Bioflavoring and beer refermentation

Refermentation and maturation of lambic beer in bottles: a necessary step for gueuze production

The production of gueuze beers through refermentation and maturation of blends of lambic beer in bottles is a way for lambic brewers to cope with the variability among different lambic beer batches. The resulting gueuze beers are more carbonated than lambic beers and are supposed to possess a unique flavor profile that varies over time. To map this refermentation and maturation process for gueuze production, a blend of lambic beers was made and bottled, whereby one of them was produced with the old wheat landrace Zeeuwse Witte. Through the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and high-throughput sequencing of bacterial and fungal amplicons, in combination with metabolite target analysis, new insights into gueuze production were obtained. During the initial stages of refermentation, the conditions in the bottles were similar to those encountered during the maturation phase of lambic beer productions in wooden barrels, which was also reflected microbiologically (presence of Brettanomyces species, Pediococcus damnosus, and Acetobacter lambici) and biochemically (ethanol, higher alcohols, lactic acid, acetic acid, volatile phenolic compounds, and ethyl esters). However, after a few weeks of maturation, a switch from a favorable environment to one with nutrient and dissolved oxygen depletion resulted in several changes. Concerning the microbiology, a sequential prevalence of three lactic acid bacterial species occurred, namely, P. damnosus, Lentilactobacillus buchneri, and Lactobacillus acetotolerans, while the diversity of the yeasts decreased. Concerning the metabolites produced, mainly those of the Brettanomyces yeasts determined the metabolic profiles encountered during later stages of the gueuze production.IMPORTANCEGueuze beers are the result of a refermentation and maturation process of a blend of lambic beers carried out in bottles. These gueuze beers are known to have a long shelf life, and their quality typically varies over time. However, knowledge about gueuze production in bottles is scarce. The present study provided more insights into the varying microbial and metabolite composition of gueuze beers during the first 2 years of this refermentation and maturation process. This will allow gueuze producers to gain more information about the influence of the refermentation and maturation time on their beers. These insights can also be used by gueuze producers to better inform their customers about the quality of young and old gueuze beers.

Microbial production and applications of β-glucosidase-A review

β-Glucosidase exists in all areas of living organisms, and microbial β-glucosidase has become the main source of its production because of its unique physicochemical properties and the advantages of high-yield production by fermentation. With the rise of the green circular economy, the production of enzymes through the fermentation of waste as the substrate has become a popular trend. Lignocellulosic biomass is an easily accessible and sustainable feedstock that exists in nature, and the production of biofuels from lignocellulosic biomass requires the involvement of β-glucosidase. This review proposes ways to improve β-glucosidase yield and catalytic efficiency. Optimization of growth conditions and purification strategies of enzymes can increase enzyme yield, and enzyme immobilization, genetic engineering, protein engineering, and whole-cell catalysis provide solutions to enhance the catalytic efficiency and activity of β-glucosidase. Besides, the diversified industrial applications, challenges and prospects of β-glucosidase are also described.

Exploitation of Selected Sourdough Saccharomyces cerevisiae Strains for the Production of a Craft Raspberry Fruit Beer

Recent interest in the special beer category has encouraged the search for novel brewing materials, including new ingredients and novel yeast strains, in order to differentiate the finished products. The aim of this work was to select non-brewing S. cerevisiae strains for the production of a fruit beer with raspberry. The in vitro tests and the wort fermentations allowed the selection of two sourdough S. cerevisiae strains, showing high maltose and maltotriose consumption, high ethanol production, and high viability. Fruit beers (FB) and control beers (CB) without raspberries were prepared. Fruit addition accelerated sugar consumption (7 days compared to 13 days) and increased ethanol and glycerol production by yeasts. Raspberry addition and the inoculated yeast strongly affected the aroma profile of beers. FB samples showed a higher amount of volatile organic compounds (VOCs); the most represented classes were alcohols, followed by esters and acids. FB inoculated by the selected S. cerevisiae SD12 showed the highest VOCs concentration (507.33 mg/L). Results highlighted the possible application of sourdough yeast strains for the brewing process, which, combined with raspberry addition, can be exploited for the production of beers with enhanced aromatic features and suitable chemical properties.

