Kombucha is a fermented tea beverage containing live microorganisms, mostly beneficial strains of yeast and acetic acid bacteria (AAB), but empirical evidence is limited supporting the probiotic ...potential of kombucha. This study reports the in vitro probiotic potential of 36 AAB strains isolated from three Kombucha samples commercially available in New Zealand. Nine representative AAB strains, belonging to three species (Komagataeibacter rhaeticus, Acetobacter musti and Gluconobacter potus), were examined for their primary probiotic characteristics such as tolerance to bile salts, NaCl, and low pH, and temperature. Three non-cellulose forming strains (A. musti LOAAB1, G. potus LOAAB2 and G. potus GBAAB3) were assayed for their cell surface characteristics such as auto-aggregation, co-aggregation with pathogenic bacteria, and hydrophobicity. Antimicrobial, antioxidant activities and enzymatic activities were also investigated for the strains of interest. Results indicated that nine strains were able to grow under low pH in the presence of bile salts, suggesting their potential to survive in the human gut. Six K. rhaeticus strains produced cellulosic pellicles, a potential source of prebiotics for beneficial bacteria. The three AAB strains LOAAB1, LOAAB2 and GBAAB3 showed promising cell surface characteristics, such as auto-aggregation rates (>80 %), co-aggregation with four pathogenic bacteria (13.24–43.47 %), hydrophobicity (42.12 % to 50.20 %), and antioxidant activities (>90 %). All nine strains tested negative for enzymatic activities (haemolytic, proteolytic, phospholipase, and gelatinase), suggesting that they are safe to consume. Together, these data indicate the potential for the three AAB strains to be further investigated as probiotic sources with more in vivo tests for applications in the food and beverages industry.
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•Nine acetic acid bacteria isolated from kombucha were evaluated for their in vitro probiotic potential.•Six cellulose forming Komagataeibacter rhaeticus strains exhibited potential prebiotic activities.•Acetobacter musti LOAAB1 and Gluconobacter potus LOAAB2 and GBAAB3 were identified as potential probiotic strains for functional food production.
Sourdough production is an ancient method to ferment flour from cereals for the manufacturing of baked goods. This review deals with the state-of-the-art of current fermentation strategies for ...sourdough production and the microbial ecology of mature sourdoughs, with a particular focus on the use of non-flour ingredients. Flour fermentation processes for sourdough production are typically carried out by heterogeneous communities of lactic acid bacteria and yeasts. Acetic acid bacteria may also occur, although their presence and role in sourdough production can be criticized. Based on the inoculum used, sourdough productions can be distinguished in fermentation processes using backslopping procedures, originating from a spontaneously fermented flour-water mixture (Type 1), starter culture-initiated fermentation processes (Type 2), and starter culture-initiated fermentation processes that are followed by backslopping (Type 3). In traditional recipes for the initiation and/or propagation of Type 1 sourdough productions, non-flour ingredients are often added to the flour-water mixture. These ingredients may be the source of an additional microbial inoculum and/or serve as (co-)substrates for fermentation. An example of the former is the addition of yoghurt; an example of the latter is the use of fruit juices. The survival of microorganisms transferred from the ingredients to the fermenting flour-water mixture depends on the competitiveness toward particular strains of the microbial species present under the harsh conditions of the sourdough ecosystem. Their survival and growth is also determined by the presence of the appropriate substrates, whether or not carried over by the ingredients added.
Acetic acid is an organic acid of great importance globally and the demand of this product is currently increasing. The production of this acid has consequently aroused more and more interest over ...the years, especially for more sustainable processes. From a biological point of view, acetic acid can be produced by acetogenesis using inorganic substrates like CO2 or CO (with acetogenic bacteria) and aerobic fermentation (with acetic acid bacteria or fungi). With the aim of investigating the progress of technological innovation, the methodology applied by this review was an analysis of the international patents with the Espacenet platform, which ensured a worldwide invention overview. Another criterion was the selection of a precise period of time, from 1990 to 2020. A patent review is able to create an overview of the inventions designed for the real scale implementation, providing a whole picture of the state of the art of the technological innovation change. In addition, the most representative works of literature, that consider the influence of operating conditions (T, pH, oxygenation), have been analysed for each process. The present review, with an innovative approach focused on the technological innovation change, highlighted the ongoing interest for acetic acid bioproduction by acetogenic and acetic acid bacteria. The number of patents related to acetic acid bacteria was consistent also in the past years, but recently the interest is moving forward the utilization of genetic engineering (36% of the patents) and new substrates, like agriculture waste (26% of the patens), responding to circular economy principles. On the other hand, the acetic acid production by acetogenic bacteria is most recent, with over the 90% of the patents developed in the last 10 years. In this case the interest is mainly focused on the use of synthesis gas as substrate, that could increase the process sustainability.
