Optimization of Culture Medium for the Growth of Candida sp. and Blastobotrys sp. as Starter Culture in Fermentation of Cocoa Beans (Theobroma cacao) Using Response Surface Methodology (RSM)

Candida Species (Volatile) Metabotyping through Advanced Comprehensive Two-Dimensional Gas Chromatography

Microbial metabolomics is a challenge strategy that allows a comprehensive analysis of metabolites within a microorganism and may support a new approach in microbial research, including the microbial diagnosis. Thus, the aim of this research was to in-depth explore a metabolomics strategy based on the use of an advanced multidimensional gas chromatography for the comprehensive mapping of cellular metabolites of C. albicans and non-C. albicans (C. glabrata and C. tropicalis) and therefore contributing for the development of a comprehensive platform for fungal detection management and for species distinction in early growth times (6 h). The volatile fraction comprises 126 putatively identified metabolites distributed over several chemical families: acids, alcohols, aldehydes, hydrocarbons, esters, ketones, monoterpenic and sesquiterpenic compounds, norisoprenoids, phenols and sulphur compounds. These metabolites may be related with different metabolic pathways, such as amino acid metabolism and biosynthesis, fatty acids metabolism, aromatic compounds degradation, mono and sesquiterpenoid synthesis and carotenoid cleavage. These results represent an enlargement of ca. 70% of metabolites not previously reported for C. albicans, 91% for C. glabrata and 90% for C. tropicalis. This study represents the most detailed study about Candida species exometabolome, allowing a metabolomic signature of each species, which signifies an improvement towards the construction of a Candida metabolomics platform whose application in clinical diagnostics can be crucial to guide therapeutic interventions.

Direct Writing of Tunable Living Inks for Bioprocess Intensification

Critical to the success of three-dimensional (3D) printing of living materials with high performance is the development of new ink materials and 3D geometries that favor long-term cell functionality. Here we report the use of freeze-dried live cells as the solid filler to enable a new living material system for direct ink writing of catalytically active microorganisms with tunable densities and various self-supporting porous 3D geometries. Baker's yeast was used as an exemplary live whole-cell biocatalyst, and the printed structures displayed high resolution, large scale, high catalytic activity and long-term viability. An unprecedented high cell loading was achieved, and cell inks showed unique thixotropic behavior. In the presence of glucose, printed bioscaffolds exhibited increased ethanol production compared to bulk counterparts due largely to improved mass transfer through engineered porous structures. The new living materials developed in this work could serve as a versatile platform for process intensification of an array of bioconversion processes utilizing diverse microbial biocatalysts for production of high-value products or bioremediation applications.

Microbial Ecology of Fermented Vegetables and Non-Alcoholic Drinks and Current Knowledge on Their Impact on Human Health

Fermented foods are currently experiencing a re-discovery, largely driven by numerous health benefits claims. While fermented dairy, beer, and wine (and other alcoholic fermented beverages) have been the subject of intensive research, other plant-based fermented foods that are in some case widely consumed (kimchi/sauerkraut, pickles, kombucha) have received less scientific attention. In this chapter, the current knowledge on the microbiology and potential health benefits of such plant-based fermented foods are presented. Kimchi is the most studied, characterized by primarily acidic fermentation by lactic acid bacteria. Anti-obesity and anti-hypertension properties have been reported for kimchi and other pickled vegetables. Kombucha is the most popular non-alcoholic fermented drink. Kombucha's microbiology is remarkable as it involves all fermenters described in known fermented foods: lactic acid bacteria, acetic acid bacteria, fungi, and yeasts. While kombucha is often hyped as a "super-food," only antioxidant and antimicrobial properties toward foodborne pathogens are well established; and it is unknown if these properties incur beneficial impact, even in vitro or in animal models. The mode of action that has been studied and demonstrated the most is the probiotic one. However, it can be expected that fermentation metabolites may be prebiotic, or influence host health directly. To conclude, plant-based fermented foods and drinks are usually safe products; few negative reports can be found, but more research, especially human dietary intervention studies, are warranted to substantiate any health claim.

Effect of pH and Temperature on <I>Bacillus subtilis</I> FNCC 0059 Oxalate Decarboxylase Activity

BACKGROUND AND OBJECTIVE

Bacillus subtilis is a bacterium that can produce the oxalate decarboxylase (ODC) enzyme. This enzyme decomposes oxalate. ODC enzyme activity is influenced by temperature and pH. This study was conducted to determine the optimum pH and temperature for ODC enzyme activity in B. subtilis FNCC 0059.

MATERIALS AND METHODS

B. subtilis was cultivated in oxalate medium at different incubation temperatures for 24 h. The tested temperatures were 25, 29, 33, 37, 41 and 45°C. In separate experiments, cultures were grown in oxalate medium at varying pH from 4-8.5. The cell growth assay and enzyme activity were performed and all the experiments were done with 3 replicates. Data were analyzed using one-way analysis of variance.

RESULTS

The optimum temperature of 37°C could produce maximum ODC enzyme activity (0.041 U mL-1) enzyme activity increased to the point of the optimum pH and then decreased 5.6% when the pH was increased 0.5 from the optimum. Maximum ODC enzyme activity (0.0413 U mL-1) was achieved at pH 5.5.

CONCLUSION

Temperature and the pH of the medium affected ODC enzyme activity. Optimum medium condition of B. subtilis was reached at 37°C and pH 5.5.