Generating Flavor Molecules Using Scientific Machine Learning

Flavor is an essential component in the development of numerous products in the market. The increasing consumption of processed and fast food and healthy packaged food has upraised the investment in new flavoring agents and consequently in molecules with flavoring properties. In this context, this work brings up a scientific machine learning (SciML) approach to address this product engineering need. SciML in computational chemistry has opened paths in the compound's property prediction without requiring synthesis. This work proposes a novel framework of deep generative models within this context to design new flavor molecules. Through the analysis and study of the molecules obtained from the generative model training, it was possible to conclude that even though the generative model designs the molecules through random sampling of actions, it can find molecules that are already used in the food industry, not necessarily as a flavoring agent, or in other industrial sectors. Hence, this corroborates the potential of the proposed methodology for the prospecting of molecules to be applied in the flavor industry.

Lachancea thermotolerans, an Innovative Alternative for Sour Beer Production

The interest in and growth of craft beer has led to an intense search for new beers and styles. The revival of traditional styles has sometimes been hampered by the use of microorganisms such as lactic acid bacteria. Therefore, studies on alternative yeasts for the production of this style of beer have increased. In this work and together with previous studies carried out with yeasts isolated from Madrid agriculture (from grapes, must, wine, vineyards and wineries), the capacity of 10 yeast strains, belonging to the genus Lachancea thermotolerans, for the production of sour beer has been determined. For this purpose, different fermentation scale-ups (100 mL, 1 L and 100 L) have been performed and their fermentation capacity, aroma compound production (33 volatile compounds by GC), organoleptic profile (trained tasting panel and consumers), melatonin production (HPLC) and antioxidant capacity have been studied. Beer fermented with yeast strain CLI 1232 showed a balanced acidity with a fruity aromatic profile and honey notes. On the other hand, the beer fermented with strain 1-8B also showed a balanced acidity, but less fruity and citric flavour than CLI 1232 strain. Finally, the yeast strain selected by the consumers (CLI 1232) was used for beer production at industrial scale and the market launch of a sour beer.

Commercial craft beers produced in Uruguay: Volatile profile and physicochemical composition

Even beer being the most consumed alcoholic beverage around the world, there is not enough information generated for craft beers produced in Latin America, for either volatile profiles or physicochemical studies. In this work, the chemical and volatile components of ten commercial Blond Ale and nine Indian Pale Ale (IPA) beers from the Uruguayan market were studied using GC-MS. Principal component analysis applied to the data allowed differentiation among the two groups of samples while the volatile compounds and physicochemical parameters responsible for these differences were identified. The physicochemical properties revealed a great diversity between all beer samples even within the same beer style. The main significant differences were obtained for alcohol, polyphenols, bitterness, colour, and pH. Most Blond Ale beer samples were differentiated from IPA ones by raw fermentation aroma compounds such as 1-pentanol, 1-hexanol, hexanoic and isobutyric acids, 4-vinyl guaiacol, and 5,5-dimethyl-2(5H)-furanone. This is the first work that contributes to the knowledge of Uruguayan craft beers. The study also showed the ability of most of the Uruguayan microbreweries to brew Blond Ale and IPA craft beer styles that meet international standards for physicochemical quality.

New Approaches for the Fermentation of Beer: Non-Saccharomyces Yeasts from Wine

Non-Saccharomyces yeasts represent a very attractive alternative for the production of beers with superior sensory quality since they are able to enhance the flavour of beer. Furthermore, they can produce beers with low ethanol content due to the weak fermentative capacity of a large percentage of non-Saccharomyces species. The objective of this study was to evaluate the ability of 34 non-Saccharomyces yeast strains isolated from Madrilenian agriculture to produce a novel ale beer. The non-Saccharomyces yeast strains were screened at two scales in the laboratory. In the first screening, those with undesirable aromas were discarded and the selected strains were analysed. Thirty-three volatile compounds were analysed by GC, as well as melatonin production by HPLC, for the selected strains. Thirteen strains were then fermented at a higher scale in the laboratory for sensory evaluation. Only yeast strains of the species Schizosaccharomyces pombe and Lachancea thermotolerans were able to complete fermentation. Species such as Torulaspora delbrueckii, Metschnikowia pulcherrima, Wickerhamomyces anomalus, Hanseniaspora vineae, and Hanseniaspora guilliermondii could be used both for production of low ethanol beers and co-fermentation with a Saccharomyces yeast to improve the organoleptic characteristics of the beer. In addition, for these strains, the levels of melatonin obtained were higher than the concentrations found for Saccharomyces strains subjected to the same study conditions. The selected strains can be used in future trials to further determine their viability under different conditions and for different purposes.