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•Biological production of acetic acid is a driver towards sustainability.•The technological innovation in acetic acid production is increasing over the years.•Genetic engineering techniques can enhance acetic acid production.•Alternative carbon sources can decrease the acetic acid production costs.•Yeasts can directly produce acetic acid, but the concentrations are low.
Kombucha consumption has become popular due to health benefits and sensorial properties. Different analytical techniques were associated with unsupervised chemometrics to evaluate kombucha ...fermentation using a low-level data fusion strategy. Kombucha was prepared from green and black teas (Camellia sinensis). The samples were analyzed by ultra-performance liquid chromatography (UPLC), portable near-infrared spectroscopy (NIR), and physicochemical analyses (ethanol, pH, total reducing sugars, and total titratable acidity). Also, the bioactive phenolic compounds were evaluated in the fermented samples. The merged results were analyzed by principal component analysis (PCA). The PCA was applied to discriminate substrate for kombucha production and the fermentation time. Although the fermentation behavior was similar for both substrates, the kombucha showed quantitative differences in physicochemical parameters. They also showed differences in bioactive compounds for each kombucha. Data fusion strategy was more effective to differentiate the two types of kombucha than single analysis. The portable NIR can be a reliable and robust analysis for fermentation monitoring. Moreover, the results can be used as a base to further studies and mainly to help in which substrate composition is better to be produced on an industrial scale.
•Kombuchas were assessed by UPLC, NIR spectroscopy and physicochemical analyses.•A low-level data fusion approach with classical chemometrics was investigated.•Different kombuchas behaved similarly during fermentation.•Data fusion and chemometrics were effective in assessing kombucha fermentation.
ABSTRACT
Cured cocoa beans are obtained through a post-harvest, batchwise process of fermentation and drying carried out on farms in the equatorial zone. Fermentation of cocoa pulp-bean mass is ...performed mainly in heaps or boxes. It is made possible by a succession of yeast, lactic acid bacteria (LAB) and acetic acid bacteria (AAB) activities. Yeasts ferment the glucose of the cocoa pulp into ethanol, perform pectinolysis and produce flavour compounds, such as (higher) alcohols, aldehydes, organic acids and esters. LAB ferment the glucose, fructose and citric acid of the cocoa pulp into lactic acid, acetic acid, mannitol and pyruvate, generate a microbiologically stable fermentation environment, provide lactate as carbon source for the indispensable growth of AAB, and contribute to the cocoa and chocolate flavours by the production of sugar alcohols, organic acids, (higher) alcohols and aldehydes. AAB oxidize the ethanol into acetic acid, which penetrates into the bean cotyledons to prevent seed germination. Destruction of the subcellular seed structure in turn initiates enzymatic and non-enzymatic conversions inside the cocoa beans, which provides the necessary colour and flavour precursor molecules (hydrophilic peptides, hydrophobic amino acids and reducing sugars) for later roasting of the cured cocoa beans, the first step of the chocolate-making.
Yeasts, lactic acid bacteria and acetic acid bacteria enable pulp removal and cocoa bean curing during cocoa fermentation and drying processes, which precede roasting of the cured cocoa beans, the starting material for the production of chocolate.
Temperature and time have an important role in every fermentation process. The present study aimed to explore the effect of both temperature and time on the dynamic changes induced during ...fermentation on the properties of laver kombucha. Laver extracts were obtained by ultrasound-assisted extraction, and fermentation with kombucha scoby was performed at 25 and 30 °C (K-25 and K-30) for 22 days. Higher temperature promoted a faster rate of fermentation as evidenced by the lower pH, higher titratable acidity, and biofilm yield, as well as greater counts of mesophilic, and acetic acid bacteria noted in the product with lower counts of total yeast and amino acids at the end of the fermentation. Samples at a lower temperature (K-25) exhibited higher amounts of bioactive components and greater α-amylase inhibitory activity (92% in the K-25 samples vs. 83% in the K-30 samples at 14 d). In turn, longer fermentation was found to further enhance acid accumulation, showing higher acidity and lower pH, while the amount of bioactive components was reduced. These findings provide a better understanding of the dynamic changes in the characteristics of the newly developed laver kombucha based on the regulation of its fermentation conditions.
