•Rhamnolipid biosynthetic and regulatory pathways.•Optimized strains for rhamnolipids production.•Technological prospection and perspectives.
Rhamnolipids have emerged as a very promising class of ...biosurfactants in the last decades, exhibiting properties of great interest in several industrial applications, and have represented a suitable alternative to chemically-synthesized surfactants. This class of biosurfactants has been extensively studied in recent years, aiming at their large-scale production based on renewable resources, which still require high financial costs. Development of non-pathogenic, high-producing strains has been the focus of a number of studies involving heterologous microbial hosts as platforms. However, the intricate gene regulation network controlling rhamnolipid biosynthesis represents a challenge to metabolic engineering and remains to be further understood and explored. This article provides an overview of the biosynthetic pathways and the main gene regulatory factors involved in rhamnolipid production within Pseudomonas aeruginosa, the prototypal producing species. In addition, we provide a perspective view into the main strategies applied to metabolic engineering and biotechnological production.
Flavor compounds are commonly obtained from chemical synthesis or extracted from plants. These sources have disadvantages, such as racemic mixture generation, more steps to yield the final product, ...low yield, and high cost, making the microbial fermentation an alternative and potential way to obtain flavor compounds. The most important lactone for flavor application is γ-decalactone, which has an aroma of peach and can be obtained by ricinoleic acid biotransformation through yeast peroxisomal beta-oxidation. The aim of this work was to use crude glycerol, a residual biodiesel industry, for the production of bioaroma from two different yeasts. Yarrowia lipolytica CCMA 0357 and Lindnera saturnus CCMA 0243 were grown at different concentrations (10, 20, and 30% w/v) of substrates (castor oil and crude glycerol) for γ-decalactone production. L. saturnus CCMA 0243 produced higher concentration of y-decalactone (5.8 g/L) in crude glycerol, whereas Y. lipolytica CCMA 0357 showed a maximum production in castor oil (3.5 g/L). Crude glycerol showed better results for γ-decalactone production when compared to castor oil. L. saturnus CCMA 0243 has been shown to have a high potential for γ-decalactone production from crude glycerol.
The inability of the yeast
Saccharomyces cerevisiae
to produce ethanol from xylose has hampered the biofuel production from lignocellulosic biomass. However, prior studies reveal that functional ...expression of xylose isomerase (XI) from
Burkholderia cenocepacia
(XylA
Bc
) in
S. cerevisiae
has remarkably improved xylose consumption and ethanol productivity. Yet, little is known about kinetic and structural properties of this enzyme. Hereby, a purified recombinant XylA was assayed in vitro, showing optimal enzyme activity at 37 °C and pH 7.2. The K
m
of XylA for
d
-xylose was at least threefold lower than the K
m
results for any XI published to date (e.g. XylA from
Piromyces
sp.). In addition, oligomerization behavior as a tetramer was observed for XylA in solution. Functional and structural comparative analyses amongst three microbial XIs were further performed as theoretical models, showing that xylose orientation at the active site was highly conserved among the XIs. Mg
2+
ions anchor the sugar and guide its pyranoside oxygen towards a histidine residue present at the active site, allowing an acid–base reaction, linearizing xylose. Electrostatic surface analyses showed that small variations in the net charge distribution and dipole moment could directly affect the way the substrate interacts with the protein, thus altering its kinetic properties. Accordingly, in silico modeling suggested the tetramer may be the major functional form. These analyses and the resulting model promote a better understanding of this protein family and pave the way to further protein engineering and application of XylA in the ethanol industry.
Flavor compounds are commonly obtained from chemical synthesis or extracted from plants. These sources have disadvantages, such as racemic mixture generation, more steps to yield the final product, ...low yield, and high cost, making the microbial fermentation an alternative and potential way to obtain flavor compounds. The most important lactone for flavor application is γ-decalactone, which has an aroma of peach and can be obtained by ricinoleic acid biotransformation through yeast peroxisomal β-oxidation. The aim of this work was to use crude glycerol, a residual biodiesel industry, for the production of bioaroma from two different yeasts. Yarrowia lipolytica CCMA 0357 and Lindnera saturnus CCMA 0243 were grown at different concentrations (10, 20, and 30% w/v) of substrates (castor oil and crude glycerol) for γ-decalactone production. L. saturnus CCMA 0243 produced higher concentration of y-decalactone (5.8 g/L) in crude glycerol, whereas Y. lipolytica CCMA 0357 showed a maximum production in castor oil (3.5 g/L). Crude glycerol showed better results for γ-decalactone production when compared to castor oil. L. saturnus CCMA 0243 has been shown to have a high potential for γ-decalactone production from crude glycerol.
The behavior of G. stearothermophilus and B. cereus during the fermentation of cocoa beans was assessed in this study. Cocoa fermentation trials lasted seven days and were conducted inoculating a ...cocktail of spores of strains from each species (3 log CFU/g) daily. During the fermentation period, samples were collected for enumeration of counts of G. stearothermophilus and B. cereus indigenous fermenting microorganisms, physicochemical analysis (water activity, pH, carbohydrates, and ethanol, organic acids) and volatile compounds. The findings indicated that the counts of spores of G. stearothermophilus and B. cereus during cocoa fermentation might increase in approximately 2–3 log spores/g. Even though, the inoculation of G. stearothermophilus and B. cereus spores on cocoa beans did not affect (p > 0.05) the counts of the indigenous microorganisms responsible for cocoa fermentation, the consumption of carbohydrates, production of ethanol, organic acids and volatile compounds appeared to be affected by the presence of sporeforming bacteria. These findings indicate that a deep understanding of the role of sporeforming bacteria and their metabolome through cocoa fermentation is critical. Thus, bacterial spores contaminating cocoa beans will likely be found after the fermentation and may further represent food safety or food stability issues.
