Improving SCOBY starter using co-culture of tapai and bakery yeast

Urbahillah A, Jayus J, Nurhayati N. 2021. Improving SCOBY starter using co-culture of tapai and bakery yeast. Biodiversitas 22: 4617-4624. Kombucha is a beverage fermented by a symbiotic bacteria and yeast known as SCOBY (Symbiotic Culture of Bacteria and Yeast). Bacteria and yeast contribute to the formation of organic acids, aroma, taste, and flavor of kombucha. The commercial yeasts used in Indonesian are baker’s yeast and tapai yeast. This study was conducted to develop SCOBYco-culture with tapai yeast and baker’s yeast and evaluate its activity. The ingredients for the kombucha were cascara, water, and sugar, which were fermented with three formula starter, i.e. original SCOBY 10% w/v (SN), co-culture SCOBY 10% w/v with 0.1% w/v of baker’s yeast (SNR), and co-culture SCOBY 10% w/v with tapai yeast 0.1% w/v (SNT). The starter activity were determined based on the OD (Optical Density) value. Yeast screening was carried out on the dominant starter population. Furthermore, morphologically yeast was identified based on colony type, color, and shape of cell. Then yeast was identified by their fermentation profile using API 20C Aux Kit. Isolate A showed white colony with convex elevation and the cell was round-shaped. Colony of isolate B and isolate C were creamy in color and oval cell shaped. The API results revealed that the first isolate was identified as Candida famata, second isolate was as Candida krusei, and the third isolate was as Candida magnoliae. Three types of fungi were found from SCOBY, namely Mucor sp., Trichoderma sp., and Fusarium sp. Mucor sp. has non-septate hyphae, and round black spores. Trichoderma sp. has septate hyphae, greenish-white spores, and the conidia have the shape of globose to ellipsoidal Fusarium sp. has a mold with septate hyphae, yellowish-white colonies, and the conidia have the shape of obovoid. Bacteria, yeast, and mold present in the medium form a powerful symbiosis for produce metabolite.

ECOLOGIZATION OF JOINT PRODUCTION OF ALCOHOL AND BAKERY YEAST FROM MOLASSES

Background. The disadvantage of the two-product technology of alcohol and baker’s yeast from molasses is the need to limit the concentration of dry matter of the source medium to 22% and, accordingly, the level of alcohol accumulation in mature malt not more than 8.0% vol. to prevent deterioration of baker’s yeast. The consequence of this is the high specific cost of steam for bragorectification and increase the specific yield of post-alcohol molasses bard in comparison with single-product technology (obtaining only alcohol). Materials and methods. Raw materials, intermediates and final products were analyzed according to the methods adopted in science and practice of molasses alcohol technology. The dry matter content; pH of the medium; the content of alcohol in the brew, yeast biomass and unfermented sugars; the lifting power of yeast and their color in the resulting products were determined. Results. The possibility of reducing the volume of post-alcoholic molasses bard by returning it for the preparation of molasses bard without deteriorating the quality of baker’s yeast and alcohol yield, as well as by increasing the dry matter concentration of fermented wort from 22 (traditional technology) to 27% and accumulation of alcohol in mature brew up to 10–11% vol. has been experimentally proven. Conclusion. The presented research results provide grounds for the development of energy-saving low-waste two-stage technology of alcohol and baking yeast from mo­lasses, which can be used to obtain high-quality baking yeast to increase the con­centration of alcohol in mature malt by more than 10% vol. This will significantly reduce the steam for bragorectification of alcohol and the volume of contaminated and difficult to dispose of production waste – post-alcohol molasses bard. The implementation of such technology will be the next step in the greening of the joint production of alcohol and baker’s yeast from molasses.

Genome-Assisted Characterization of Lactobacillus fermentum, Weissella cibaria, and Weissella confusa Strains Isolated from Sorghum as Starters for Sourdough Fermentation

Sourdough fermentation of bakery products is a well-established and widespread technique to confer an added value to the resulting food. In recent decades, gluten-free raw materials have gained more attention due to the diffusion of food disorders such as coeliac disease, but, at the same time, they present difficult manipulation and scarce technological properties because of the absence of gluten. For this reason, the present work was aimed at selecting starter cultures for sourdough application that are isolated from fermentation of sorghum flour. Three isolates of Lactobacillus fermentum, Weissella cibaria, and Weissella confusa were selected for the following properties: exopolysaccharide synthesis, acidification, CO2 production, and amylase activity. The investigated phenotypic characteristics were confirmed by genomic analyses, which also highlighted other potentially beneficial features for use in bakery products employment. These strains, together with bakery yeast, were used for bread preparation using sorghum and wheat flour and after 24 h of fermentation the resulting dough was analyzed to assess the improvement of its characteristics. The presence of lactic acid bacteria (LAB) had a great impact on the final dough, and the best preparation, from a rheological point of view, resulted in one made of sorghum and wheat flour with added LAB and bakery yeast, whose resulting characteristics were similar to all wheat flour doughs. The results of this study suggest a potential application of the selected starters in sorghum composite bread and should be validated with data from large-scale pilot tests conducted in industrial bakeries.

