Diah Mardiana

Effect of Metal Ions on Pectinase Activity from Aspergillus niger on Purifying Guava Fruit

Pectinase can be used on various fruit juices clarification; however, the activities can be affected by their metal ions content. The purpose of this study was to determine the type of metal ions inhibition i.e. Zn 2+ ; Mg 2+ and Ca 2+ on the pectinase activity of Aspergillus niger , and its potential application in guava juice clarification. Activity assays performed at pH 5, temperature 50°C during 55minutes and each ion concentration were 2-10 mM. Galacturonic acid concentration, as the product of pectin substrate hydrolysis, used as the basis for determining its activity and analyzed by visible spectrophotometry. The results showed that the ions concentration of Zn 2+ and Mg 2+ more than 4 mM were inhibitor for pectinase activity while Ca 2+ ion concentration was 6mM. K I values for the metal ions Zn 2+ ; Mg 2+ and Ca 2+ at concentrations of 6mM were 176.99; 326.09 and 280.37 mM respectively. Pectinase from Aspergillus niger were able to reduce 18% of pectin of guava juice.

Early Poly Mass Effect (trimethylene-sebasat) On Biodegradation Rate In Liquid Media Using Mucor Miehei In Aerobic

The author has conducted research about the effect of poly(trimethylene-sebacate) mass toward the rate of biodegradation using Mucor miehei in aerobic liquid media. Poly(trimethylene-sebacate) is a biodegradable linear aliphatic polyester, that can be degraded by Mucor miehei lipase. To determine the effect of poly(trimethylene-sebacate) mass in the biodegradation, the mass of poly(trimethylene-sebacate) were varied 0.06 g, 0.08 g, 0.1 g, 0.12 g and 0.14 g. Biodegradation process carried out for 12 hours, using liquid of Complex media, which was nutrient rich for Mucor miehei growth, and solution at pH 5. The resulting CO2 gas was flowed into the 50 mL reservoir of 0.1 M NaOH, followed by titration using 0.05 M HCl and MO (methyl orange) and PP (phenolptalein) indicator. The rate of CO2 gas were 0.287 x 10-3 M/h; 0.102 x 10-3 M/h; 0.137 x 10-3 M/h; 0.016 x 10-3 M/h; and 0.039 x 10-3 M/h respectively. The greater rate of CO2 produced the lower mass of poly(trimethylene-sebacate).

CHARACTERIZATION OF IMMOBILIZED LIPASE IN ALUMINOSILICATE FOR LACTOSYL PALMITATE SYNTHESIS

Whey lactose can be esterified enzymatically by using immobilized lipase. The lipase can be isolated from Rhizopus oryzae, purified and immobilized in mesoporous aluminosilica. The use of immobilized lipase has advantages, there are longer shelf life and repeatable use. It is necessary to characterize the immobilized lipase dan ester product. The aim of the research was to characterize immobilized lipase, including determination lipase adsorption type in mesoporous aluminosilicate, immobilized lipase stability during storage time, efficiency of repetitive use of immobilized lipase. The result showed that lipase adsorption in mesoporous aluminosilicate was physical adsorption type through hydrogen bound and electrostatic interaction. Immobilized lipase stability was relatively constant at storage temperature 5 °C for 25 days resulting in 98.16% of initial activity. The repetitive use of immobilized lipase showed efficient until 5 uses within activity of 50.22%. The IR spectra of lactosyl palmitate from both whey and pure lactose result showed bands at wavelength number of 3462 cm -1 (OH bond), 1739 cm -1 and 1747 (C=O ester bond) 1295 cm -1 dan 1242 cm -1 (C-O ester bond). In addition, the HLB value for lactosyl palmitate (whey) 4.708 and lactosyl palmitate (pure lactose) 4.715, therefore both lactosyl palmitate is appropriate as emulgator in W/O.