Amylolytic Fungi in the Ethnic Beer Starter “emao” and Their Beer-Producing Attributes

Naturally occurring autochthonous microbes associated with ethnic beer starters are diverse and important as they play different functional roles in beer fermentations. The study on culturable microbes from the ethnic rice beer starter “emao” of the Bodo community of Assam is limited. Here we isolated and identified the culturable fungal diversity associated with emao and screened them for beer-producing capability from glucose and starch substrates. Based on morphology and molecular characterization, the species identified were Candida glabrata (Cgla_RF2), Cyberlindnera fabianii (Cfab_RF37), Hyphopichia burtonii (Hbur_RF19), Mucor circinelloides (Mcir_RF48), Mucor indicus (Mind_RF25), Penicillium citrinum (Pcit_RF32), Rhodosporidiobolus ruineniae (Rrui_RF4 & Rrui_RF43), Saccharomyces cerevisiae (Scer_RF6), Saccharomycopsis fibuligera (Sfib_RF11), and Wickerhamomyces anomalus (Wano_RF3) among which the relative abundance (RA) of W. anomalus was the highest (24%) followed by C. glabrata and H. burtonii (16% in each). Five (Hbur_RF19, Sfib_RF11, Mind_RF25, Mcir_RF48, and Pcit_RF32) of eleven isolates showed amylase positive in the starch medium. Scer_RF6 showed the highest ethanol tolerance (14% v/v) followed by Hbur_RF19 (12% v/v), Cgla_RF2 (11% v/v) and Wano_RF3 (11% v/v). The amylase-positive strains produced beer-containing ethanol in the range of 3.17–7.3 (% v/v) from rice substrate. Although the rice beer produced by amylase-positive strains showed negligible pH difference, other parameters like ethanol, ascorbic acid, total phenol, and antioxidant properties were varied from beer to beer. Antibacterial activities shown by Mcir_RF48 and Pcit_RF32 against the test bacteria were higher with a 23–35 mm zone of inhibition than the other isolates. The present findings reveal the presence of fungi with antibacterial, amylolytic, ethanol fermenting, and antioxidant producing capacity in emao which could the source for future bioprospection.

Aroma Clouds of Foods: A Step Forward to Unveil Food Aroma Complexity Using GC × GC

The human senses shape the life in several aspects, namely well-being, socialization, health status, and diet, among others. However, only recently, the understanding of this highly sophisticated sensory neuronal pathway has gained new advances. Also, it is known that each olfactory receptor cell expresses only one type of odorant receptor, and each receptor can detect a limited number of odorant substances. Odorant substances are typically volatile or semi-volatile in nature, exhibit low relative molecular weight, and represent a wide variety of chemical families. These molecules may be released from foods, constituting clouds surrounding them, and are responsible for their aroma properties. A single natural aroma may contain a huge number of volatile components, and some of them are present in trace amounts, which make their study especially difficult. Understanding the components of food aromas has become more important than ever with the transformation of food systems and the increased innovation in the food industry. Two-dimensional gas chromatography and time-of-flight mass spectrometry (GC × GC-ToFMS) seems to be a powerful technique for the analytical coverage of the food aromas. Thus, the main purpose of this review is to critically discuss the potential of the GC × GC–based methodologies, combined with a headspace solvent-free microextraction technique, in tandem with data processing and data analysis, as a useful tool to the analysis of the chemical aroma clouds of foods. Due to the broad and complex nature of the aroma chemistry subject, some concepts and challenges related to the characterization of volatile molecules and the perception of aromas will be presented in advance. All topics covered in this review will be elucidated, as much as possible, with examples reported in recent publications, to make the interpretation of the fascinating world of food aroma chemistry more attractive and perceptive.

