The potential effect of FOS and inulin upon probiotic bacterium performance in curdled milk matrices

Inulin and fructooligosaccharides were studied for their prebiotic effect upon growth/survival of probiotic bacteria and technological potential in probiotic food processing, via characterization of glycolysis, proteolysis and lipolysis in curdled milk matrices; the ultimate goal is the manufacture of synbiotic cheeses. Prebiotic compounds did not significantly affect growth/viability of all strains studied, except Lactobacillus acidophilus La-5. Proteolysis indices revealed considerable casein degradation in probiotic and synbiotic matrices inoculated with Bifidobacterium lactis B94 and Lactobacillus casei-01; lower values were achieved in those inoculated with L. acidophilus La-5, yet a synbiotic effect was apparent in NPN values. Lipolysis was not extensive over storage, irrespective of matrix type; however, interesting differences in terms of the qualitative free fatty acids profile were observed. CLA isomers, and α-linolenic and γ−linolenic acids were detected upon 15 d of ripening of all inoculated matrices. Principal component analysis was able to discriminate the various matrices according to degree of maturation, throughout the ripening period. Microbiological and biochemical parameters unfolded a very good technological potential, especially of B. lactis B94 and L. casei-01, to produce novel types of functional dairy matrices - although extrapolation to actual cheeses should still be done with care, because e.g. syneresis was not considered.     

Optical fibre-based methodology for screening the effect of probiotic bacteria on conjugated linoleic acid (CLA) in curdled milk

A methodology based on optical fibre (OF) detection was developed for screening the potential of CLA production by Lactobacillus casei-01, Lactobacillus acidophilus La-5 and Bifidobacterium lactis B94 in probiotic curdled milk. The OF based methodology was validated by comparison with an analytical method based on gas chromatography–mass spectrometry (GC–MS) and it showed comparable linearity (between 5 and 130 μg), accuracy and detection limits, which ranged from 1.92 to 2.56 μg for CLA methyl ester and oleic acid methyl ester, respectively. Furthermore, the proposed OF based methodology was an advantageous analytical methodology for screening CLA production in probiotic curled milk, due to its compact design and effective cost of analysis.     

Kinetics of L-tryptophan production from indole and L-serine catalyzed by whole cells with tryptophanase activity

The essential amino acid L-tryptophan can be produced by a condensation reaction between indole and L-serine, catalyzed by whole cells of Escherichia coli B1t-7A with tryptophanase activity. The reaction was previously studied using soluble tryptophanase, a kinetic mechanism proposed and the catalytic properties of the enzyme described. It is important, however, to determine the kinetic parameters of the reaction catalyzed by whole cells, if the process is to be designed with the catalyst in this form. The reaction stoichiometry was established, a mole of product being formed from a mole of each reactant, with no indication of side reactions under the conditions used. The two-substrate reaction kinetics were characterized and modelled, assuming an enzyme-substituted mechanism and no product inhibition. Theoretical consumption rates of indole were compared with experimental values obtained in a batch reactor system. The K(m) values of whole cells towards L-serine and indole were 1.79 M and 0.07 M, respectively. These values are, as expected, considerably higher than their counterparts for soluble tryptophanase.     

X-ray absorption near-edge structure analysis of arsenic species for application to biological environmental samples

Arsenic is an element that is ubiquitous in the environment and is known to form compounds with toxic, even carcinogenic properties. Arsenic toxicity is a function of its chemical form (species). Identification of arsenic species is necessary to accurately determine the transformation and fate of arsenicals as well as the actual risk posed by arsenic contamination. We report X-ray absorption near-edge structure (XANES) measurements of 16 biologically important arsenic compounds. Solid and aqueous standards were studied for differences in XANES spectral features, white line positions, stability during exposure to the beam, and stability between two beam exposures separated by 48 h. Samples containing As(III) (11870.0-11871.7+/-0.5 eV) and As(V) (11872.6-11875.3+/-0.5 eV) were easily distinguished by white line energies and could be further subdivided into a total of seven groups. Valuable examples include As(III)-sulfur compounds (11870.0+/-0.5 eV), arsenobetaine and arsenocholine (11872.6+/-0.5 eV), and a dimethyl arsinyl riboside (11873.3+/-0.5 eV). A growing number of environmental and biological studies use X-ray absorption spectroscopy (XAS) results to complement their more traditional analyses. Results provided here are intended to help make XAS more accessible to new users interested in the study of arsenic in the environment.     

Re-assembled casein micelles and casein nanoparticles as nano-vehicles for ω-3 polyunsaturated fatty acids

Food enrichment with nutraceuticals is an important goal, but its effectiveness in preventing diseases depends on preserving the functionality and bioavailability of the bioactive nutraceuticals. Omega-3 polyunsaturated fatty acids, such as docosahexaenoic acid (DHA), are important nutraceutical lipids, providing protection against cardiovascular and other diseases. Caseins are the major milk proteins whose biological function is to transport calcium, protein and phosphate from mother to the neonate. Our goal was to harness the natural self-assembly properties of caseins for protecting and delivering this important, but sensitive nutraceutical, DHA. Using spectrofluorescence we have shown, apparently for the first time, that casein can bind DHA with a relatively high affinity (K_b = (8.38 ± 3.12) × 10⁶ M⁻¹), and the binding ratio was 3–4 DHA molecules per protein molecule on average. Moreover, DLS particle characterization experiments have shown the formation of nanoparticles upon addition of DHA (predissolved in ethanol) to a casein solution. When calcium and phosphate were added (at 4 °C), DHA-loaded re-formed casein micelles (r-CM) with a size of 50–60 nm were obtained and there was no significant effect of the thermal treatment (74 °C, 20 s) on particle size. When casein nanoparticles (CNP) were prepared (at room temperature and without adding calcium and phosphate), DHA-loaded CNP with a diameter of 288.9 ± 9.6 nm were formed. Both the DHA-loaded r-CM and the DHA-loaded CNP systems showed a remarkable protective effect against DHA oxidation, demonstrating good colloidal stability and bioactive conservation throughout shelf life at 4 °C. These nanotechnologies may enable the enrichment of foods and beverages for promoting health of wide populations.     

Life cycle assessment of Jatropha biodiesel as transportation fuel in rural India

Since 2003 India has been actively promoting the cultivation of Jatropha on unproductive and degraded lands (wastelands) for the production of biodiesel suitable as transportation fuel. In this paper the life cycle energy balance, global warming potential, acidification potential, eutrophication potential and land use impact on ecosystem quality is evaluated for a small scale, low-input Jatropha biodiesel system established on wasteland in rural India. In addition to the life cycle assessment of the case at hand, the environmental performance of the same system expanded with a biogas installation digesting seed cake was quantified. The environmental impacts were compared to the life cycle impacts of a fossil fuel reference system delivering the same amount of products and functions as the Jatropha biodiesel system under research. The results show that the production and use of Jatropha biodiesel triggers an 82% decrease in non-renewable energy requirement (Net Energy Ratio, NER = 1.85) and a 55% reduction in global warming potential (GWP) compared to the reference fossil-fuel based system. However, there is an increase in acidification (49%) and eutrophication (430%) from the Jatropha system relative to the reference case. Although adding biogas production to the system boosts the energy efficiency of the system (NER = 3.40), the GWP reduction would not increase (51%) due to additional CH₄ emissions. For the land use impact, Jatropha improved the structural ecosystem quality when planted on wasteland, but reduced the functional ecosystem quality. Fertilizer application (mainly N) is an important contributor to most negative impact categories. Optimizing fertilization, agronomic practices and genetics are the major system improvement options.