THE INFLUENCE OF NANOPARTICLES OF BIOGENIC METALS ON CULTURING THE YEAST SACCHAROMYCES СEREVISIAE

The effect of nanoparticles of biogenic metals (Fe, Mg, Zn, Mn) and their combinations on culturing the yeast Saccharomyces cerevisiae and on fermentation of sugar-containing raw materials into ethanol have been investigated . The research involved the use of nanometal preparations obtained by volumetric electric-spark dispersion. It has proved effective to add nanozinc and a preparation containing nanomanganese and nanomagnesium, prior to yeast cultivation, to the growth media agar and wort agar in the concentrations 0.5 μg/cm3 and 11 μg/cm3 respectively. The experimental yeast grown on the medium containing these preparations increased the alcohol concentration in the distiller’s wort by 0.2%, whereas the content of unfermented carbohydrates remained within the prescribed limits 0.32–0.39 g/100 сm3. The yeast biomass increased by 1.2–1.4 times. Zinc and manganese/magnesium nanopreparations increased the maltase and invertase activities of the yeast under study by 40–25%. The nanoiron preparation contributed to inhibiting the fermentation activity of the yeast biomass. Biogenic metal nanocomplexes are used by yeast as an additional nutrient source. They form organometallic and intracomplex active compounds with yeast cell enzymes, primarily with hexokinase, aldolase, enolase. This intensifies synthesis of enzymes and increases their catalytic effect. The results obtained prove the effectiveness of biogenic metal nanopreparations as catalysts for biochemical transformations in a yeast cell. Using nanometals increases the productivity of bakery yeast, improves the technological process of alcoholic fermentation, and offers ample opportunity to increase the activity of enzyme preparations in the course of their production.

Evidence for two main domestication trajectories in Saccharomyces cerevisiae linked to distinct bread-making processes

SummaryDespite bread being one of the most historically and culturally important fermented products, its history and influence on the evolution of associated microbial species remains largely unknown. The first evidence of leavened bread dates to the second millenium BCE in Egypt and since, the art of bread-making developed and spread worldwide. Nowadays, leavened bread is made either by using a pure commercial culture of the yeast Saccharomyces cerevisiae or by propagating a sourdough, which is a mix of flour and water spontaneously fermented by yeast and bacteria. We studied the domestication of S. cerevisiae populations originating from industry and sourdough and tested whether these different bread-making processes led to population divergence. We found that the origin of S. cerevisiae bakery strains is polyphyletic with 67 % of strains clustering in two main clades: most commercial strains were tetraploid and clustered with strains having diverse origins, including beer. By contrast, most sourdough strains were diploids and found in a second clade of strains having mosaic genomes and diverse origins including fruits, or clinical and wild environments. When compared to the others, sourdough strains harboured in average a higher copy number of genes involved in maltose utilization, a common sugar produced from dough starch. Overall, a high level of gene flow from multiple contributors was detected. Phenotyping of bakery and non bakery strains further showed that sourdough and industrial bakery populations have undergone human selection for rapidly starting fermentations and for high CO2 production. Interestingly, sourdough strains also showed a better adaptation to a sourdough mimicking environment, suggesting that natural selection occurred as well. In summary, our results revealed that the domestication of bakery yeast populations has been accompanied by dispersion, hybridization and divergent selection through industrial and artisanal bakery processes. In addition, they unveiled for the first time a case of fungus domestication where species divergence occurred through autotetraploidisation.