Wine Saccharomyces Yeasts for Beer Fermentation

Multiple studies in recent years have shown the potential of Saccharomyces wild yeasts to produce craft beers with new flavour profiles and other desirable properties. Yeasts isolated from food (wine, bread, kombucha…) have shown potential promise for application in brewing. The aim of this study is to evaluate the ability of 141 Saccharomyces yeast strains isolated from the Madrilenian agriculture (from grapes, must, wine, vineyard, and cellars) to produce a novel ale beer. Fermentation activity of the strains was compared against the commercial strain Saccharomyces cerevisiae Safale S-04. In addition to the other aspects such as melatonin production, thirty-three volatile compounds belonging to higher alcohols, esters, aldehydes/cetones, acids, lactones and phenolic groups, were analysed by GC for selection of the strains. Ten strains were finally chosen, among which the most relevant was the strain G 520 showing a higher production of esters, higher alcohols and acids compared with S-04. The apparent attenuation for this strain was lower than commercial strain, which translates into more residual sugars. Furthermore, G 520 was more capable of producing significantly higher amounts of melatonin studied by HPLC, as well as showing a higher antioxidant capacity. Consumer study showed that G 520 strain could be used to produce a potential beer that has a place in the current market.

Technological and Environmental Features Determine the Uniqueness of the Lambic Beer Microbiota and Production Process

Lambic beers are beers produced through spontaneous fermentation and maturation in wooden barrels. The production process of lambic beers differs from the production processes of lagers and ales in process technology, environmental parameters, and the use of specific raw materials. Moreover, every lambic beer production process is unique in terms of microbiology and flavor formation because of its dependence on the spontaneous inoculation of microorganisms coming from the environmental air (contacting the open coolship and other brewery equipment) and the inner surfaces of the barrels. Several factors influence the inter- and intraspecies microbial successions during lambic beer wort fermentation and maturation and determine the final quality of the end products. The possibility to manually acidify the wort, the presence of species-specific metabolic traits, the environmental temperature, the co-occurrence of lactic acid bacteria and acetic acid bacteria, as well as yeasts, and the quality of the wooden barrels all determine the progress and outcome of the lambic beer production process. Further alterations in quality and flavor of lambic beers can be achieved by blending practices and additional bottle refermentations. This results in a vast array of lambic-derived beer products (e.g., gueuze) with complex taste and aroma profiles and specific characteristics, which separate them from most other commercially available beers.

Packing a punch: understanding how flavours are produced in lager fermentations

Beer is one of the most popular beverages in the world and it has an irreplaceable place in culture. Although invented later than ale, lager beers dominate the current market. Many factors relating to the appearance (colour, clarity and foam stability) and sensory characters (flavour, taste and aroma) of beer, and other psychological determinants affect consumers' perception of the product and defines its drinkability. This review takes a wholistic approach to scrutinise flavour generation in the brewing process, focusing particularly on the contribution of the raw ingredients and the yeasts to the final flavour profiles of lager beers. In addition, we examine current developments to improve lager beer flavour profiles for the modern consumers.

A Preliminary Investigation of the Effect of Ethical Labeling and Moral Self-Image on the Expected and Perceived Flavor and Aroma of Beer

Ethical labelling has been shown to influence taste/flavour perception. Across two experiments, the present study examined how ethical labelling and moral self-image influenced both the expected (Experiment One) and perceived (Experiment Two) taste/flavour characteristics of beer. In Experiment One, 170 participants read either a ‘moral’ or ‘control’ label describing a brewery, after which they were presented with an image of a beer. Participants then completed a Beer Taste Perception Questionnaire and the Moral Self-Image Scale. In Experiment Two, 59 participants were exposed to either the moral or control label before tasting a beer and completing the same questionnaires from Experiment One. The results of Experiment One indicated that label type moderated the relationship between moral self-image and the intensity ratings of the beer. Specifically, in the presence of a control label, the expected intensity of the beer’s flavour increased as moral self-image increased. Experiment Two found no evidence that the moral label influenced the perceived taste of the beer. However, the results showed that as moral self-image became more positive the perceived refreshingness of the beer increased. This study provides novel evidence of the potential relationship between an individual’s moral self-image and the expected and perceived taste/flavour characteristics of beer.

