Optimization of esterification activity of lipase from Candida rugosa immobilized using microwave irradiation

Lipases are very efficient biocatalysts with wide application in synthesis of important ingredients of food, cosmetics and pharmaceutical products, due to their capacity to catalyze both, ester synthesis and ester hydrolysis. The preparation of stable and active immobilized derivatives of lipases is necessity for their application in industrial enzymatic processes. In this work, the optimization of lipase from C. rugosa immobilization by microwave irradiation was performed, since it was previously reported that immobilization process can be drastically accelerated by means of microwave irradiation, even resulting with slight increase of lipase activity. Eupergit®, commercial support with active epoxy groups, was used as immobilization support. In first stage of our study, the immobilization time and ionic strength of immobilization buffer were optimized. It was found out that the highest immobilized activity can be achieved at high ionic strengths (1 M buffer) after 3 min, while further increase of immobilization time led to decrease of lipase activity. Then, the immobilized derivative obtained at optimum conditions was applied in synthesis of amyl isobutyrate in organic solvent. Key reaction factors (temperature, water concentration, immobilized lipase concentration, and substrate molar ratio) were optimized using response surface methodology. The substrate conversion higher above 85% was achieved in our study. The statistical analysis revealed that each of analyzed factors had significant effect on yield of ester, with initial enzyme concentration and substrate molar ratio being the most prominent factors. The second-order regression model that describes the effect of all four factors on substrate conversion was established. The optimum values of factors were: temperature 50°C, initial immobilized enzyme concentration 220 mg ml-1, added water concentration 0.1% (v/v), and molar ratio acid/alcohol 2.5.Lipaze su enzimi koji imaju široku primenu u prehrambenoj, kozmetičkoj i farmaceutskoj industriji. U industrijskoj praksi primenjuju se imobilisane lipaze jer se imobilizacijom povećava njihova stabilnost i ekonomičnost enzimskih postupaka. U ovom radu optimizovana je imobilizacija lipaze iz C. rugosa na komercijalni nosač Eupergit® pomoću mikrotalasnog zračenja. Vreme izlaganja mikrotalasima i molaritet korišćenog pufera optimizovani su sa ciljem dobijanja imobilizata maksimalne aktivnosti. Radi optimizovanja reakcije sinteze amil-izobutirata, pomoću centralnog kompozitnog rotatabilnog plana ispitan je uticaj četiri reakciona faktora. Ustanovljeno je da su optimalni uslovi sinteze estra temperatura 50°C, početna koncentracija imobilisanog enzima 220 mg ml-1, koncentracija dodate vode 0,1% i molarni odnos supstrata 2,5

Feeding value of low quality grass silage supplemented with maize silage for sheep

The objective of this experiment was to study the effects of interactions between low quality grass silage (GS) dominated by orchardgrass and maize silage (MS) on ad libitum intake, digestibility and nitrogen retention in wether sheep. The study consisted of four feeding treatments involving GS and MS alone and GS and MS mixtures in a ratio of 67:33 or 33:67 (dry matter (DM) basis) fed twice daily. The GS was high in DM (463 g kg 1), neutral detergent fibre (715 g kg 1DM) and acid detergent fibre (429 g kg 1DM) while low in crude protein (90.1 g kg 1DM). The DM content (g kg 1) and starch concentration (g kg 1DM) of MS were 264 and 211, respectively. The inclusion of MS into diet had positive linear effects on fresh matter ad libitum intake (kg d 1 and g kg 1M0.75d 1) (P < 0.01 and P < 0.001 respectively), digestibility of DM (P < 0.01), organic matter (P < 0.01), acid detergent fibre (P < 0.05), starch (P < 0.001), digestibility of organic matter in DM (D-value) (P < 0.001), nitrogen intake (P < 0.01) and nitrogen output in faeces (P < 0.01). A positive associative effect of low quality GS and MS was observed for ad libitum intake (kg d 1 and g kg 1M0.75d 1) of fresh matter (quadratic, P < 0.01), DM (quadratic, P < 0.001 and P < 0.01 respectively) and organic matter (P < 0.001), for digestibility of DM, neutral detergent fibre, acid detergent fibre, crude protein, starch and D-value (quadratic, P < 0.01), digestibility of organic matter (quadratic, P < 0.05), nitrogen intake (quadratic, P < 0.001) and nitrogen balance (quadratic, P < 0.05). It was concluded that differences between low quality GS and MS resulted in positive associative responses of GS and MS for all parameters measured (intake, digestibility and nitrogen retention).vo