An improved method of dyeing of bakery yeast according to Gram

Knowledge and practical skills of working with microorganisms are required for mastering the modern level of development of veterinary and biological sciences. Microorganisms are the main objects of biotechnology, molecular biology and genetics, and they constantly accompany human and animals in the environment and cohabit inside the body. Direct acquaintance with them and the development of the principles of microbiological research will not only improve their professional level, but also to acquire knowledge and skills are not superfl uous in everyday life. The microscopic method involves the study of living or killed representatives of the microbial (bacteria, bacilli, clostridiums and plectridia) and yeast (bakery, fruit and vegetable, berry and grape yeast) world in a colored or unpainted state using a binocular light microscope. An improved technique of the famous Danish microbiologist G. K. Gram for coloring bakery’s yeast has been presented in the article. On the basis of laboratory researches it has been shown that the diff erentiated coloring according to Gram can be changed on color scale, depending on dyes. Classically according to Gram used: gentian violet, Lugol solution, fuchsin Pfeiff er (based on carbolic fuchsin), but in our technique instead of gentian violet methylene blue has been used, Lugol solution, instead of fuchsin Pfeiff er took red safranin and additionally in the manufacture of the third drug – diamond green dye. It has been shown that the coloring of microbial or yeast cultures has being achieved through the latter dye. So, for example with methylene blue, microbes or yeast are colored blue, with safranin in red and with diamond green in green.

STUDY OF THE INFLUENCE OF MEALS OF WHEAT AND OAT GERMS AND WILD ROSE FRUITS ON THE FERMENTING MICROFLORA ACTIVITY OF RYE-WHEAT DOUGH

The aim of the research was to study an influence of meals of wheat germs (WGM) and oat germs (OGM) in amount 10…20 %, and also ones of wild rose fruits (WRFM) in amount 2…6 % of the total mass of flour on the fermenting microflora of rye-wheat dough; and also to establish an influence of the experimental supplements on main microbiological processes in it. It has been established, that adding experimental meals favors the activation of bakery yeast. At introducing WGM, OGM and WRFM, its lifting force grows by 16.0–54.0, 6.0–18.0, 10.0–44.0 % respectively, and zymase and maltase activity – by 16.0–53.3, 6.0–17.7 and 11.1–44.0 % and 18.8–55.0, 6.3 31.3 and 7.5–25.0 % respectively. It has been established, that there also takes place the activity increase of lactate bacteria in rye-wheat dough with adding meals of wheat, oat germs and wild rose fruits. It is possible at the expanse of adding an additional nutritive medium with the supplements. Such action of enriching raw materials on the microflora favors intensification of alcoholic and lactate fermentation that is established by data of acid accumulation and gas formation in rye-wheat dough. The counted indices at introducing WGM, OGM, WRFM increase by 39.0, 27.8, 33.9 % and 18.2, 13.6, 16.7 % respectively.

Natural allelic variations ofSaccharomyces cerevisiaeimpact stuck fermentation due to the combined effect of ethanol and temperature; a QTL-mapping study

BackgroundFermentation completion is a major prerequisite in many industrial processes involving the bakery yeastSaccharomyces cerevisiae.Stuck fermentations can be due to the combination of many environmental stresses. Among them high temperature and ethanol content are particularly deleterious especially in bioethanol and red wine production. Although the genetic causes of temperature and/or ethanol tolerance were widely investigated in laboratory conditions, few studies investigated natural genetic variations related to stuck fermentations in high gravity matrixes.ResultsIn this study, three QTLs linked to stuck fermentation in winemaking conditions were identified by using a selective genotyping strategy carried out on a backcrossed population. The precision of mapping allows the identification of two causative genesVHS1andOYE2characterized by stop-codon insertion. The phenotypic effect of these allelic variations was validated by Reciprocal Hemyzygous Assay in high gravity fermentations (>240 g/L of sugar) carried out at high temperatures (>28°C). Phenotypes impacted were related to the late stage of alcoholic fermentation during the stationary growth phase of yeast.ConclusionsThe genes identified are related to molecular functions such as Programed Cell Death, ROS metabolism and respire-fermentative switch and were never related to fermentation efficiency. Our findings open new avenues for better understanding yeast resistance mechanisms involved in high gravity fermentations.

Comparison of Leavening Ability of Kluyveromyces lactis in Different Bread Dough Formulations

The aim of this study was to evaluate the dough proofing activity of Kluyveromyces lactis (ATCC 8585) in different dough formulations and to compare it with the commercial active dry bakery yeast Saccharomyces cerevisiae. Leaving ability of yeasts was tested in lean and rich dough. For both cultures, lean and rich dough mixtures containing 0.3 g of yeast biomass (on dry weight basis) and wheat flour in 15 ml of water was prepared. Rich dough contained also either 2.0 g of sucrose, 2.0 g of lactose or 2.5 g of whey powder. Dough mixtures were incubated at 29°C and volume increase was recorded every 15 min. We determined that Kluyveromyces lactis had higher volume and leavening rates compared to commercial bakery yeast strain in lactose-rich or whey-rich dough. These results demonstrated the potential of Kluyveromyces lactis yeast strain as a suitable culture for whey fortified bread making.