Utilizing Aspergillus niger in industrial production of pectinase

By Labake Ikuomola

In recent years, considerable attention has been paid to the use of microorganisms in industrial fermentation processes, especially enzyme production. There has been a huge interest in growing fungi having the ability to produce pectinase, an enzyme which degrade pectin, which can be used in industrial fruit processing.

Pectin is an heteropolysaccharide present in the cell wall of terrestrial plant.During this processing, they play a crucial role in the extraction and clarification of fruit juice. In order to obtain concentrates of high quality, it is essential to degrade pectin using pectinolytic enzymes, hence clarifying the juice.

Microbial enzymes are commercially produced either through solid substrate fermentation or submerged fermentation. These techniques for enzyme production are generally conducted in stirrer tank reactors under aerobic conditions using batch or fed-batch system. Solid substrate fermentation (SSF) incorporate microbial growth and product formation on or within particles of a solid substrate under aerobic conditions, in the absence or near absence of free water, and does not generally require aseptic conditions for the enzyme production.

Submerged fermentation (SMF), on the other hand, simply refers to cultivation of microorganisms in liquid broth, requiring high volume of water, continuous agitation and prompt removal of the large effluent generated. However, high capital investment, energy costs and infrastructural requirements for large scale production of enzymes make the application of SMF method impracticable in most developing countries.

It has been well documented that pectinolytic enzymes produced by certain sprouting strains of fungi like Aspergillus niger, Aspergillus oryzae and Rhizopus oryzae have been utilized in fruit clarification process because of their desirable characteristics. However, these fungal strains have not been exploited to scale up the production of these enzymes for purification and immobilization.

Aspergillus niger produces pectinases together with cellulases and xylanases. Thus, this fungus produces the full compliment of enzymes required for the hydrolysis of pectinolytic biomass. This explains why the fungus thrives on waste plant matters and is capable of utilizing carbon sources in its culture media.

The important industrial uses of pectinases should drive up the need for further production using this fungus. Among the uses are the aforementioned extraction, clarification and liquefaction of fruit juices and wine as well as for improving flavour of black tea.

Uses in the fabric industries include:

• for setting of plant fibres such as flax, hemp and jute;
• for biopreparation of  cotton fabrics;

Uses in the paper industries include:

• for enzymatic polishing of jute/cotton blended fabrics in the paper industry;
• to solve the retention problems in mechanical pulp bleaching
• for treatment of pulp and paper effluents.