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Articles by Arijit Das
Total Records ( 6 ) for Arijit Das
  Sourav Bhattacharya and Arijit Das
  Lactic Acid Bacteria (LAB) predominates the micro flora of fermented products. They produce metabolites that inhibit the growth of food-borne pathogens and spoilage microorganisms. The objectives of the present study were isolation, identification of LAB from traditional Indian fermented foods and study of physical and cultural parameters on the bacteriocins produced by them. Seven isolates of bacteriocin producing LAB were isolated from curd, dosa batter and idli batter and were identified as species of Lactobacillus. The culture supernatants of the seven isolates were evaluated for their antimicrobial activity against pathogens like Staphylococcus aureus and Pseudomonas sp. The stability of the bacteriocins was tested at different temperatures, pH, presence of bile salt like sodium deoxycholate and storage period at 4°C. The diameters of the inhibitory zones ranged between 9 and 12 mm for Staphylococcus aureus, with no effect on Pseudomonas. The bacteriocins produced by the isolates were stable at temperatures ranging between 30 to 80°C and over a wide range of pH from 2 to10, with the highest activity at pH 6. It was also found that the bacteriocins were stable at different concentrations of the bile salt used and remained active even after a storage period of 30 days at 4°C. Sodium Dodecyl Sulphate polyacrylamide gel electrophoretic analysis of the partially purified bacteriocins suggested their apparent molecular weights between 16.5 to 48 kDa. These bacteriocins may have a potential use as food biopreservatives and may help in improving the gut environment by combating several pathogenic microorganisms.
  Mahadevan M. Sundar , Nagananda G.S. , Arijit Das , Sourav Bhattacharya and Sandeep Suryan
  Bacteriophages have been found to be effective against a wide variety of pathogenic bacteria as they are highly host specific. The present study describes the isolation of bacteriophages effective against few human pathogens such as Salmonella typhi, Escherichia coli and Pseudomonas aeruginosa. A total of five isolates of bacteria were obtained from the sewage water, sampled from the sewage treatment plant located at Jinke Park, Bangalore, India. Based upon the colony morphology, biochemical characterization and growth on selective media, the isolates were identified as Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Klebsiella species and Shigella species. Out of the five different isolates three were sensitive to bacteriophages. The sensitive cultures belonged to the genera Salmonella typhi, Escherichia coli and Pseudomonas aeruginosa. The phage filtrates, when spotted onto the lawn cultures of the respective host bacterium, resulted in the development of clear zones indicating the presence of lytic bacteriophages against the host bacteria. It was also found that each of the phages for E. coli and Salmonella typhi was only able to infect its original host bacterium, whereas, the phage for Pseudomonas aeruginosa was able to infect both Pseudomonas and E. coli. Studies of the morphology and characterization of these phages are currently being conducted. These isolated phages may hold a lot of promise as the first choice of prophylaxis (Phage Therapy) against nosocomial and secondary infections by deadly multi-drug resistant bacteria in the near future.
  G.S. Nagananda , Arijit Das , Sourav Bhattacharya and T. Kalpana
  Biofertilizers are the formulations of living microorganisms, which are capable of fixing atmospheric nitrogen in the soil and thereby, increasing the crop yield. Trigonella foenum-graecum L. is a medicinally important plant possessing anti-diabetic, anti-cancerous, anti-microbial and hypocholesterolaemic properties. The present study was conducted to develop an in vitro method for studying the effects of biofertilizers (Azotobacter and Rhizobium) on the seed germination and development of Trigonella foenum graecum L. using a simple and cost-effective liquid culture medium containing glass marbles as reusable and biologically inert support matrix. Sucrose optimization studies revealed maximum development for the plantlets grown on 1X Murashige and Skoog liquid medium containing 4% sucrose and glass marbles. Azotobacter and Rhizobium were isolated from rhizosphere soil and root nodules of Trigonella plants, respectively and identified following the standard procedures. Mass cultivation of the bacteria carried out for 5 days reported counts of 2.3x104 cells mL-1. The harvested bacterial cells were used to coat the seeds in the presence and absence of charcoal. After 15 days of growth under in vitro conditions, the root length, shoot length, fresh weight, protein, carbohydrate and chlorophyll contents of the plantlets were determined. Maximum growth was observed for the plantlets grown on 1X MS medium with 4% sucrose and glass marbles, inoculated with 40% concentration of Azotobacter, Rhizobium and their co-inoculum mixed with charcoal. Field trials, conducted under green house conditions, revealed that 10% biofertilizer co-inoculum supported maximum growth of the plants when the seeds were coated with charcoal.
