Penghasilan ekso-poligalakturonase oleh aspergillus niger daripada ekstrak pektin daun nephrolepis biserrata dalam fermentasi keadaan pepejal

Abstract

Pectinase is an important enzyme especially in food and medicinal industries. Production of pectinase from fermentation of microorganisms requires pectin as an inducer, which is usually derived from citrus extracts. However, the ability of lignocellulosic material to produce pectin has not been much explored. Therefore, this study was conducted to produce exo-polygalacturonase enzymes (one of the pectinase enzymes) from Aspergillus niger using pectin extracted from the Nephrolepis biserrata leaves (a type of fern) which are available in abundance in the tropical and subtropical countries. In this study, the optimum production for the extraction of pectin from Nephrolepis biserrata leaves was 8.16% (g/g) with pH of 1.5, extraction time at 76.32 min and temperature at 100 °C. The pectin was further characterized and compared with a commercial pectin when it was used in solid state fermentation to produce exo-polygalacturonase from Aspergillus niger. In addition, the Nephrolepis biserrata leaves were also treated and used as substrates in addition to the ferm entation media used. The central composite design was used to optimize four significant variables resulted from the screening process that has been analyzed for production of exo-polygalacturonase. The variables included incubation time, temperature, concentration of pectin and moisture content. The optimum exopolygalacturonase production was obtained at 54.64 U/g with the conditions of the significant variables as 120 h of incubation time, 34 °C, 5.0 g/L of pectin concentration and 75.26% of moisture content. For partial characterization of exopolygalacturonase, the optimum temperature and pH were found to be 50 °C and pH of 4.0, respectively. Temperature stability of exo-polygalacturonase activity by Aspergillus niger was achieved at 40 °C to 50 °C up to 60 min of the incubation time. Exo-polygalacturonase was stable at pH of 3 to pH of 7 after 120 min of incubation, with the relative activity above 70%. Later, the kinetic constants and coefficients were determined from the Monod Model and Leudeking Piret equation with (j,max = 0.043 per hour, Ks = 0.473 g/L, Yx/s = 0.149 mg/g, Y E/s = 16.43 U/L and Y e /x = 114.4 U/mg. The value of specific enzyme levels were determined at, qE = 4.79 U/(mg.h) and the specific glucose consumption rate is qs = 0.289 g/(mg.h). Therefore, it can be concluded that Nephrolepis biserrata leaves contains pectin can act as a substrate for the production of exo-polygalacturonase in solid-state fermentation by Aspergillus niger.