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Rajendra Kumar Saxena 

Professor
(Retired on 31st Dec, 2015, after serving the Department for 31 years)

Department of Microbiology
Bachhawat Block, First Floor
University of Delhi South Campus

Ph: 011-24157169
Email: rksmicro@yahoo.co.in 
CV (Download pdf file)
  Education
BSc (1969), University of Sagar, Sagar
MSc (1971), University of Sagar, Sagar
PhD (1977), University of Delhi, Delhi
Description of Research Expertise

Research interest:
Microbial physiology and biochemistry
Applied and Industrial Microbiology, Microbial Enzymes, Biotransformations
Production of Bioactive molecules / biofuels / sugar alcohols and bacterial cellulose.
Liposome technology and its applications in drug delivery system
Microbial Differentiation
Cyanobacterial Metabolism

Key words: Industrial enzymes, biotransformation, biofuels, bioremediation, sugar alcohols, organic acids, bacterial cellulose


Description of Research:

I have been working in the field of microbiology and biotechnology for the last forty years at the Department of Microbiology University of Delhi South Campus (UDSC). During this period, I have been involved in teaching, research and administrative responsibilities. Earlier, I carried out my Ph.D programme (1971-1977) at Botany Department, Delhi University in the field of microbial physiology, biochemical genetics and industrial microbiology. Immediately after this, I started teaching botany at undergraduate level in one of the university college. Subsequently, in 1981, I got the opportunity to visit Japan as a post doctoral fellow. This was followed by many scientific assignments abroad and I visited England (1986), Germany (1990), USA (1995 & 2007), Russia (1999, 2010, 2011, 2012),  China (2000 & 2008), Belgium (2005), Denmark (2005), Netherlands (2005), Italy( 2005 & 2007), Japan (2005), Nepal (2007), Dhaka, Bangladesh (2011) and Paris, France (2013).

In 1984-85, I established the Department of Microbiology in University of Delhi at South Campus. Once, I established my own laboratory in the Department at UDSC having expertise in different fields of microbiology such as microbial physiology, biochemistry and regulation, industrial microbiology, bioming & bioremediation and membrane regulation, I initiated my research work in these disciplines.

 

Below is a brief summary of my research interests and achievement.

  1. Differentiation in filamentous fungi under batch fermentation was thought to be inhibited, however, our report as early as in 1973 published in J. Gen. Appl. Microbiol. became a leading paper investigating asexual differentiation under batch fermentation processes. Since then, we have not only investigated asexual differentiation but the concept of microcycle conidiation where a conidium directly germinates into an asexual fruiting body without any intervening vegetative phase gave a lead to investigate the biochemical and molecular regulatory processes involved during the process of asexual differentiation in fungi. This is well elaborated from our series of publications.

  2. My research interest in industrial microbiology lies in enzymes, primarily the commercially important hydrolases like lipases, proteases (rennets and alkaline Proteases like subtilisin), amylases, tannases, asparaginases, laccases and chitinases. Our achievements on enzyme research are as follows:

  3. I have been working on different aspects of microbial lipases for the past 20 years and have successfully achieved the process optimization of lipases from fungal species like Aspergillus terreus, A.carneus, Fusarium globulosum, Penicillium sp., Thermomyces lanuginosa and bacteria like Pseudomonas aeruginosa, Bacillus subtilis and Bacillus stearothermophilus. Lipases from these organisms show novel properties of pH & temperature tolerance and stability, regio-specificity and chemo- and regio-selective hydrolysis of pharmaceutically important polyphenolic compounds. Besides this, some have even shown their industrial significance by playing a critical role in the synthesis of cardiovascular drugs and nucleoside analogs. The production process has been optimized and scaled up to a pilot plant. Cost effective and fast purification procedures for downstream processing have been developed and optimized. These lipases have been characterized and evaluated for several industrially important reactions. Economically viable processes have been developed for immobilization of these lipases. Binary immobilization using covalently linked crystal aggregates has been carried out for Thermomyces lanuginosa lipase/s. Synthesis of cocoa butter and other industrially significant esters of fatty acids have been optimized using these lipases which are of immense importance for industries. With proteases we have achieved excellent industrially important results. One of our own indigenous bacterial isolate produces an alkaline protease at very high titres with excellent dehairing potential. This property is of great importance for tanneries as these are a major source of pollution due to the chemicals used in leather processing. However, this protease has the capacity to carry out dehairing without use of any chemical/s within 8-12h. This process has been demonstrated at a commercial scale to tanneries. Also using proteases, we have been able to make amino acid supplements, which can be used to add nutritive value to animal feed and nutraceuticals.

  4. Recently, we have carried out investigations on rennet production from a bacterial source. Rennets are a very important class of enzyme which is used in the manufacture of cheese. We have optimized the production of this enzyme to a 300L fermentor size. Successful use of this rennet in making Mozarella cheese has been carried out. We have successfully investigated an antistaling α--amylase for prolonging the shelf life of breads, buns and other baked products. The patent for this application has been obtained. We have already got nine patents and others are in process. Presently, we are in a position to transfer some of our enzyme technologies to industries. Specific plate assay procedures for massive screening programmes for industrially important enzymes like tannases and L-asparaginases have been developed. These procedures are widely used by researchers in this field.

