Analytical methods in fatty acid analysis for microbial applications: the recent trends.

Fatty acids are among the most important components of many biological systems and have been highlighted in many research fields in recent decades. In the food industry, it is important to check the amount and types of fatty acids in edible oils, beverages and other foods products, and checking the fatty acids parameters are among the quality control parameters for those products. In medical applications, investigation of fatty acids in biological samples and comparing imbalances in them can help to diagnose some diseases. On the other hand, the development of cell factories for the production of biofuels and other valuable chemicals requires the accurate analysis of fatty acids, which serve as precursors in development of those products. As a result, given all these different applications of fatty acids, rapid and accurate methods for characterization and quantification of fatty acids are essential. In recent years, various methods for the analysis of fatty acids have been proposed, which according to the specific purpose of the analysis, some of them can be used with consideration of speed, accuracy and cost. In this article, the available methods for the analysis of fatty acids are reviewed with a special emphasis on the analysis of microbial samples to pave the way for more widespread metabolic engineering research.

Preparation and characterization of poly-lactic acid based films containing propolis ethanolic extract to be used in dry meat sausage packaging.

In this study, active poly lactic acid (PLA) films containing 0, 10, 20 and 40% w/w propolis extract (PE), as active agent, were developed. A high amount of phenolic content (PC) was measured in PE. The antioxidant effect of active PLA films was determined by measuring the PC of sausage slices after 0, 2 and 4 days storage at refrigerator. Results showed that phenolic compounds of PE were released from PLA films in quantities proportional to PE concentration. Disc diffusion test indicated that PE showed an inhibitory effect against Staphylococcus aureus and Pseudomonas aeruginosa bacterial species but was more effective against gram-positive species. PE containing PLA films had antimicrobial effect on S. aureus while in the case of P. aeruginosa, PLA/PE films needed polyethylene glycol (PEG)/CaCO3 content to show inhibitory effect. Addition of PE changed the tensile strength, elongation at break and elastic modulus of PLA films negatively. However, addition of PEG/CaCO3 improved the film mechanical properties and antimicrobial effect of films.

Spectrophotometric determination of sulfide based on peroxidase inhibition by detection of purpurogallin formation.

This paper presents a new method for spectrophotometirc detection of sulfide applying fungal peroxidase immobilized on sodium alginate. The sensing scheme was based on decrease of the absorbance of the orange compound, purpurogallin produced from pyrogallol and H2O2 as substrates, due to the inhibition of peroxidase by sulfide. Absorbance of purpurogallin was detected at 420nm by using a spectrophotometer. The proposed method could successfully detect the sulfide in the concentration range of 0.6-7.0µM with a detection limit of 0.4µM. The kinetic parameters of Michaelis-Menten with and without sulfide were also calculated. Possible inhibition mechanism of peroxidase by sulfide was deduced according to the variation of parameters and uncompetitive mechanism was observed with respect to hydrogen peroxide. The current method provides an easy to use method for sulfide detection in water samples.

Amperometric sulfide detection using Coprinus cinereus peroxidase immobilized on screen printed electrode in an enzyme inhibition based biosensor.

In the present work, an amperometric inhibition biosensor for the determination of sulfide has been fabricated by immobilizing Coprinus cinereus peroxidase (CIP) on the surface of screen printed electrode (SPE). Chitosan/acrylamide was applied for immobilization of peroxidase on the working electrode. The amperometric measurement was performed at an applied potential of -150 mV versus Ag/AgCl with a scan rate of 100 mV in the presence of hydroquinone as electron mediator and 0.1M phosphate buffer solution of pH 6.5. The variables influencing the performance of sensor including the amount of substrate, mediator concentration and electrolyte pH were optimized. The determination of sulfide can be achieved in a linear range of 1.09-16.3 µM with a detection limit of 0.3 µM. Developed sensor showed quicker response to sulfide compared to the previous developed sulfide biosensors. Common anions and cations in environmental water did not interfere with sulfide detection by the developed biosensor. Cyanide interference on the enzyme inhibition caused 43.25% error in the calibration assay which is less than the amounts reported by previous studies. Because of high sensitivity and the low-cost of SPE, this inhibition biosensor can be successfully used for analysis of environmental water samples.