Abhijit Chowdhury

Nucleic acid amplification: Alternative methods of polymerase chain reaction.

Nucleic acid amplification is a valuable molecular tool not only in basic research but also in application oriented fields, such as clinical medicine development, infectious diseases diagnosis, gene cloning and industrial quality control. A comperehensive review of the literature on the principles, applications, challenges and prospects of different alternative methods of polymerase chain reaction (PCR) was performed. PCR was the first nucleic acid amplification method. With the advancement of research, a no of alternative nucleic acid amplification methods has been developed such as loop mediated isothermal amplification, nucleic acid sequence based amplification, strand displacement amplification, multiple displacement amplification. Most of the alternative methods are isothermal obviating the need for thermal cyclers. Though principles of most of the alternate methods are relatively complex than that of PCR, they offer better applicability and sensitivity in cases where PCR has limitations. Most of the alternate methods still have to prove themselves through extensive validation studies and are not available in commercial form; they pose the potentiality to be used as replacements of PCR. Continuous research is going on in different parts of the world to make these methods viable technically and economically.

Critical Factors Affecting the Success of Cloning, Expression, and Mass Production of Enzymes by Recombinant E. coli

E. coli is the most frequently used host for production of enzymes and other proteins by recombinant DNA technology. E. coli is preferable for its relative simplicity, inexpensive and fast high-density cultivation, well-known genetics, and large number of compatible molecular tools available. Despite all these advantages, expression and production of recombinant enzymes are not always successful and often result in insoluble and nonfunctional proteins. There are many factors that affect the success of cloning, expression, and mass production of enzymes by recombinant E. coli. In this paper, these critical factors and approaches to overcome these obstacles are summarized focusing controlled expression of target protein/enzyme in an unmodified form at industrial level.

Screening of Lactobacillus spp. from Buffalo Yoghurt for Probiotic and Antibacterial Activity

Since the beneficial effects of viable probiotic bacteria as dietary supplements have gained huge research interest, Lactobacillus spp. with probiotic characteristics are widely used to prepare fermented dairy products such as yoghurts, milk-shakes etc. In this study, eight (08) homemade yoghurt samples were collected from different regions in the country for isolation of probiotic Lactobacillus spp. Among the samples, four (04) isolates were identified as Lactobacillus plantarum based on their growth and biochemical characteristics. The Isolates were resistant to NaCl (1-9%) and bilesalt (0.05-0.3%) and showed good growth in the acidic condition, while maximum growth was observed at pH around 6.0. The isolates were examined for their antibacterial activity against nine (09) different test pathogens and found all pathogens are inhibited their growth to some extent but maximum zone of inhibition was observed against Bacillus cereus (53.20 mm) and minimum was against Staphylococcus aureus (19 mm) after 72 hour incubation. The results of the present study indicate that, homemade yoghurts in Bangladesh are potential source of probiotic Lactobacillus spp. Further extensive research on isolation and characterization of probiotic organisms from local fermented foods and their growth optimization might be required for development of probiotic enriched food supplements in our country.