Jerusalem artichoke as low-cost fructose-rich feedstock for fossil fuels desulphurization by a fructophilic bacterium.

AIMS: Through biodesulphurization (BDS) is possible to remove the sulphur present in fossil fuels to carry out the very strict legislation. However, this biological process is limited by the cost of the culture medium, and thus, it is important to explore cheaper alternative carbon sources, such as Jerusalem artichoke (JA). These carbon sources usually contain sulphates which interfere with the BDS process. The goal of this work was to remove the sulphates from Jerusalem artichoke juice (JAJ) through BaCl2 precipitation viewing the optimization of dibenzothiophene (DBT) desulphurization by Gordonia alkanivorans strain 1B. METHODS AND RESULTS: Using a statistical design (Doehlert distribution), the effect of BaCl2 concentration (0.125-0.625%) and pH (5-9) was studied on sulphate concentration in hydrolysed JAJ. A validated surface response derived from data indicated that zero sulphates can be achieved with 0.5-0.55% (w/v) BaCl2 at pH 7; however, parallel BDS assays showed that the highest desulphurization was obtained with the juice treated with 0.5% (w/v) BaCl2 at pH 8.73. Further assays demonstrated that enhanced DBT desulphurization was achieved using hydrolysed JAJ treated in these optimal conditions. A total conversion of 400 µmol l(-1) DBT into 2-hydroxybiphenyl (2-HBP) in <90 h was observed, attaining a 2-HBP maximum production rate of 28.2 µmol l(-1) h(-1) and a specific production rate of 5.06 µmol(-1) g(-1) (DCW) h(-1) . CONCLUSIONS: These results highlight the efficacy of the treatment applied to JAJ in making this agromaterial a promising low-cost renewable feedstock for improved BDS by the fructophilic strain 1B. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is a fundamental step viewing BDS application at the industrial level as it accounts a cost-effective production of the biocatalysts, one of the main drawbacks for BDS scale-up.

Environmental dynamics of Bacillus amyloliquefaciens CCMI 1051 antifungal activity under different nitrogen patterns.

AIMS: The aim of this study was to evaluate the influence of environmental conditions on the antifungal activity of the Bacillus sp. CCMI 1053 cultures. METHODS AND RESULTS: The electrospray ionization mass spectra (ESI-MS) analysis was used to detect the active peptides produced by Bacillus amyloliquefaciens CCMI 1051 cultures in a glucose-containing medium to which four different nitrogen sources were added. The cultures produced different patterns of Bacillus sporulation and distinct antifungal activity of the cell-free culture broths. CONCLUSIONS: The highest sporulation obtained corresponds to higher antifungal activity when it is formed after 3 days of microbial growth. The antifungal activity against Trichoderma harzianum CCMI 783 is more influenced by the concentration on the nitrogen source than the culture time of incubation. The association of nitrogen concentration and the time of incubation is particularly relevant in the expression of the antifungal activity. SIGNIFICANCE AND IMPACT OF THE STUDY: The present findings allow the reduction of the use of chemical pesticides and to limit some plant diseases. The association of the nitrogen source and the time of incubation is a novelty, which would improve the production of secondary metabolites. Both economical and environmental benefits arise from the study.

Stimulation of Erwinia sp. fumarase and aspartase synthesis by changing medium components.

The optimal concentrations of nutrient medium components, aeration conditions, and pH providing for maximum biomass yields, as well as fumarase and L-aspartase activities, during submerged cultivation of Erwinia sp. were determined. The data showed that different concentrations of carbon source (molasses) and pH of the nutrient medium were required to reach the maximum fumarase and L-aspartase activities. Calculations performed by application of the additive lattice model suggested that the combination of these optimized factors would result in 3.2-, 3.4-, and 3.8-fold increases as compared to the experimental means in Erwinia sp. biomass, and L-aspartase and fumarase activities, respectively. The conditions of the fumaric acid biotransformations into L-malic and L-aspartic acids were optimized on the basis of intact Erwinia sp. cells, a fumarase and L-aspartase producer. In the cases of fumarate transformation into L-malic acid and of fumarate transformation into L-aspartic acids, fumarase and L-aspartase activities increased 1.5- and 1.7-fold, respectively. The experimental data were consistent with these estimates to 80% accuracy. In comparison with the additive lattice model, the application of polynomial nonlinear model allowed the between-factor relations to be considered and analyzed, which resulted in 1.1-, 1.27-, and 1.1-fold increases in Erwinia sp. biomass and fumarase and L-aspartase activities for the case of cultivation. In the case of fumarate transformation into L-malic acid, this model demonstrated a 1.7-fold increase in fumarase activity, whereas during fumarate transformation into L-aspartic acid no significant change in aspartase activity was observed.

Antimicrobial activity of methyl cis-7-oxo deisopropyldehydroabietate on Botrytis cinerea and Lophodermium seditiosum: ultrastructural observations by transmission electron microscopy.