•Cocoa fermentation effects on Geobacillus stearothermophilus and Bacillus cereus.•G. stearothermophilus (GB) and B. cereus (BC) up in 2–3 log spores/g in 7 days.•Inoculation of GB and BC did not affect the behavior of indigenous microorganisms.•Physico-chemical and volatile compounds were affected by the presence of GB and BC.•Revealing the role of GB and BC and their metabolome in cocoa fermentation is urged.
The present study evaluated the application of Limosilactobacillus fermentum IAL 4541 and Wickerhamomyces anomalus IAL 4533 isolated from sourdoughs and their combinations, for bio-conservative ...action in panettones, as well as to identify the antifungal volatile compounds. Samples from different fermentation steps were submitted to physicochemical and microbiological evaluation, as to know: sourdough after 48 h (A), 96 h (B), and 144 h (C); dough of the first fermentation (D); final dough after second fermentation (E), and baked panettone (F). In all treatments, lactic bacteria and yeast counts demonstrated a mechanism of proto-cooperation. Panettones containing L. fermentum or W. anomalus in their composition had longer shelf life, which indicates their effect as potential biopreservatives. The genetic sequencing data demonstrated the dominance of the Lactobacilli throughout the process, corroborating the data obtained by cultivable methods. A total of 59 volatile organic compounds were found in this study, and a hierarchical cluster analysis presented the separation between the production stages (C, E) and the most recurrent compounds in the final product (F). Of these compounds, the following stood out (n = 26): acids (7.7%), alcohols (23.1%), aldehydes and ketones (34.6%), and esters (34.6%). The treatments containing L. fermentum presented more diversity of volatile organic compounds with potential antifungal effect. There was a higher production of acetic (1.17–8.85 mmol/kg), phenyllactic (5–10.4 mmol/kg), and propionic (3.5–4.3 mmol/kg) acids in the final product. This study demonstrates the feasibility of applying endogenous starter cultures from sourdoughs, with great biopreservative activity, enabling the production of healthier and more natural panettones.
•Lactobacilli dominated all the steps of all panettone fermentations.•Panettones produced with L. fermentum or W. anomalus starter had a longer shelf life.•Endogenous starter cultures from sourdoughs have great biopreservative activity.•VOC found allowed separating the production stages and the final product.•The treatments containing L. fermentum presented a higher diversity of flavors.
Although carcinogenesis caused by metals has been intensively investigated, the mechanisms of action, especially at the molecular level, are still unclear. This work aimed to investigate Cd(2+), ...Cu(2+), Ni(2+), Cr(3+), and Zn(2+) mutagenicity and its relationship with oxidative stress. We have applied the Functional Assay for the Separation of Alleles in Yeast (FASAY) with only minor modifications to detect p53 defects caused by metals. In this method, human p53-coding gene (TP53) expressed in Saccharomyces cerevisiae activates transcription of the ADE2 reporter gene. Yeast cells, expressing p53, were exposed to increased concentrations of metals and, then, plated on media supplemented or not with adenine. Yeast colonies containing functional p53 grow independently of adenine supplementation and colonies containing nonfunctional p53 are dependent on this nutrient. Mutations in the TP53 are implicated in the pathogenesis of half of all human tumors. According to our results, Cd(2+) was found to be the most toxic metal and produced the highest oxidative damage to lipids and proteins. At low concentrations (40 μM), this metal decreased viability and completely inhibited cell growth, while higher concentrations were necessary to produce the same toxic effect by Cu(2+), Cr(3+), and Ni(2+). Zn(2+) showed no significant toxicity. Cd(2+) strongly induced damages and altered the function of p53, while Cu(2+), followed by Cr(3+), showed lower percentages of p53-mutant colonies. Our results point towards a relationship between the loss of functional p53 protein and oxidative stress, a mechanism that can be associated with tumor formation induced by heavy metals in mammalian cells. By this adaptation of FASAY developed by us it is possible to easily and rapidly detect mutations caused by metals or other stresses.
Data on heart failure (HF) epidemiology in less developed areas of Brazil are scarce.
Our aim was to determine the HF morbidity and mortality in Paraiba and Brazil and its 10-year trends.
A ...retrospective search was conducted from 2008 to 2017 using the DATASUS database and included patients ≥ 15 years old with a primary diagnosis of HF. Data on in-hospital and population morbidity and mortality were collected and stratified by year, gender and age. Pearson correlation and linear-by-linear association test for trends were calculated, with a level of significance of 5%.
From 2008 to 2017, HF admissions decreased 62% (p = 0.004) in Paraiba and 34% (p = 0.004) in Brazil. The in-hospital mortality rate increased in Paraiba and Brazil 65.1% (p = 0.006) and 30.1% (p = 0.003), respectively, but the absolute in-hospital mortality had a significant decrease only in Paraiba 37.5% (p = 0.013), which was maintained after age stratification, except for groups 15-19, 60-69 and > 80 years. It was observed an increase in the hospital stay 44% (p = 0.004) in Paraiba and 12.3% (p = 0.004) in Brazil. From 2008 to 2015, mortality rate for HF in the population decreased 10.7% (p = 0.047) in Paraiba and 7.7% (p = 0.017) in Brazil.
Although HF mortality rate has been decreasing in Paraiba and Brazil, an increase in the in-hospital mortality rate and length of stay for HF has been observed. Hospital-based clinical studies should be performed to identify the causes for these trends of increase.
![[gamma]-decalactone product...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1082-6068/small "[gamma]-decalactone production by Yarrowia lipolytica and Lindnera saturnus in crude glycerol")
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