Isolation, Identification and Optimization of Culture Conditions of Bacillus sp. Strain PM1 for Alkalo-thermostable Amylase Production.

Aims: To isolate and optimize the culture conditions for thermo stable and alkaline amylase production from bacteria. Study Design: Optimization of different physiological and nutritional parameters for amylase production and kinetic studies of amylase. Place and Duration of Study: Soil Samples: Herbal garden of Amity University Haryana, Gurgaon (Manesar), India, between April 2012 and September 2012. Methodology: Amylolytic isolates were selected by flooding the nutrient agar plates containing 2% starch with Lugol solution. Isolates were selected on the basis of higher ratio of clear zone to colony size and grown in nutrient broth containing 2% starch. The level of amylase was detected in the culture filtrate. The selected isolate showing maximum amylase production was identified on the basis of 16S rDNA amplification. Results: An Alkalo-thermostable amylase producing bacterial isolate from soil was identified as Bacillus sp. strain PM1 on the basis of 16S rRNA. It yielded 3.5 U/ml of amylase in medium containing (%) starch 2.0, beef extract 0.5, NaCl 0.5 at 50ºC, pH 7.0 at 180 rpm after 72 h. The optimum pH and temperature for amylase activity was 8.0 and 50°C, respectively. The enzyme exhibited 67% activity after 60 minute incubation at 50ºC. At pH 8.0, the enzyme retained 78% activity after 4 h. Conclusion: The properties of the isolated enzyme are adequate for its use in starch processing and baking industry.

Isolation and Identification of Xylanolytic Enzyme from an Effective Strain Bacillus Licheniformis Isolated from the Decaying Wood.

A new species of Bacillus licheniformis produced extracellular xylanase under submerged fermentation when wheat bran is used as carbon source. The xylan is the most common hemicellulosic polysaccharide in food industry and agricultural wastes, comprising a backbone of xylose residues linked by β-1,4 glycosidic bonds. Bacillus licheniformis has been shown to be a promising organism for enhanced production of xylanases & β-xylosidase under submerged fermentation (SmF). The optimization of cultural conditions and carbon, nitrogen sources for enzymes production. The bacterial strain Bacillus licheniformis was cultivated using as substrate xylan, wheat bran, corn straw, corncob, and sugarcane bagasse. Wheat bran has been a good xylanase (16.8U/ml) & β xylosidase (5.6U/ml) activity after 48h of fermentation. Maximum enzyme activity was observed in xylan as carbon source and peptone as nitrogen source. Both crude enzymes were characterized and a bacterial xylanase shows optimum pH for xylanase activity at 6.5 & β xylosidase were found to be 6.0. The optimum temperatures were 450C for both and they were thermally stable up to 500C. The parameters of Vmax and Km obtained using Line weaver-Burk plot method were 277.7μmol / min/mg and 5.26 mg /L correspondingly.

Small but mighty RNA-mediated interference in plants.

RNA silencing is a conserved phenomenon of regulation of gene expression by small RNAs derived from cleavage of double-stranded RNA (dsRNA). The present review deals with three overlapping modes of small RNA-mediated silencing particularly in plants. In case of post-transcriptional gene silencing (PTGS), Dicer, an endonuclease, cleaves dsRNA to produce approximately 21nt-long small interfering RNAs (siRNAs), which guide RISC, another nuclease complex, to destroy specific target mRNAs based on sequence complementarity with the siRNA. Another class of siRNAs of 25nt-long is also produced from dsRNA by Dicer, different from that generates 21nt-long siRNA. These longer siRNAs are probably involved in systemic silencing during PTGS and guide methylation of both DNA and histone, and induce heterochromatinization and consequent transcriptional repression of the targeted gene. Both siRNA-mediated PTGS and epigenetic modification of the genome are considered as defense mechanisms to protect against invading viruses, transposons or aberrantly expressing transgenes. Regulation of expression of endogenous genes is mediated by another class of 21nt-long small RNAs called microRNAs (miRNA). Genes encoding the miRNAs are present either in the intergenic regions, introns or coding regions of the plant genome. Cleavage of a stem-loop precursor transcript called pre-miRNA, by another class of Dicer generates miRNAs, which in association with nuclease complex similar to RISC, if not identical, either degrade target mRNA or cause translational repression. The applications of RNA silencing in functional genomics and crop improvement are discussed.