AIMS: To study the antifungal activity of methyl cis-7-oxo-deisopropyldehydroabietate (MCOD) against phytopathogenic fungi, Botrytis cinerea and Lophodermium seditiousm. The effect of the compound was studied by transmission electron microscopy (TEM) and the composition of sterols on both treated and untreated cultures was determined. METHODS AND RESULTS: MCOD was tested at concentrations in the range 0.003-0.5% by the agar plate dilution method. The radial growth of the colonies treated with MCOD was measured against colonies from untreated cultures. The radial growth of colonies of both fungi and the spore germination of B. cinerea were partially or completely inhibited. Fragments of active growing colonies treated and untreated with MCOD were submitted to the conventional procedure for ultrastructural observation by TEM. Observations by TEM on colonies of B. cinerea and L. seditiosum under 0.1% MCOD revealed several autophagic-like vacuoles, morphological alterations on lomasome and lipid accumulations in the apical zone of hyphae of both fungi. Observations on spore germination of B. cinerea revealed the presence of strongly stained lipid accumulations retained by vacuoles at the cell periphery of young hyphae. The sterol composition of B. cinerea and L. seditiosum was determined on MCOD treated and untreated cultures by gas-chromatography/mass-spectrometry (GC-MS) with molecular ions and fragmentation patterns characteristics of ergosterol (M+396) and dihydroergosterol (M+398) in both fungi. CONCLUSIONS: The morphological alterations are consistent with an unspecific mode of action of MCOD causing inhibition of normal growth or damaging the fungi cells. TEM observations suggest a mechanism of resistance based on the retention of MCOD by the lipid accumulation. SIGNIFICANCE AND IMPACT OF THE STUDY: The results obtained in the present work afforded a better understanding of the mode of action of a resin acid derivative on phytopathogenic fungi. The inhibition growth of both fungi by MCOD demonstrates the antifungal activity of this compound and the interest on further in vivo studies, in order to evaluate its potential as a benign alternative to conventional fungicides.

A physiological and enzymatic study of Debaryomyces hansenii growth on xylose- and oxygen-limited chemostats.

The effect of changing growth rate and oxygen transfer rate (OTR) on Debaryomyces hansenii physiology was studied using xylose-limited and oxygen-limited chemostat cultures, respectively, and complemented with enzymatic assays. Under xylose-limited chemostat (oxygen-excess), neither ethanol nor xylitol was produced over the entire range of dilution rate ( D). The maximal volumetric biomass productivity was 2.5 g x l(-1) x h(-1) at D =0.25 h(-1) and cell yield was constant at all values of D. The respiratory rates and xylose consumption rate increased linearly with growth rate but, above 0.17 h(-1), oxygen consumption rate had a steeper increase compared to carbon dioxide production rate. Enzymatic analysis of xylose metabolism suggests that internal fluxes are redirected as a function of growth rate. For values of D up to 0.17 h(-1), the xylose reductase (XR) titre is lower than the xylitol dehydrogenase (XDH) titre, whereas above 0.17 h(-1) XR activity is about twice that of XDH and the NADPH-producing enzymes sharply increase their titres indicating an internal metabolic flux shift to meet higher NADPH metabolic requirements. Moreover, the enzymes around the pyruvate node also exhibited different patterns if D was above or below 0.17 h(-1). Under oxygen-limited chemostat (xylose-excess) the metabolism changed drastically and, due to oxidative phosphorylation limitation, cell yield decreased to 0.16 g g(-1) for an OTR of 1.4 mmol l(-1) h(-1) and xylitol became the major extracellular product along with minor amounts of glycerol. The enzymatic analysis revealed that isocitrate dehydrogenase is not regulated by oxygen, whereas XR, XDH and the NADPH-producing enzymes changed their levels according to oxygen availability.

Polysaccharide synthesis as a carbon dissipation mechanism in metabolically uncoupled Xanthomonas campestris cells.

The utilization of xanthan metabolism as an excess carbon dissipation path in Xanthomonas campestris cells under sub-lethal acid stress was studied. To highlight growth limitation during metabolic uncoupling due to acid toxicity a antibiotic was added. The simultaneous addition of enoxacin and acetic acid showed that the xanthan production per unit of biomass raises with increasing concentrations of enoxacin, which seems to indicate that when the cell is prevented from growing it finds a path to convey the extra carbon. In parallel, although the effect of acetic acid is not very significant, its presence appears to increase xanthan. This tendency seems to be accentuated with increasing concentrations of enoxacin. In fact, in presence of 0.15 mM of acetic acid, 2.88 and 5.76 microM of antibiotic produces xanthan/biomass yields of 8.13 and 9.82 g g(-1) which drop to below half those values (3.55 g g(-1)) when enoxacin is removed. When enoxacin was kept constant, xanthan/biomass yields showed small increments with the increase of acetic acid. Thus, with 1.44, 2.88 and 4.32 microM enoxacin concentrations, the addition of organic acid produces a 6--8% stimulation of xanthan.

Antimicrobial activity of diterpene resin acid derivatives.

C-13 deisopropylated and/or C-7 oxidized resin acid derivatives were tested against various microorganisms to determine structural features responsible for biological activity and to determine the influence of the C-13 isopropyl group on antimicrobial activity. Test results show that methyl cis and trans 7-oxo-13-deisopropyldehydroabietate and a mixture of both isomers exhibited activity against fungi and bacteria.

Co-metabolism and microbial growth in the biodegradation of alkylbenzenesulphonates.

Two organisms, CCMI507 and CCMI852, degrading undecylbenzenesulphonate (LAS) by the ortho- and meta-cleavage pathways were studied in cultures where glucose was used as carbon and energy source. CCMI507 (ortho-pathway) started the degradation of LAS at the beginning of the culture development in parallel with glucose utilization. The degradation followed a steady profile of degradation until 77% of LAS was degraded in the culture containing initially 5 mg l-1 of the compound and 81% in the cultures containing initially 10 and 20 mg l-1 of LAS, after 72 h fermentation. The organism CCMI852 (meta-pathway) started degrading the compound only after 20 h, when 75% of glucose was spent and well within the stationary-phase. After 72 h fermentation the level of degradation by CCMI852 varied from 70% (5 mg l-1 of LAS) to around 75% (10 and 20 mg l-1 of LAS).