[Non-conventional yeasts as tools for innovation and differentiation in brewing]

Yeasts play a crucial role in brewing. During fermentation, besides ethanol and carbon dioxide, yeasts produce a considerable number of organic compounds, which are essential for beer flavor. In particular, Saccharomyces cerevisiae and Saccharomyces pastorianus are traditionally used in the production of ale and lager beers, respectively. Nowadays, the continuous growth of the craft beer market motivates the production of differential and innovative beers; leading specialists and brewers focus on non-conventional yeasts as tools for new product development. In this work, we describe the potential application of non-conventional yeast species such as those of the genera Brettanomyces, Torulaspora, Lachancea, Wickerhamomyces, Pichia and Mrakia in the craft brewing industry, as well as non-traditional brewing yeasts of the Saccharomyces genus. Furthermore, the fermentation conditions of these non-conventional yeasts are discussed, along with their abilities to assimilate and metabolize diverse wort components providing differential characteristics to the final product. In summary, we present a comprehensive review of the state-of-the-art of non-conventional yeasts, which is highly relevant for their application in the production of novel craft beers including flavored beers, non-alcoholic beers, low-calorie beers and functional beers.

Mutagenesis, screening and isolation of Brettanomyces bruxellensis mutants with reduced 4-ethylphenol production

The use of non-conventional yeast species to obtain interesting flavors and aromas has become a new trend in the fermented beverages industry. Among such species, Brettanomyces bruxellensis (B. bruxellensis) has been reported as capable of producing desirable or at least singular aromas in fermented beverages like beer and wine. However, this yeast can also produce an aromatic defect by producing high concentrations of phenolic compounds like, 4-ethylguaiacol and particularly 4-ethylphenol (4-EP). In the present study, we designed a mutant screening method to isolate B. bruxellensis mutants with reduced 4-EP production. More than 1000 mutants were screened with our olfactory screening method, and after further sensory and chemical analysis we were able to select a B. bruxellensis mutant strain with a significant reduction of 4-EP production (more than threefold) and less phenolic perception. Notably, the selected strain also showed higher diversity and concentration of ethyl esters, the most important group of odor active compounds produced by yeasts. Based on these results, we consider that our selected mutant strain is a good candidate to be tested as a non-conventional yeast starter (pure or in co-inoculation) to obtain wines and beers with novel aromatic properties.

Effect of Saccharomyces and non-Saccharomyces native yeasts on beer aroma compounds

Recently, the increase in microbreweries and the consequent production of craft beers have reached exponential growth. The interest in non-conventional yeasts for innovation and a unique selling feature in beer fermentation is increasing. This work studied the autochthonous Saccharomyces and non-Saccharomyces yeasts, isolated from various food sources, with the ability to modify and improve the fermentative and aromatic profiles during alcoholic fermentation. The ability to ferment maltose and produce desirable aroma compounds were considered as the key characters for the screening selection. A synthetic beer wort was developed for this purpose, to simulate beer wort composition. A total of forty-seven yeast strains belonging to different genera were analysed according to their fermentation profile, volatile compounds production and sensory analysis. Three native strains of Saccharomyces cerevisiae, Zygoascus meyerae and Pichia anomala were selected to evaluate their aromatic profile in single and mixed fermentations. The strains produced 4-vinylguaiacol, β-phenylethyl alcohol, and isoamyl alcohol at levels significantly above the sensory threshold, making them interesting for wheat and blond craft beer styles. The native Hanseniaspora vineae was also included in a co-fermentation treatment, resulting in a promising yeast to produce fruity beers.

Bottle Conditioning: Technology and Mechanisms Applied in Refermented Beers

Bottle conditioning refers to a method of adding fermenting wort or yeast suspension in sugar solution into beer in its final package. Additionally denoted as bottle refermentation, this technique has been originally developed to assure beer carbonation, and has further significance related to formation of distinctive sensory attributes and enhancement of sensory stability, which are the phenomena associated with ongoing yeast metabolic activities in the final package. This review covers historical development of the method, describes metabolic pathways applied during refermentation, and explains practical aspects of the refermentation process management. Furthermore, an overview of the traditional and novel approaches of bottle conditioning with mixed yeast bacterial cultures and its impact on the properties of final beer is provided.

