Studies on the effect of different bioprocess parameters on pectinase production by aspergillus niger

Abstract

Pectinase is heterogeneous group of enzymes that have a polysaccharides substrate and breaks down the pectin component, which found in the plant cell wall, into simple sugar and galacturonic acid. The breaks down of the pectin will cause the plant tissues to undergo some modification on its cell wall, or other activities such as maceration or cell lysis. The pectinases or usually known as pectinolytic enzymes were extensively used in food industries that involve degradation of plant materials to fasten the fruit juice extraction process. Among different biofactories of pectinases, filamentous fungi such as Aspergillus niger were the best known for the production and secretion of pectinase. Therefore, the objective of this research was to develop industrial culture medium and a cultivation strategy for the production and secretion of pectinases in a semi-industrial scale by A. niger. In this study, the effect of medium composition on the production and secretion of pectinase was studied through the classical method where the medium screenings were done initially to find the best medium for the production of pectinase. The optimized medium through classical method were pectin industrial (30 g L-1), ammonium sulphate (3.33 g L-1), di-potassium hydrogen phosphate (1 g L-1), magnesium sulfate heptahydrate (0.05 g L-1), potassium chloride (0.05 g L-1) and iron sulphate heptahydrate (0.1 g L-1). Following this step, medium optimization was carried out using statistical approach and the optimized medium were pectin industrial (32.22 g L-1), ammonium sulphate (4.33 g L-1), di-potassium hydrogen phosphate (1.36 g L-1), magnesium sulphate heptahydrate (0.05 g L-1), potassium chloride (0.05 g L-1) and iron sulphate heptahydrate (0.1 g L-1). Therefore, the result of pectinase production for optimized medium was 64.83 % higher compared to unoptimized medium. Next, the effect of processing parameters which was pH condition (controlled pH at 5.5 and uncontrolled pH) was studied in the batch fermentation. The pectinase production of controlled pH was 51.35 % higher compared to the uncontrolled pH. However, the selection of the best condition for fed-batch fermentation was uncontrolled pH due to the low costing during the cultivation. Finally, the fed-batch strategies for full media and monocorbon were studied and the best feeding strategies was from the monocarbon feeding due to the higher prectinase yield with 429.95 U mL-1 compared to the full media feeding with 138.27 U mL-1. Thus, these all together lead to the development of industrial process for pectinase production in semi-industrial scale.