The content and composition of humus in pseudogleys of slopes and plains in South Macva and Pocerina

The scope of this paper was to examine the influence of two subtypes of pseudogley soil (of planes and of slopes) and three different land uses (forest, grassland and arable land) on the content and composition of humus in south Mačva and Pocerina. The humus content was determined by dichromate method, and humus components were measured using the method proposed by Kononova and Belcikova. The studied soils are mostly characterized by low humus content. Humus content is significantly higher in pseudogleys of plains compared to pseudogleys of slopes. Pseudogleys under grass and crops have significantly lower content of humus compared to the pseudogleys under forest. Important characteristic of humus composition of surface horizon is dominant portion of fulvic over humic acids. Pseudogleys of plains have statistically significant higher amount of humic acids. The composition of humus is significantly different in pseudogley under forest compared to pseudogleys under grass and crops: it has more fulvic acids, less humin, and lower Ch:Cf ratio. Changes in pseudogley land use have produced better humus quality.Cilj ovog rada je ispitivanje uticaja dva podtipa pseudogleja (ravničarskog i obronačnog) i tri načina korišćenja (šuma, travnjak, njiva) na sadržaj i grupno-frakcioni sastav humusa na području južne Mačve i Pocerine. Ispitivana zemljišta generalno karakteriše uglavnom nizak sadržaj humusa. Statistički značajno je sadržaj humusa veći u ravničarskom podtipu pseudogleja u poređenju sa obronačnim. U pseudogleju pod travnom vegetacijom i na obradivim površinama došlo je do statistički značajnog smanjenja sadržaja humusa u poređenju sa pseudoglejom pod šumom. Bitna karakteristika grupno-frakcionog sastava humusa površinskog horizonta je dominacija fulvo nad huminskim kiselinama. Ravničarski pseudoglej sadrži statistički značajno više huminskih kiselina. Sastav humusa se značajno razlikuje u pseudogleju pod šumom u poređenju sa pseudoglejom pod travom i njivom: sadrži više fulvo kiselina, a manje humina i ima uži Ch:Cf odnos. Promena načina korišćenja pseudogleja dovela je do poboljšanja osobina humusa, odnosno donekle dovela do stabilizacije humusa i umanjila njegove inače veoma loše osobine

Importancia del cepillado antes de acostarse en la prevención de la caries. Estudio en una población infantil

En el presente trabajo nos planteamos si sería imprescindible el cepillado tres veces al día y, en caso contrario, en qué momento del día sería más importante la eliminación mecánica de la placa. Para ello, se planteó un estudio transversal correspondiente a 214 escolares de 6-12 años en el periodo comprendido en el curso 2004-5. A cada niño se le practicó el "Examen parcial o tipo ll/" recomendado por la Federación Dental Internacional, como procedimiento estándar para un estudio de prevalencia de caries. Hemos obtenido los siguientes resultados: 1. El cepillado de dientes antes de acostarse es un factor protector de la presencia de caries, siendo el correspondiente odd-ratio ajustado de 0.339 (intervalo de confianza al 95% [0.159; 0.722]). 2. El consumir azúcar más de una vez una vez al día tiene más riesgo de aparición de caries que si consumen una vez al día, siendo el correspondiente odd-ratio ajustado de 1.998 (intervalo de confianza al 95% [1.090; 3.665]). 3. Los niños que acuden a un colegio público tienen más riesgo de presentar caries que los que asisten a un colegio privado. Siendo el correspondiente odd-ratio ajustado de 2.019 (intervalo de confianza al 95% [1.105; 3.691]). 4. Se cumplen en la población estudiada los objetivos marcados sobre caries dental por la OMS para el año 2000