Happy Hour? A Preliminary Study of the Effect of Induced Joviality and Sadness on Beer Perception

Our emotions influence our perception. In order to determine whether emotion influences the perception of beer, 32 participants watched either a scene from the movie Wall-E to induce joviality, or a short clip from the Shawshank Redemption to induce sadness. The participants were then required to sample up to 250 mL of Yenda Pale Ale beer and rate it on a variety of taste and flavor characteristics (e.g., bitterness), before completing the Positive and Negative Affect Schedule-X (PANAS-X). The data were analyzed using Bayesian t-tests and Null Hypothesis Significance Tests (NHSTs). After applying conservative corrections for multiple comparisons, NHSTs failed to reach statistical significance. However, the effect sizes suggested that inducing joviality, relative to inducing sadness, resulted in the beer being rated as (a) tasting more pleasant, (b) tasting sweeter, and (c) being of higher quality. Following the induction of joviality, participants were also willing to pay more for the beer. The Bayesian analyses indicated that induced emotion can influence flavor perception for complex taste stimuli. The effect sizes and Bayesian analyses are interpreted in terms of Feelings-as-Information theory. These preliminary findings can tentatively be applied to real-world environments such as venues that serve and/or market alcohol.

Unraveling Brazilian bioethanol yeasts as novel starters for high-gravity brewing

High-gravity (HG) brewing has broader application to succeed on beer differentiation and production optimization. However, such process imposes a handicap to yeasts, which must be able to deal with stressful conditions in fermentation. In this work, we assessed different physiological traits of 24 Saccharomyces cerevisiae strains isolated from Brazilian bioethanol distilleries for the selection of novel starters for HG brewing. Five yeast strains were selected with ability to overcome different stressors under HG beer fermentation, showing high fermentability rates, resilience to ethanol stress, low production of foam and hydrogen sulfide, as well as similar flocculation rates to brewer's yeasts. After five fermentation recycles, most strains sustained a viability rate higher than 90% and were able to efficiently accumulate trehalose and glycogen, besides presenting no detectable petite mutants at the final stage. In the sensory analysis, the beers obtained from the five selected strains showed greater aromatic complexity, with predominance of 'spicy', 'dried' and 'fresh fruits' descriptors. In conclusion, this study sheds light on the potential of yeast strains from Brazilian bioethanol process to produce distinctive specialty beers, aside from proposing an effective selection methodology based on relevant physiological attributes for HG brewing process.

Screening for the Brewing Ability of Different Non-Saccharomyces Yeasts

Non-Saccharomyces yeasts have aroused interest in brewing science as an innovative and seminal way of creating new beer flavors. A screening system for potential brewing strains of non-Saccharomyces yeasts was set up to investigate the yeast’s utilization of wort sugars and to examine the effect of hop acids as well as ethanol on the growth of different yeast strains. Additionally, phenolic off-flavor (POF) and sensory odor tests of fermented wort samples were performed. The promising strains were further investigated for their propagation ability and for following fermentation trials. The produced beers were analyzed for secondary metabolites, ethanol content and judged by trained panelists. Subsequently to the screening, it was discovered that among the 110 screened yeast strains, approx. 10 strains of the species Saccharomycopsis fibuligera, Schizosaccharomyces pombe and Zygosaccharomyces rouxii generate promising fruity flavors during fermentation and were able to metabolize maltose and maltotriose as a prerequisite for the production of alcoholic beers. Consequently, the screening method described in this study makes it possible to investigate a tremendous number of different non-Saccharomyces yeasts and to test their brewing ability in a relatively short period of time.

Exploitation of Three Non-Conventional Yeast Species in the Brewing Process

Consumers require high-quality beers with specific enhanced flavor profiles and non-conventional yeasts could represent a large source of bioflavoring diversity to obtain new beer styles. In this work, we investigated the use of three different non-conventional yeasts belonging to Lachancea thermotolerans, Wickerhamomyces anomalus, and Zygotorulaspora florentina species in pure and mixed fermentation with the Saccharomyces cerevisiae commercial starter US-05. All three non-conventional yeasts were competitive in co-cultures with the S. cerevisiae, and they dominated fermentations with 1:20 ratio (S. cerevisiae/non-conventional yeasts ratios). Pure non-conventional yeasts and co-cultures affected significantly the beer aroma. A general reduction in acetaldehyde content in all mixed fermentations was found. L. thermotolerans and Z. florentina in mixed and W. anomalus in pure cultures increased higher alcohols. L. thermotolerans led to a large reduction in pH value, producing, in pure culture, a large amount of lactic acid (1.83 g/L) while showing an enhancement of ethyl butyrate and ethyl acetate in all pure and mixed fermentations. W. anomalus decreased the main aroma compounds in comparison with the S. cerevisiae but showed a significant increase in ethyl butyrate and ethyl acetate. Beers produced with Z. florentina were characterized by an increase in the isoamyl acetate and α-terpineol content.