  Arijit Das , G.S. Nagananda , Sourav Bhattacharya and Shilpi Bhardwaj
  Microbial contamination of ready-to-eat foods and beverages sold by street vendors and hawkers has become a global health problem. Street vended chaats like panipuri and bhelpuri sold in almost all the cities throughout India are consumed by huge population of people. The present study was undertaken to investigate the microbiological quality of street foods like panipuri and bhelpuri sold in many parts of Bangalore, India. Eight different samples of these chaats were aseptically collected from four locations of Bangalore City. The samples were analyzed within an hour of procurement. Isolation, enumeration and identification of the prevalent bacteria and fungi were carried out following the standard procedures. Analysis of the food samples revealed high loads of bacterial pathogens such as Streptococcus faecalis, Escherichia coli, Staphylococcus aureus, Bacillus sp., Klebsiella sp. and Pseudomonas sp. Total viable counts of bacteria in all the samples varied between 0.4-3.0x104 cfu g-1, faecal coliforms between 0.03-0.14x104 cfu g-1 and faecal streptococci between 0.2-11x104 cfu g-1. Aciduric yeasts like Saccharomyces and filamentous fungi like Mucor and Rhizopus were also encountered. Salmonella and Vibrio cholerae were not detected in any of the samples. The presence of faecal streptococci and coliforms indicated faecal contamination of the processing water as well as the prevailing unhygienic conditions related to the location of the food stalls. It is suggested that regular monitoring of the quality of street foods must be practised to avoid any food-borne pathogenic outbreaks in future.
  Mahdi Eskandarian Boroujeni , Arijit Das , K. Prashanthi , Sandeep Suryan and Sourav Bhattacharya
  Actinomycetes constitute an economically important class of bacteria for their ability to produce various degradative enzymes and secondary metabolites. The present study was conducted with the objectives to isolate some soil actinomycetes, screen them for production of hydrolytic enzymes and characterize them. A total of 30 isolates of actinomycetes were obtained from six soil samples collected from Kuruva Island and the banks of Pookot Lake from Wayanad district in Kerala, India. Screening for enzyme production among 18 randomly selected isolates revealed that 13 of them were able to synthesize either cellulase, pectinase and/or xylanase. The results indicated that 44.4% of the total isolates produced all the three enzymes. Based on morphological and biochemical characterization, the active isolates were found to belong to the genus Streptomyces. The relatedness between the 13 active isolates was determined by RAPD fingerprinting using 20 different primers. Only amplification with primer OPAB-9 resulted in good scorable bands and revealed a prominent band at 600 bp in 54% of the isolates. The dendrogram showed that the active isolates fell into one super cluster which further consisted of three clusters and one out group. The presence of identical cultural characteristics was detected in most of the clusters. With respect to the enzyme activity, the similarity was only noticed among majority of the members of cluster 1. This molecular study may be employed as an effective tool to characterize streptomycete isolates capable of producing various industrially important enzymes.
  Jigita Padhiar , Arijit Das and Sourav Bhattacharya
  The present study was aimed at optimization, production and partial purification of lipases from Pseudomonas aeruginosa, Candida albicans and Aspergillus flavus. Various nutritional and physical parameters affecting lipase production such as carbon and nitrogen supplements, pH, temperature, agitation speed and incubation time were studied. Refined sunflower oil (1% v/v) and tryptone at a pH of 6.2 favored maximum lipase production in Pseudomonas at 30°C and 150 rpm, when incubated for 5 days. In C. albicans refined sunflower oil (3% v/v) and peptone resulted in maximum lipase production at pH 5.2, 30°C and 150 rpm, when incubated for 5 days. In A. flavus coconut oil (3% v/v) and peptone yielded maximum lipase at pH 6.2, 37°C, 200 rpm after an incubation period of 5 days. The lipases were partially purified by ammonium sulphate precipitation and dialysis. In P. aeruginosa enzyme activity of the dialyzed fraction was found to be 400 U mL-1 and for C. albicans 410 U mL-1. The dialysed lipase fraction from A. flavus demonstrated an activity of 460 U mL-1. The apparent molecular weights of the dialyzed lipases were determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The dialyzed lipase fraction obtained from P. aeruginosa revealed molecular weights of 47, 49 and 51 kDa, whereas, lipases from C. albicans and A. flavus demonstrated 3 bands (16.5, 27 and 51 kDa) and one band (47 kDa), respectively. These extracellular lipases may find wide industrial applications.
 
 
 
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