Evaluation of the induction of lipolytic enzymes froma Pseudomona aeruginosa isolated from african palm fruit (Eleasis guimeensis) / Evaluación de la inducción de enzimas lipolíticas a partir de una Pseudomona aeruginosa aislada del fruto de palma africana (Eleasis guineensis)

Background: Extracellular lipases are found in the culture broth when the fermentation is at the end of the exponential phase. Lipases can be induced easily since they are produced by the presence of oily sources or other materials as surfactants, fatty acids, some esters, glycerol and biliary salts. Objective: The aim of this work is to study the effect of carbon source concentration and the use of inductors on biomass production, and the lipolytic activity of a bacterium isolated from mature palm oil fruits. Methods: The yield biomass/substrate was evaluated with glucose as carbon source at different concentrations (3, 5, 7, 10, 15 y 20 g/L) by dry weight and OD (600 nm). Lipolytic activity was evaluated by spectrophotometric assay using p-nitrofenilpalmitate at 37°C for 15 min. Results: Gram negative microorganisms with lipolytic activity isolated from palm fruit were identified as Pseudomona aeruginosa. The growth of the bacteria was inhibited when glucose was used at concentrations greater than 5%. The production of lipase was induced by using three inducers (Palm oil, Tween 20 and palm oil:Tween 20 mixture), at three different induction times (0, 11 and 18 hours of fermentation). The highest activity (3,81 µmoles/mL*min) was observed when the palm oil:Tween 20 mixture was added at 11 hours of fermentation. The kinetic of p-nitrophenylpalmitate hydrolysis using the supernatant of a culture induced with palm oil:Tween 20 mixture at 11 hours showed the production of p-nitrophenol beyond 300 minutes, with the greatest hydrolysis rate during the first 7 minutes. Conclusions: The growth of P. aeruginosa was not affected by using glucose as carbon source at concentrations of 3% and 5%. There was a basal level of lipase production without inducer, and greater lipolytic activity was achieved with the addition of inducers.

Caracterización de películas de almidón modificado de arracacha y su eventual aplicación como empaque de alimentos / Modified arracacha starch films characterization and its potential utilization as food packaging

Background: The use of petroleum-based plastics has increased in recent years. These materials are resistant and economically competitive. However, the environmental pollution caused by these is very high. For this reason, some research has focused on the alleviation of this environmental problem, mainly through the development and use of biodegradable polymers. The food industry as an economic dynamic sector is looking for new environmental and secure alternatives for the consumer welfare. In packaging sector, materials should be renewable and final products must be recyclable, innovative and economically competitive. New starch sources could be an adequate alternative. Objetive: The main objective in this research project was to evaluate the chemical modification of arracacha starch, testing different plasticizer concentrations, as a raw material for food biodegradable packaging production. Methods: The arracacha native starch was acetylated or oxidized to produce biodegradable films. The starches were characterized by infrared spectroscopy, scanning electron microscopy, x-ray diffraction and volumetric techniques. Results: Films made with acetylated starch presented more transparency. Native starch films had lower water solubility and greater stability in acid and alkaline conditions. The effect of alkaline conditions was higher than the acid conditions for the three types of films in all treatments. Conclusion: Physicochemical properties of the films were directly influenced by the amount of plasticizer used and by the starch modification type. The physicochemical and microbiological tests of the meat show the possible use of starch films for packaging.