Pretreatment optimization of the biomass of Microcystis aeruginosa for efficient bioethanol production

Microalgae are considered to be the future promising sources of biofuels and bio products. The algal carbohydrates can be fermented to bioethanol after pretreatment process. Efficient pretreatment of the biomass is one of the major requirements for commercialization of the algal based biofuels. In present study the microalga, M. aeruginsa was used for pretreatment optimization and bioethanol production. Treatment of algal biomass with CaO before acid and/or enzymatic hydrolysis enhanced the degradation of algal cells. Monomeric sugars yield was increased more than twice when biomass was pretreated with CaO. Similarly, an increase was noted in the amount of fermentable sugars when biomass was subjected to invertase saccharification after acid or lysozyme pretreatment. Highest yield of fermentable sugars (16 mM/ml) in the centrifuged algal juice was obtained. 4 Different microorganisms' species were used individually and in combination for converting centrifuged algal juice to bioethanol. Comparatively higher yield of bioethanol (60 mM/ml) was obtained when the fermenter microorganisms were used in combination. The results demonstrated that M. arginase biomass can be efficiently pretreated to get higher yield of fermentable sugars for enhanced yield of bioethanol production.

Physiology, ecology and industrial applications of aroma formation in yeast

Yeast cells are often employed in industrial fermentation processes for their ability to efficiently convert relatively high concentrations of sugars into ethanol and carbon dioxide. Additionally, fermenting yeast cells produce a wide range of other compounds, including various higher alcohols, carbonyl compounds, phenolic compounds, fatty acid derivatives and sulfur compounds. Interestingly, many of these secondary metabolites are volatile and have pungent aromas that are often vital for product quality. In this review, we summarize the different biochemical pathways underlying aroma production in yeast as well as the relevance of these compounds for industrial applications and the factors that influence their production during fermentation. Additionally, we discuss the different physiological and ecological roles of aroma-active metabolites, including recent findings that point at their role as signaling molecules and attractants for insect vectors.

Microbial Contribution to Wine Aroma and Its Intended Use for Wine Quality Improvement

Wine is a complex matrix that includes components with different chemical natures, the volatile compounds being responsible for wine aroma quality. The microbial ecosystem of grapes and wine, including Saccharomyces and non-Saccharomyces yeasts, as well as lactic acid bacteria, is considered by winemakers and oenologists as a decisive factor influencing wine aroma and consumer's preferences. The challenges and opportunities emanating from the contribution of wine microbiome to the production of high quality wines are astounding. This review focuses on the current knowledge about the impact of microorganisms in wine aroma and flavour, and the biochemical reactions and pathways in which they participate, therefore contributing to both the quality and acceptability of wine. In this context, an overview of genetic and transcriptional studies to explain and interpret these effects is included, and new directions are proposed. It also considers the contribution of human oral microbiota to wine aroma conversion and perception during wine consumption. The potential use of wine yeasts and lactic acid bacteria as biological tools to enhance wine quality and the advent of promising advice allowed by pioneering -omics technologies on wine research are also discussed.

Influence of yeast strain, priming solution and temperature on beer bottle conditioning

BACKGROUND

Recently, there has been a significant increase in the number of microbreweries. Usually, craft beers are bottle conditioned; however, few studies have investigated beer refermentation. One of the objectives of this study was to evaluate the impacts of different experimental conditions, specifically yeast strain, priming solution and temperature, on the standard quality attributes, the volatile compounds and the sensory profile of the bottle-conditioned beer. The other aim was to monitor the evolution of volatile compounds and amino acids consumption throughout the refermentation process to check if it is possible to reduce the time necessary for bottle conditioning.

RESULTS

The results indicate that the volatile profile was mainly influenced by the strain of yeast, and this may have obscured the possible impacts of the other parameters. Our results also confirm that the two yeast strains showed different metabolic activity, particularly with respect to esters production. Moreover, we found the Safbrew S-33® strain when primed with Siromix® and refermented at 30 °C yielded the fastest formation of higher alcohols while maintaining low production of off-flavours.

