Improving the Organoleptic Properties of a Craft Mezcal Beverage by Increasing Fatty Acid Ethyl Ester Contents through ATF1 Expression in an Engineered Kluyveromyces marxianus UMPe-1 Yeast

Participation of Acyl-Coenzyme A Synthetase FadD4 of Pseudomonas aeruginosa PAO1 in Acyclic Terpene/Fatty Acid Assimilation and Virulence by Lipid A Modification

The pathogenic bacterium Pseudomonas aeruginosa possesses high metabolic versatility, with its effectiveness to cause infections likely due to its well-regulated genetic content. P. aeruginosa PAO1 has at least six fadD paralogous genes, which have been implicated in fatty acid (FA) degradation and pathogenicity. In this study, we used mutagenesis and a functional approach in P. aeruginosa PAO1 to determine the roles of the fadD4 gene in acyclic terpene (AT) and FA assimilation and on pathogenicity. The results indicate that fadD4 encodes a terpenoyl-CoA synthetase utilized for AT and FA assimilation. Additionally, mutations in fadD paralogs led to the modification of the quorum-sensing las/rhl systems, as well as the content of virulence factors pyocyanin, biofilm, rhamnolipids, lipopolysaccharides (LPS), and polyhydroxyalkanoates. In a Caenorhabditis elegans in vivo pathogenicity model, culture supernatants from the 24-h-grown fadD4 single mutant increased lethality compared to the PAO1 wild-type (WT) strain; however, the double mutants fadD1/fadD2, fadD1/fadD4, and fadD2/fadD4 and single mutant fadD2 increased worm survival. A correlation analysis indicated an interaction between worm death by the PAO1 strain, the fadD4 mutation, and the virulence factor LPS. Fatty acid methyl ester (FAME) analysis of LPS revealed that a proportion of the LPS and FA on lipid A were modified by the fadD4 mutation, suggesting that FadD4 is also involved in the synthesis/degradation and modification of the lipid A component of LPS. LPS isolated from the fadD4 mutant and double mutants fadD1/fadD4 and fadD2/fadD4 showed a differential behavior to induce an increase in body temperature in rats injected with LPS compared to the WT strain or from the fadD1 and fadD2 mutants. In agreement, LPS isolated from the fadD4 mutant and double mutants fadD1/fadD2 and fadD2/fadD4 increased the induction of IL-8 in rat sera, but IL1-β cytokine levels decreased in the double mutants fadD1/fadD2 and fadD1/fadD4. The results indicate that the fadD genes are implicated in the degree of pathogenicity of P. aeruginosa PAO1 induced by LPS-lipid A, suggesting that FadD4 contributes to the removal of acyl-linked FA from LPS, rendering modification in its immunogenic response associated to Toll-like receptor TLR4. The genetic redundancy of fadD is important for bacterial adaptability and pathogenicity over the host.

Alcoholic beverages from araçá-boi fruit: quantification of antioxidant compounds by NMR ERETIC2

Fermentation is a preservation process responsible for increasing food product shelf life. In this context, alcoholic fermentation can add value to unconventional Amazon fruits, e.g., araçá-boi (Eugenia stipitata). This fruit has various antioxidant phenolic compounds with well-known nutraceutical properties. However, araçá-boi is still underexplored by food industry. This rationale led to investigate the influence of five commercial yeasts (Saccharomyces cerevisiae) and filtration process on chemical composition and antioxidant capacity of araçá-boi beverages. DPPH and Folin Ciocalteu assays were used to determine antioxidant capacity and total phenolic content. Organic compounds' contents were assessed by NMR-ERETIC2. In all beverages, ten compounds [tyrosol, sucrose, fructose, (α/β)-glucose, ethanol, malic, citric, gallic, and succinic acids] were identified and quantified. The highest phenolic concentrations [gallic acid (390.0 µM) and tyrosol (380.0 µM)] were found in Biolievito Bayanus (BBA) beverage. The new BBA beverage was used for investigating filtration process influence on chemical composition and antioxidant responses. Alcoholic content (unfiltered: 13.9°GL and filtered: 12.7°GL), antioxidant responses, and total phenolic contents were influenced by filtration process. The yeast type and unfiltered process were determinant for chemical content and antioxidant capacity of beverages. These results might be useful to private sector and future production and commercialization of araçá-boi beverages.