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•Impact of temperature and time on characteristics of laver-kombucha was studied.•Higher temperature showed the faster fermentation rate with accumulation of acid.•Longer fermentation time leads to higher acidity and lower bioactive components.
Kefir is a homemade viscous and slightly effervescent beverage obtained by milk fermentation with kefir grains, which are built up by a complex community of lactic acid and acetic acid bacteria and ...yeasts confined in a matrix of proteins and polysaccharides. The present review summarizes the role of kefir micro‐organisms in grain assembly and in the beneficial properties attributed to kefir. The use of both culture‐dependent and independent methods has made possible to determine the micro‐organisms that constitute this ecosystem. Kefir consumption has been associated with a wide range of functional and probiotic properties that could be attributed to the micro‐organisms present in kefir and/or to the metabolites synthetized by them during milk fermentation. In this context, the role of micro‐organisms in kefir health promoting properties is discussed with particular attention to the contribution of yeast as well as bioactive metabolites such as lactic and acetic acid, exopolysaccharides and bioactive peptides. Even though many advances on the knowledge of this ancient fermented milk have been made, further studies are necessary to elucidate the complex nature of the kefir ecosystem.
Kombucha Tea Fermentation: A Review Laureys, David; Britton, Scott J.; De Clippeleer, Jessika
Journal of the American Society of Brewing Chemists,
20/7/2/, Letnik:
78, Številka:
3
Journal Article
Recenzirano
Kombucha tea is made by aerobically fermenting a sweetened tea infusion with a kombucha culture, a symbiotic culture of bacteria and yeasts. The resulting beverage is usually non-alcoholic, sour and ...refreshing, but not naturally sparkling. Many consumers are drinking kombucha because of its alleged health effects and as kombucha tea is increasing in popularity, consumers are increasingly demanding kombucha beverages of better quality. To better adapt their products to these consumer demands, brewers are looking to the scientific knowledge about kombucha for answers. However, the scientific exploration of this complex naturally fermented beverage is still limited. This review paper presents the current state-of-the-art. To further deepen the understanding of the kombucha fermentation process and to help brewers in their search for higher-quality beverages, the microbial species diversity and its dynamics during the fermentation process should be investigated in detail, as well as the kinetics of the substrate consumption and metabolite production, and the relationship between the substrate and metabolite concentrations, and the consumer preferences for the resulting beverage.
Acetic acid bacteria (AAB) are a group of bacteria that can oxidize many substrates such as alcohols and sugar alcohols and play important roles in industrial biotechnology. A majority of industrial ...processes that involve AAB are related to their dehydrogenases, including PQQ/FAD-dependent membrane-bound dehydrogenases and NAD(P)+-dependent cytoplasmic dehydrogenases. These cofactor-dependent dehydrogenases must effectively regenerate their cofactors in order to function continuously. For PQQ, FAD and NAD(P)+ alike, regeneration is directly or indirectly related to the electron transport chain (ETC) of AAB, which plays an important role in energy generation for aerobic cell growth. Furthermore, in changeable natural habitats, ETC components of AAB can be regulated so that the bacteria survive in different environments. Herein, the progressive cascade in an application of AAB, including key dehydrogenases involved in the application, regeneration of dehydrogenase cofactors, ETC coupling with cofactor regeneration and ETC regulation, is systematically reviewed and discussed. As they have great application value, a deep understanding of the mechanisms through which AAB function will not only promote their utilization and development but also provide a reference for engineering of other industrial strains.
Summary
Cocoa bean fermentation is still a spontaneous curing process to facilitate drying of nongerminating cocoa beans by pulp removal as well as to stimulate colour and flavour development of ...fermented dry cocoa beans. As it is carried out on farm, cocoa bean fermentation is subjected to various agricultural and operational practices and hence fermented dry cocoa beans of variable quality are obtained. Spontaneous cocoa bean fermentations carried out with care for approximate four days are characterized by a succession of particular microbial activities of three groups of micro‐organisms, namely yeasts, lactic acid bacteria (LAB) and acetic acid bacteria (AAB), which results in well‐fermented fully brown cocoa beans. This has been shown through a plethora of studies, often using a multiphasic experimental approach. Selected strains of several of the prevailing microbial species have been tested in appropriate cocoa pulp simulation media to unravel their functional roles and interactions as well as in small plastic vessels containing fresh cocoa pulp‐bean mass to evaluate their capacity to dominate the cocoa bean fermentation process. Various starter cultures have been proposed for successful fermentation, encompassing both cocoa‐derived and cocoa nonspecific strains of (hybrid) yeasts, LAB and AAB, some of which have been implemented on farms successfully.
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