CONCLUSIONS

These results suggest a formulation that may reduce the time needed for bottle conditioning without affecting the quality of the final beer which may simultaneously improve efficiency and economic profits. © 2016 Society of Chemical Industry.

Enhancing the Feasibility of Microcystis aeruginosa as a Feedstock for Bioethanol Production under the Influence of Various Factors

Microcystis aeruginosa, a freshwater microalga, is capable of producing and accumulating different types of sugars in its biomass which make it a good feedstock for bioethanol production. Present study aims to investigate the effect of different factors increasing growth rate and carbohydrates productivity of M. aeruginosa. MF media (modified BG11 media) and additional ingredients such as aminolevulinic acid (2 mM), lysine (2.28 mM), alanine (1 mM), and Naphthalene acetic acid (1 mM) as cytokine promoted M. aeruginosa growth and sugar contents. Salmonella showed growth-assisting effect on M. aeruginosa. Enhanced growth rate and carbohydrates contents were observed in M. aeruginosa culture grown at 25°C under red LED light of 90 μmolm⁻²s⁻¹ intensity. More greenish and carbohydrates rich M. aeruginosa biomass was prepared (final OD_660 nm = 2.21 and sugar contents 10.39 mM/mL) as compared to control (maximum OD_660 nm = 1.4 and sugar contents 3 mM/mL). The final algae biomass was converted to algae juice through a specific pretreatment method. The resulted algae Juice was used as a substrate in fermentation process. Highest yield of bioethanol (50 mM/mL) was detected when Brettanomyces custersainus, Saccharomyces cerevisiae, and Pichia stipitis were used in combinations for fermentation process as compared to their individual fermentation. The results indicated the influence of different factors on the growth rate and carbohydrates productivity of M. aeruginosa and its feasibility as a feedstock for fermentative ethanol production.

Characterization of the recombinant Brettanomyces anomalus β-glucosidase and its potential for bioflavouring

AIM

Plant materials used in the food industry contain up to five times more aromas bound to glucose (glucosides) than free, unbound aromas, making these bound aromas an unused flavouring potential. The aim of this study was to identify and purify a novel β-glucosidase from Brettanomyces yeasts that are capable of releasing bound aromas present in various food products.

METHODS AND RESULTS

We screened 428 different yeast strains for β-glucosidase activity and are the first to sequence the whole genome of two Brettanomyces yeasts (Brettanomyces anomalus and Brettanomyces bruxellensis) with exceptionally high β-glucosidase activity. Heterologous expression and purification of the identified B. anomalus β-glucosidase showed that it has an optimal activity at a higher pH (5·75) and lower temperature (37°C) than commercial β-glucosidases. Adding this B. anomalus β-glucosidase to cherry beers and forest fruit milks resulted in increased amounts of benzyl alcohol, eugenol, linalool and methyl salicylate compared to Aspergillus niger and Almond glucosidase.

CONCLUSIONS

The newly identified B. anomalus β-glucosidase offers new possibilities for food bioflavouring.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first to sequence the B. anomalus genome and to identify the β-glucosidase-encoding genes of two Brettanomyces species, and reports a new bioflavouring enzyme.

Evaluation of Beer Fermentation with a Novel Yeast Williopsis saturnus

The aim of this study is to evaluate the potential of a novel yeast Williopsis saturnus var. mrakii NCYC 500 to produce fruity beer. Fermentation performance of W. mrakii and beer volatile composition were compared against that fermented with Saccharomyces cerevisiae Safale US-05. ^oBrix, sugar and pH differed significantly between the two types of beer. A total of 8 alcohols, 11 acids, 41 esters, 9 aldehydes, 8 ketones, 21 terpenes and terpenoids, 5 Maillard reaction products and 2 volatile phenolic compounds were detected. Yeast strain Safale US-05 was more capable of producing a wider range of ethyl and other esters, while yeast strain NCYC 500 produced significantly higher amounts of acetate esters. Strain NCYC 500 retained more terpenes and terpenoids, suggesting that the resultant beer could possess more of the aromatic hint of hops. This study showed that W. saturnus var. mrakii NCYC 500 could ferment wort to produce low-alcohol beer with higher levels of acetate esters, terpenes and terpenoids than yeast S. cerevisiae Safale US-05.