Characterization and wash performance analysis of microbial extracellular enzymes from East Calcutta Wetland in India

American Journal of Applied Sciences, Dec, 2008 by Ramesh Malathu, Sanhita Chowdhury, Madhusmita Mishra, Sumana Das, Prabhat Moharana, Joydeep Mitra, Ujjal K. Mukhopadhyay, Ashoke Ranjan Thakur, Shaon Ray Chaudhuri

INTRODUCTION

Currently enzymes have attracted the attention of the world over due to their wide range of industrial applications in many fields including organic synthesis, clinical analysis, pharmaceuticals, detergents, food production and fermentation. Enzymes are gradually replacing the use of harsh chemicals in various industrial processes. Since they work under moderate conditions, such as warm temperatures and neutral pH they reduce energy consumption by eliminating the need to maintain extreme environments, as required by many chemically catalyzed reactions. The reaction specificity of the enzymes lead to minimization of the production of by-products and thereby the application of enzymes offer minimal risk to the environment.

Approximately eighty percent of all industrial enzymes are hydrolytic in nature and are used for depolymerization of natural substances i.e. the breaking down of complex molecules into simpler ones. Of these enzymes, sixty percent are proteolytic enzymes used by the detergent, dairy and leather industries (1). Enzymes have been known to be used for improving the cleaning efficiency of detergents and are now well accepted as ingredients in powder as well as liquid detergents and industrial/ institutional cleaning products. Detergent enzymes account for about 30% of the total worldwide enzyme production and represent one of the largest and most successful applications of modern industrial biotechnology (2). The performance of enzymes in detergents depends on a number of factors, viz the detergent's composition, type of stains to be removed, wash temperature, washing procedure and wash-water hardness. Besides high temperature and alkalinity, the enzyme often must withstand the presence of detergent additives such as bleaching agents, bleach activators, surfactants, perfumes etc. Out of the vast pool of enzymes, proteases from micro organisms are the most widely exploited enzymes in detergent industries (3) They can act as minor additives or can become key ingredients in detergents. These enzymes hydrolyze protein based stains in fabrics into soluble amino acids. Among the various proteases, bacterial proteases are the most significant, compared with animal and fungal proteases. Bacterial proteases are mostly extracellular, easily produced in large amount and are often thermostable and active at wider pH range. Alkaline proteases from various strains of Bacillus sp. have been reported(4-6). There are quite a few patents of enzymatic detergent additive (European Patent EP0581839, United States Patent 4810414). Protease from Nocardiopsis sp. as well as Pseudomonas aeruginosa have also been reported to work as an additive to detergent (7-9). One important factor to be considered during the selection of the enzyme is its stability and the shelf life of the enzymatic action. For industrial applications, the immobilization of enzyme on a solid support can offer additional advantages like repeated use of the enzyme, ease of product separation and improvement in stability (10).

To improve washing efficiency currently available detergents usually contain enzymes like amylase, cellulase and lipase. Amylase catalyzes the break down of starch based stains into smaller segments of oligosaccharides and dextrins which are water soluble. Lipase is used in detergent formulations to remove fat containing stains such as those resulting from frying fats, butter, salad oils etc. The enzyme hydrolyzes triglycerides into mono and diglycerides, glycerol and free fatty acids which are more soluble than fats. Lipases from different species of Pseudomonas and Acinetobacter have been reported to be used in detergent formulations (11).

Keeping in view the diverse potential of the microbial enzymes, the present study was focused on the characterization and wash performance of detergent compatible protease and lipase from different bacterial isolates obtained from East Calcutta Wetland which is a biodiversity rich ecosystem of Calcutta. The location of this vast low lying area is such that the entire city's waste is drained into it. It in turn act as a sewage treatment plant (12). The waste dumped into this system is further purified and recycled in activities like agriculture and pisciculture thereby generating products, economy and employment (13-14). The purification of the waste, mostly heavy metals, is found to be a combined effort of diverse groups of planktons, water hyacinth and microbes (15-16). Previous studies on microbial resource mapping of this area have revealed the existence of microbes belonging to 12 main bacterial phyla (17). In that study, certain clones were found to be similar to Streptococcus macedonicus and Acinetobacter lowffi which are known to produce extracellular protease(s) and lipase(s) respectively. The growth conditions of these microbes were replicated in the laboratory to cultivate microbes from environmental samples of East Calcutta Wetland having potential of producing extracellular protease and lipase. Out of 21 isolates obtained, two were selected, one secreting protease and the other lipase with an aim to use the extracellular enzymes as additives to standard detergents.