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 one was able to convert R-(+)-limonene and 4 were able to bioconvert (−)-β-pinene to oxygenated monoterpenes. The metabolites recovered were α-terpineol (2856.54 ± 50.23 mg/L) and fenchol (traces) for Aspergillus niger ATCC 16404, α-terpineol (688.13 ± 41.27 mg/L) for A. niger ATCC 9642, α-terpineol (172.07 ± 32.94 mg/L) for A. niger ATCC 1004 and α-terpineol (24.38 ± 2.78 mg/L) and trans-pinocarveol (traces) for Penicillium camembertii ATCC 4845. After screening and optimization experiments, 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.     

Palygorskite sheets prepared via tape casting for wound healing applications

The main objective was to increase the applicability of palygorskite by palygorskite sheets using a tape casting method. The stability of the suspension was investigated and the tapes were characterized by TGA/DTA, XRD, and SEM-FEG. The antimicrobial activity was analyzed in order to test the applicability of a newly modified drug release system that incorporates neomycin in palygorskite. Preliminary results showed that the palygorskite sheet prepared via the tape casting is promising for wound healing applications.     

Evaluation of the conditions of carotenoids production in a synthetic medium by Sporidiobolus salmonicolor (CBS 2636) in a bioreactor

This work studied the cultivation conditions for the production of carotenoids by Sporidiobolus salmonicolor (CBS 2636) in a bioreactor. A Plackett–Burman design was used for the screening of the most important factors, followed by a complete second order design, to maximise the concentration of total carotenoids. The maximum concentration of 3425.9 μg L^?1 of total carotenoids was obtained in a medium containing 80 g L^?1 glucose, 15 g L^?1 peptone and 5 g L^?1 malt extract, with an aeration rate 1.5 vvm, 180 r.p.m., 25 °C and an initial pH of 4.0. Fermentation kinetics showed that the maximum concentration of total carotenoids was reached after 90 h of fermentation. Carotenoid bio‐production was partially associated with cell growth. The specific carotenoid production (Y_P/X) was 238 μg carotenoids/g cells, whereas Y_P/S (substrate to product yield) was 41.3 μg g^?1. The specific growth rate (μ_x) was 0.045 h^?1. The highest cell and total carotenoid productivity were 0.19 g L^?1 h^?1 and 56.9 μg L^?1 h^?1, respectively.     

Effect of pressure,depressurization rate and pressure cycling on the inactivation of Escherichia coli by supercritical carbon dioxide

This work is focused on the use of supercritical carbon dioxide to inactivate the pathogenic Escherichia coli. For this purpose, the experimental design methodology was employed to evaluate the effects of pressure (8–28 MPa), depressurization rate (1–11 MPa min^?1) and pressure cycling (1–5 cycles) on the microorganism inactivation using the static-synthetic method in a variable-volume reactor. The number of pressure cycles and system pressure showed a significant influence on E. coli inactivation with supercritical CO₂, indicating that the increase in the number of pressure cycles and system pressure improve inactivation efficiency. Microbial inactivation followed first order reaction kinetics, where the rates increased with increasing pressure from 8 to 16 MPa. The decimal reduction times (D) ranged from 1.03 to 5.35 min. The pressure dependence of the E. coli specific inactivation rates can be described by the z value, which was found to be 11.4. The results reported here may be useful to provide an effective non-thermal sterilization of foods in pilot/industrial scale.     

Application of Origanum majorana L. essential oil as an antimicrobial agent in sausage

This work reports on the antimicrobial activity in fresh sausage of marjoram (Origanum majorana L.) essential oil against several species of bacteria. The in vitro minimum inhibitory concentration (MIC) was determined for 10 selected aerobic heterotrophic bacterial species. The antimicrobial activity of distinct concentrations of the essential oil based on the highest MIC value was tested in a food system comprising fresh sausage. Batch food samples were also inoculated with a fixed concentration of Escherichia coli and the time course of the product was evaluated with respect to the action of the different concentrations of essential oil. Results showed that addition of marjoram essential oil to fresh sausage exerted a bacteriostatic effect at oil concentrations lower than the MIC, while a bactericidal effect was observed at higher oil concentrations which also caused alterations in the taste of the product.     

Study of the Extraction,Concentration, and Partial Characterization of Lipases Obtained from <Emphasis Type="Italic">Penicillium verrucosum</Emphasis> using Solid-State Fermentation of Soybean Bran

Microbial lipases constitute an important group of enzymes with high biotechnological potential, but their application is limited due to production costs. The present study aimed to evaluate the extraction conditions, concentration with ammonium sulfate, and the partial characterization of the enzyme extracts (in terms of the optimum temperature and pH and their stability at low temperatures). It was shown that the optimal extraction conditions were established at 37 °C and pH of 7.0 and that the best conditions for precipitation with ammonium sulfate were with 60% saturation for 5 h. In the partial characterization of the concentrated extract, the optima conditions were obtained at 42 °C and pH of 8.5. In a study carried out with the concentrated enzymatic extract, the hydrolytic activity was shown to be practically the same as the initial value after 91 days of storage at both 4 and −10 °C.