Meaty aroma notes from free amino acids and thiamine in nitrite-reduced, dry-fermented, yeast-inoculated sausages.

The contribution of free amino acids and thiamine to the production of potent meat aroma compounds in nitrite-reduced, dry-fermented sausages inoculated with a D. hansenii strain was the objective of this study. For this, three different sausage formulations were manufactured; a control and two formulations reduced by half in nitrate and nitrite and one of them inoculated with D. hansenii. Free amino acids, thiamine content and savoury volatile compounds were analysed. Eleven savoury volatile compounds were quantitated. Among them, the most potent compounds above their odour thresholds were 2-methyl-3-furanthiol, 2-acetyl-1-pyrroline, methional, dimethyl trisulfide and methyl-2-methyl-3-furyl disulfide. Their generation was affected by D. hansenii inoculation as shown by the decrease in methional and methyl 2-methyl-3-furyl disulfide content, and the increase of methionol. Nitrate and nitrite reduction did not significantly affect amino acid and thiamine contents.

Screening of Debaryomyces hansenii Strains for Flavor Production under a Reduced Concentration of Nitrifying Preservatives Used in Meat Products.

A total of 15 Debaryomyces hansenii strains from different food origins were genetically characterized and tested on a culture medium resembling the composition of fermented sausages but different concentrations of nitrifying preservatives. Genetic typing of the D. hansenii strains revealed two levels of discrimination: isolation source or strain specific. Different abilities to proliferate on culture media containing different concentrations of nitrate and nitrite, as sole nitrogen sources and in the presence of amino acids, were observed within D. hansenii strains. Overall metabolism of amino acids and generation of aroma compounds were related to the strain origin of isolation. The best producers of branched aldehydes and ethyl ester compounds were strains isolated from pork sausages. Strains from cheese and llama sausages were good producers of ester compounds and branched alcohols, while vegetable strains produced mainly acid compounds. Nitrate and nitrite reduction affected in different ways the production of volatiles by D. hansenii.

Enhanced production of bacterial cellulose by using Gluconacetobacter hansenii NCIM 2529 strain under shaking conditions.

Bacterial cellulose (BC), a biopolymer, due to its unique properties is valuable for production of vital products in food, textile, medicine, and agriculture. In the present study, the optimal fermentation conditions for enhanced BC production by Gluconacetobacter hansenii NCIM 2529 were investigated under shaking conditions. The investigation on media components and culture parameters revealed that 2 % (w/v) sucrose as carbon source, 0.5 % (w/v) potassium nitrate as nitrogen source, 0.4 % (w/v) disodium phosphate as phosphate source, 0.04 % (w/v) magnesium sulfate, and 0.8 % (w/v) calcium chloride as trace elements, pH5.0, temperature 25 °C, and agitation speed 170 rpm with 6 days of fermentation period are optimal for maximum BC production. Production of BC using optimized media components and culture parameters was 1.66 times higher (5.0 g/l) than initial non optimized media (3.0 g/l). Fourier transform infrared spectroscopy spectrum and comparison with the available literature suggests that the produced component by G. hansenii in the present study is pure bacterial cellulose. The specific action of cellulase out of the investigated hydrolytic enzymes (cellulase, amylase, and protease) further confirmed purity of the produced BC. These findings give insight into conditions necessary for enhanced production of bacterial cellulose, which can be used for a variety of applications.

[The genetic susceptibility to leprosy in humans]. / Susceptibilité génétique à la lèpre chez l'homme.

The capacity of certain individuals to resist certain diseases, including leprosy, has for a long time been considered as being influenced by genetic factors. The clinical and pathological spectrum of leprosy, epidemiological heterogeneity, both geographic and ethnic, in the prevalence of polar forms, may be explained by genetic differences in host resistance. While the specific genes in question have not been identified, recent studies suggest a genetic basis for differences in the capacity of macrophages in the host to reduce bacterial multiplication. Experimental models analyzing the reactions of antimycobacterial defence have underscored at existing differences in resistance or vulnerability to infection (M. bovis, BCG, M. lepraemurium, M. tuberculosis) were guided by a dominant gene which exists in two allelic forms, bcgr and bcg5. The bcgr allele confers resistance and is more dominant than the bcgs allele which represents greater vulnerability to infection. The murine candidate gene for the bcg gene has been named NRAMP (Natural Resistance-associated Macrophage Protein). Even though the exact function of NRAMP is not currently known, it has been demonstrated that this gene is expressed mainly in macrophages, and that it brings about increased bacteriostatic capacity in these cells. NRAMP is structurally homologous to the family of membranous proteins having a transport function linking ATP. NRAMP is similar to the membranous bacterial system transporting nitrites. The NRAMP protein is also involved as a signal of transduction during the activation of macrophages. It is therefore possible to conceive of genetic polymorphism at this locus intervening in specific and non-specific immune responses to infection. Apart from such potential polymorphism during the initial phase of infection, immunogenetic studies suggest that the polymorphism of class II HLA molecules could intervene in the evolution of secondary immune response to M. leprae. Knowing that HLA molecules are expressed in a co-dominant form, and attributing extraordinary allelic polymorphism to this locus, there may be a rather wide range of immune responses to the M. leprae antigens in subjects with discordant HLA and in populations which have varied genetic profiles. In general it has been acknowledged that HLA-DR isotypes are associated with protective response, while HLA-DQ isotypes are said to be associated with multibacillary lepromatous forms. The chief role of the HLA systems controlling cell-mediated immunity leads to the probability that differences in HLA haplotypes could contribute to the wide spectrum of immune responses observed in leprosy. Genetic determinants of resistance to leprosy cannot be described in a straightforward manner using a classic approach because the complex mechanisms of resistance, yet to be clarified and for which at least two loci are believed to be contributory, may be re-assessed like a multifactorial, multigenetic complex in which environmental events linked to the transmission of M. leprae, its duration, intensity and host factors, varying as a function of time, intervene. A close study of each element and better understanding of the physiological and pathological mechanisms of infection and disease are necessary in order to state the influence of genetic factors on each of them with greater precision.