in cachaça production

Saccharomyces cerevisiae strains from different regions of Minas Gerais, Brazil, were isolated and characterized aiming at the selection of starter yeasts to be used in the production of cachaça, the Brazilian sugar cane spirit. The methodology established took into account the screening for biochemical traits desirable in a yeast cachaça producer, such as no H2S production, high tolerance to ethanol and high temperatures, high fermentative capacity, and the abilities to flocculate and to produce mycocins. Furthermore, the yeasts were exposed to drugs such as 5,5',5"-trifluor-D,L-leucine and cerulenin to isolate those that potentially overproduce higher alcohols and esters. The utilization of a random amplified polymorphic DNA-PCR method with primers based on intron splicing sites flanking regions of the COX1 gene, as well as microsatellite analysis, was not sufficient to achieve good differentiation among selected strains. In contrast, karyotype analysis allowed a clear distinction among all strains. Two selected strains were experimentally evaluated as cachaça producers. The results suggest that the selection of strains as fermentation starters requires the combined use of biochemical and molecular criteria to ensure the isolation and identification of strains with potential characteristics to produce cachaça with a higher quality standard.