Research Interests
Microbial production and characterization of Industrial metabolites
Research is mainly focused on isolation of microorganisms for production of industrial enzymes and strain
improvement for better properties, and production, purification and characterization of these proteins. At present
the research is focused on production of pectic transeliminases (pectin lyase and pectate lyase), amylase and cellulase
(in collaboration with Dr. K. Chandraraj). These studies involve the both biochemical engineering aspects such as reactor
operation and process optimization and biochemical techniques.
Pectic transeliminases
Pectic substances are complex colloidal acid polysaccharides, with a backbone of galacturonic acid residues linked by ?-1,4-glycosidic linkages. The side chains of the pectin molecule consist of L-rhamnose, arabinose, galactose and xylose. The carboxyl groups of galacturonic acid are partially esterified by methyl groups and are partially or completely neutralized by sodium, potassium or ammonium ions. Based on the type of modifications, different pectic substances exist in nature. Pectic substances are degraded by pectolytic enzymes, which are of multiple forms and various due to complex nature of their substrates. In general, pectolytic enzymes are classified into two groups, viz., depolymerizing enzymes and saponifying enzymes. Pectic transeliminases degrade pectic substances by transelimination mechanism resulted in the formation of 4,5-unsaturated oligogalacturonates. Pectin lyase (PL) and polygalacturonate lyase (PGL) are the two important pectic transeliminases. Pectic transeliminases have potential applications in food, textile (cotton scouring) and in various other industries. Pectic transeliminases have also been applied in processing and degumming of plant bast fibres such as ramie, sun, hemp, flax and tea and coffee fermentation. Recently we isolated Candida sp. from mango fruits which is capable of producing both PL and PGL. Further studies on production and characterization of enzymes produced by Candida sp. is under progress.
Multi-enzyme production
Our long term objective is to produce ethanol from biomass. In this aspect, we are trying to develop a multi-enzyme system capable of degrading plant polysaccharides to simple sugars which can be further converted to ethanol. For this purpose we isolated a bacterial strain Bacillus sp. capable of co-producing higher levels of amylase and cellulase in nutrient medium. Interestingly, this isolate also produces amylase and cellulase in minimal medium containing glucose (without starch and CMC) suggesting that the enzymes are constitutive in nature. Identification of other enzymes produced by this isolate, optimization of the process conditions for the maximum production of multi-enzymes is under progress.
Apart from enzymes, I am also interested in process development for production of potential biopolymers (curdlan).
Curdlan production
Curdlan was discovered in 1966 at Osaka University, curdlan (common name) is an insoluble linear polysaccharide composed
of ß-1?3-linked glucose, and is synthesized by Alcaligenes species under nitrogen limiting conditions. ß-1?3-glucans are
involved in cell structure and food storage in bacteria, fungi and higher plants. Curdlan is used as a gelling material
to improve the textural quality, water-holding capacity and thermal stability of various foods such as soybean curd,
sweet bean paste jelly, boiled fish paste, noodles, sausages, jellies, and jams. Curdlan sulfate and its branch
derivatives exhibit high anti-AIDS (acquired immunodeficiency syndrome) virus activity. Linear b-1,3-glucan sulfate
has been found to have a strong inhibitory action on blood coagulation and so it can be used for the treatment of
thrombosis. Hydroxyethyl derivatives of curdlan can be used as protein drug delivery vehicles. Curdlan acts as immune
stimulator. In literature, most of the research has been done on the curdlan production by Agrobacterium species and
Alcaligenes faecalis. In order to produce curdlan with better properties, extracellular curdlan producing bacteria were
screened using aniline blue agar.
11 colonies with high blue intensities were picked and further screened based on their production in shake flasks.
Out of 11 strains, Bacillus sp.SNC 07 was found to produce curdlan in appreciable amounts. Process development for
production of higher amounts of curdlan is under progress.
Biodegradation of caffeine
Caffeine (3, 7 -dihydro -1, 3, 7 -trimethyl -1H-Purine -2, 6 dione) belongs to a group of compounds collectively known
as purine alkaloid. Chronic intake of caffeine leads to affect central nervous system and the withdrawal effects of
caffeine in humans are headache, fatigue, apathy and drowsiness. The best way to overcome the problem is to take
decaffeinated food products. The conventional methods of decaffeination are solvent extraction and supercritical
fluid extraction. These extraction methods remove other taste and aroma causing compounds from coffee and tea along
with caffeine. The use of membranes or carbon filters in caffeine removal processes will be very expensive and the
commercialization of the process becomes extremely difficult. Coffee and tea pulps are rich in nutritional compounds
such as carbohydrates and proteins, that these have a good biotechnological potential. But the presence of
anti-nutritional factors such as caffeine, tannins and poly-phenols restricts the use of coffee and tea pulps as
domestic fodder. To overcome these problems, we are trying to develop an enzymatic process to degrade specifically
caffeine. In this context, we isolated a Pseudomonas sp. from coffee cultivation area (Uthagamandalam) capable of
utilizing caffeine as sole, carbon and nitrogen source. The major metabolic pathway of caffeine degradation by this
isolate and the key enzymes involved in the degradation is yet to be identified.
Educational Background
* PhD.: Chemical Engineering (1999), Indian Institute of Technology Madras, Chennai
* M.Tech: Chemical Engineering (1996), A.C. College of Technology, Anna University, Chennai
* B.Tech: Chemical Engineering (1994), Regional Engineering College-Surathkal, Mangalore University
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