Study of the Enzymatic Capacity of Kluyveromyces marxianus for the Synthesis of Esters

Recently, biotechnological opportunities have been found in non-Saccharomyces yeasts because they possess metabolic characteristics that lead to the production of compounds of interest. It has been observed that Kluyveromyces marxianus has a great potential in the production of esters, which are aromatic compounds of industrial importance. The genetic bases that govern the synthesis of esters include a large group of enzymes, among which the most important are alcohol acetyl transferases (AATases) and esterases (AEATases), and it is known that some are present in K. marxianus, because it has genetic characteristics like S. cerevisiae. It also has a physiology suitable for biotechnological use since it is the eukaryotic microorganism with the fastest growth rate and has a wide range of thermotolerance with respect to other yeasts. In this work, the enzymatic background of K. marxianus involved in the synthesis of esters is analyzed, based on the sequences reported in the NCBI database.

The isc gene cluster expression ethanol tolerance associated improves its ethanol production by organic acids flux redirection in the ethanologenic Escherichia coli KO11 strain

Fossil fuels consumption impacts the greenhouse gas emissions. Biofuels are considered as alternative renewable energy sources to reduce the fossil fuels dependency. Bioethanol produced by recombinant microorganisms is a widely suggested alternative to increase the yield in fermentation processes. However, ethanol and acetate accumulation under the fermentation process had been described as important stressors for the metabolic capabilities of the microorganisms, stopping the fermentation process and affecting the ethanol yield. Ethanol tolerance is a determining factor in the improvement of fermentative properties of microorganisms; however understanding of ethanol tolerance is limited. The engineered Escherichia coli KO11 strain has been studied in detail and used as an ethanologenic bacteria model. The strain is capable of using glucose and xylose for an efficient ethanol yield. In the current work, the effect of the iron-sulfur cluster (ISC) over-expression in the KO11 strain, on its tolerance and ethanol yield, was evaluated. Fatty acids profiles of membrane phospholipids in the E. coli KO11 were modified under ethanol addition, but not due to the hscA mutation. The hscA mutation provoked a decrease in ethanol tolerance in the Kmp strain when was grown with 2% ethanol, in comparison to KO11 parent strain. Ethanol tolerance was improved in the mutant Kmp complemented with the recombinant isc gene cluster (pJC10 plasmid) from LD₅₀ 2.16% to LD₅₀ 3.8% ethanol. In batch fermentation on 1 L bioreactor using mineral medium with glucose (120 g/L), the KO11 strain showed ethanol production efficiencies of ~ 76.9%, while the hscA mutant (Kmp) ~ 75.4% and the transformed strain Kmp(pJC10) showed ~ 92.4% efficiency. Ethanol amount increase in the engineered Kmp(pJC10) strain was correlated with less organic acids (such as acetate and lactate) production in the fermentation medium (2.3 g/L), compared to that in the KO11 (17.05 g/L) and the Kmp (16.62 g/L). Alcohol dehydrogenase (ADH) activity was increased ~ 350% in the transformed Kmp(pJC10) strain, whereas in the Kmp mutant, the phosphoglycerate kinase (PGK), pyruvate kinase (PYK), and ADH activities were diminished, comparing to KO11. The results suggest that the isc system over-expression in the ethanologenic E. coli KO11 strain, increases ethanol yield mainly by improving ethanol tolerance and ADH activity, and by redirecting the metabolic flux from acetate synthesis to ethanol.