  5. Considerable work has been done in my laboratory on tannases, which find applications in gallic acid production, trimethoprim synthesis, animal feed improvement and instant tea manufacture. We are currently investigating a few good L-asparaginase producers. In addition, the use of this enzyme as anti cancer agents and reduction of acrylamide deposition in fried fast foods is being investigated and a good success has been achieved. While working with fermentation for enzyme production, good success has been achieved in the utilization of the microbial biomass. Initially, we could successfully purify the enzyme chitinase as well as the chitin residues of the mycelial walls, which was subsequently developed as a bioindicator of heavy metal contamination. In addition, the chitin obtained from Aspergillus terreus and A. carneus was successfully developed as a metal biosorbent for removal of heavy metals from industrial effluents and mine wastes. Laccase from Aspergillus nidulans having utility in the decolorization of dyes in effluents is well studied and evaluated.

  6. The studies on biomining were extended and successful processes have been developed using fungi (Apsergillus japonicus and Trichoderma viride) and blue green algae (Oscillatoria spp.) where we have optimized and examined that these organisms can be made to accumulate heavy metals upto one fourth of their weight. Immobilization of these organisms as whole cells, developing of bioindicator sensors/filters and recycling of these organisms for effluent treatment have successfully been achieved. We have also successfully investigated and worked out the extraction of copper from ferro-mangenese sea nodules from Indian Ocean basins using A.japonicus where 85% of the metal could be extracted within 72 hours. We have been collaborating on this aspect of research with Hindustran Zinc Ltd., Udaipur and National Metallurgical Laboratory Jameshedpur.

  7. In the trafficking of molecules across the cell membrane, an event which is of utmost importance we have successfully shown that the major amount of the membrane protein (porins) are under the influence of the membrane liopolysaccharides (LPS) in which they are embedded. We have developed and optimized production processes from 10 to 300 L bioreactor. The most economical production strategies have been devised along with several fed batch strategies to enhance yields. Large scale purification of fermentation broths containing enzymes has been successfully achieved using the aqueous two phase system involving PEG and phosphate. This process is very rapid, easy and efficient and cost effective for large scale operations. Also, other downstream processes which are cheap and economically viable have been developed.

  8. We have also worked and developed a process for the production of xylitol, a sweetner, which finds use as a sugar substitute and in the treatment of dental caries. We have developed production protocols for efficient conversion of hemicellulose into xylitol. Purification strategies have also been worked out for this important carbohydrate molecule Similarly another sweetner erythritol has also been worked out. Production of industrially important organic acids such as succinic, citric, lactic and shikimic acids has also been an area of interest and investigation. Here, we developed expertise in both aerobic and anaerobic fermentation processes for their production.Another important product of anaerobic fermentation is the production of 1,3 propanediol from glycerol. We have been successful in not only obtaining high yields but also in efficient purification protocol has been developed and have applied for the patent.

  9. Work on biodiesel is a relatively new development in my laboratory. We have achieved some good and promising results in synthesis of biodiesel using lipases from our laboratory. Recently, work on microbial cellulose production has been initiated in our laboratory. According to the literature reports, cellulose obtained from microbes (bacteria) is better than the plant cellulose in certain aspects especially with respect to properties and applications. Microbial has certain unique properties such as high purity, ultra fine structure, excellent mechanical strength, high water holding capacity, biodegradability, high degree of polymerization and crystallinity. Due to these unique properties, microbial cellulose has potential applications targeting various industries particularly having its immense importance in medical field. Wherein; it can be used as wound dressings or bandages for healing wound, making artificial skin, artificial vessels etc.

 

 

Lab Personnel

Publications: Search Pubmed for publications (click here). Select publications have been listed below.

S.No

Title

 Name of the Journal

IF

Year

1

Dual substrate strategy to enhance butanol production using high cell inoculum and its efficient recovery by pervaporation

Journal of Bioresource Technology

http://dx.doi.org/10.1016/j.biortech.2013.11.022

5.039

2014

2

 Enzyme mediated beam house operations of leather industry: a needed step towards greener technology

Journal of Cleaner Production

http://dx.doi.org/10.1016/j.jclepro.2013.04.017 

3.590

2013

3

Expanding horizons of shikimic acid. Recent progresses in production and its endless frontiers in application and market trends

Applied Microbiology and Biotechnology

DOI 10.1007/s00253-013-4840-y

3.811

2013

4

Evaluation of corncob hemicellulosic hydrolysate for xylitol production by adapted strain of Candida tropicalis

Journal of carbohydrate polymers

http://dx.doi.org/10.1016/j.carbpol.2012.11.033

3.916

2012

5

Bacillus sphaericus: the highest bacterial tannase producer with potential for gallic acid synthesis.

Journal of Bioscience and Bioengineering

doi:10.1016/j.jbiosc.2011.02.008

1.869

2011

6

Microbial production of 1,3-propnediol: Recent development and emerging opportunities

Journal of   Biotechnology Advances

http://dx.doi.org/10.1016/j.biotechadv.2009.07.003

8.905

2009

7

Role of casein on induction of a milk clotting protease from an indigenously isolated Bacillus subtilis.

Letters  of   Applied Microbiology

doi: 10.1111/j.1472-765X.2008.02324

2.386

2008

8

Statistical optimization for succinic acid production from E. coli in a cost effective medium

Applied  Biochemistry and  Biotechnology

DOI 10.1007/s12010-007-0014-7

1.687

2007

9

Modification of the porin function by the membrane components used for the reconstitution of model  membranes.

Current Microbiology

DOI: 10.1007/BF01568940

1.359

1989

10

Conidiation of Aspergillus nidulans in submerged liquid culture

Journal of General. Applied Microbiology

http://dx.doi.org/10.2323/jgam.19.141

0.74

1973

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