Comparative lethality kinetic curves and predictive models of f-value for listeria monocytogenes using different sanitizers

The objective of this work was to evaluate the kinetic of inactivation of Listeria monocytogenes using peracetic acid, chlorhexidine, and organic acids as active agent, determining the respective D-, Z-, and F-values. From our knowledge, these important results from an industrial view point are not available in the current literature, mainly for organic acids, pointing out the main contribution of the present work. Lower D-values were obtained for peracetic acid and chlorhexidine, compared with the organic acids. For the reduction of 6 log10 of L. monocytogenes using peracetic acid, at 0.2, 0.1, and 0.05% are necessary 7.08, 31.08, and 130.44 min of contact, respectively. The mathematical models of F-values showed that at concentrations lower than 0.15% one can verify an expo-nential increase in F-values, for both de chlorhexidine and peracetic acid. The organic acids presented a linear behavior, showing slight variation in F-values, is even more effective in under dosage. The results obtained are of fundamental importance in terms of industrial strategy for sanitization procedure, permitting to choose the best relation product concentration/exposure time, aiming at reducing costs without compromising the disinfectant efficiency

Xanthan gum production and rheological behavior using different strains of Xanthomonas sp

The proposal of the present study was to select and carry out the molecular characterization of strains of Xanthomonas sp. in order to correlate with gum production and determine possible genetic alterations during the study. The gums produced were also evaluated rheologically. Ten strains of Xanthomonas were used in the screening and the best ones in terms of productivity were Xanthomonas campestris pv. mangiferaeindicae 1230 (8.93 g/L), X. campestris pv. campestris 254 (9.49 g/L) and X. campestris pv. campestris 1078 (9.67 g/L). The gum produced by X. campestris pv. mangiferaeindicae presented the best apparent viscosity. The results for the profiles of the bands produced by RAPD showed considerable genetic variability amongst the evaluated strains, making not possible to neither group the strains according to pathovar or species, nor correlate the band profile with the productivity obtained. According to the RAPD analysis, no detectable mutations occurred in these bacteria during the study. © 2008 Elsevier Ltd. All rights reserved

Screening of microorganisms for bioconversion of (-)β-pinene and R-(+)-limonene to α-terpineol

This work is focused on the bioconversion of (-)β-pinene and R-(+)-limonene to α-terpineol. To carry out the present study, 400 microorganisms were tested for their ability to bioconvert the substrates. From the microorganisms, no onewas able to convert R-(+)-limonene and 4 were able to bioconvert (-)-β-pinene to oxygenated monoterpenes. The metabolites recovered were a-terpineol (2856.54 + 50.23 mg/L) and fenchol (traces) for Aspergillus niger ATCC 16404, a-terpineol (688.13 + 41.27 mg/L) for A. niger ATCC 9642, a-terpineol (172.07 +32.94 mg/L) for A. niger ATCC 1004 and a-terpineol (24.38 + 2.78 mg/L) and trans-pinocarveol (traces) for Penicillium camembertii ATCC 4845. After screening and optimizationexperiments, the best experimental condition for bioconversion of (-)β-pinene to α-terpineol was established using A. niger ATCC 16404 at 35 °C without addition of vitamin solution, yielding a conversion in α-terpineol of 15494.34 ± 193.87 mg/L. © 2010 Elsevier Ltd