Anita Chaudhary

Bioprospecting thermophiles for cellulase production: a review

Most of the potential bioprospecting is currently related to the study of the extremophiles and their potential use in industrial processes. Recently microbial cellulases find applications in various industries and constitute a major group of industrial enzymes. Considerable amount of work has been done on microbial cellulases, especially with resurgence of interest in biomass ethanol production employing cellulases and use of cellulases in textile and paper industry. Most efficient method of lignocellulosic biomass hydrolysis is through enzymatic saccharification using cellulases. Significant information has also been gained about the physiology of thermophilic cellulases producers and process development for enzyme production and biomass saccharification. The review discusses the current knowledge on cellulase producing thermophilic microorganisms, their physiological adaptations and control of cellulase gene expression. It discusses the industrial applications of thermophilic cellulases, their cost of production and challenges in cellulase research especially in the area of improving process economics of enzyme production.

Bacterial and Archaeal Phylogenetic Diversity of a Cold Sulfur-Rich Spring on the Shoreline of Lake Erie, Michigan

ABSTRACT Studies of sulfidic springs have provided new insights into microbial metabolism, groundwater biogeochemistry, and geologic processes. We investigated Great Sulphur Spring on the western shore of Lake Erie and evaluated the phylogenetic affiliations of 189 bacterial and 77 archaeal 16S rRNA gene sequences from three habitats: the spring origin (11-m depth), bacterial-algal mats on the spring pond surface, and whitish filamentous materials from the spring drain. Water from the spring origin water was cold, pH 6.3, and anoxic (H2, 5.4 nM; CH4, 2.70 μM) with concentrations of S2− (0.03 mM), SO42− (14.8 mM), Ca2+ (15.7 mM), and HCO3− (4.1 mM) similar to those in groundwater from the local aquifer. No archaeal and few bacterial sequences were >95% similar to sequences of cultivated organisms. Bacterial sequences were largely affiliated with sulfur-metabolizing or chemolithotrophic taxa in Beta-, Gamma-, Delta-, and Epsilonproteobacteria. Epsilonproteobacteria sequences similar to those obtained from other sulfidic environments and a new clade of Cyanobacteria sequences were particularly abundant (16% and 40%, respectively) in the spring origin clone library. Crenarchaeota sequences associated with archaeal-bacterial consortia in whitish filaments at a German sulfidic spring were detected only in a similar habitat at Great Sulphur Spring. This study expands the geographic distribution of many uncultured Archaea and Bacteria sequences to the Laurentian Great Lakes, indicates possible roles for epsilonproteobacteria in local aquifer chemistry and karst formation, documents new oscillatorioid Cyanobacteria lineages, and shows that uncultured, cold-adapted Crenarchaeota sequences may comprise a significant part of the microbial community of some sulfidic environments.

Optimization of fermentation conditions for cellulases production by Bacillus licheniformis MVS1 and Bacillus sp. MVS3 isolated from Indian hot spring

The aim of this work was to study the effect of some nutritional and environmental factors on the production of cellulases, in particular endoglucanase (CMCase) and exoglucanases (FPase) from Bacillus licheniformis MVS1 and Bacillus sp. MVS3 isolated from an Indian hot spring. The characterization study indicated that the optimum pH and temperature value was 6.5 to 7.0 and 50-55°C, respectively. Maximum cellulases production by both the isolates was detected after 60 h incubation period using wheat and rice straw. The combination of inorganic and organic nitrogen source was suitable for cellulases production. Overall, FPase production was much higher than CMCase production by both of the strains. Between the two thermophiles, the cellulolytic activity was more in B.licheniformis MVS1 than Bacillus sp. MVS3 in varying environmental and nutritional conditions.

Levanases for control of slime in paper manufacture

Abstract Formation of slime deposits is a major problem facing paper industries. The slime may be biological or nonbiological. Biological deposits that are composed of varied microflora along with fibers, fillers and dirt are the most troublesome. Slime producing microbes secrete extracellular polysaccharides that gum up the process machinery. The specific nature of slime and its formation depend on the mill environment. Correspondingly, countermeasures vary with the type of slime deposit. Conventional slime control methods generally employ combinations of biocides. This leads to effluent toxicity, as well as high processing and treatment costs. Therefore, alternative control measures are in demand. Once such measure is the use of enzymes (levanases) that dissolve the slime to some degree and improve biocide penetration into the slime layer. As a result, the amount of biocide required is reduced, process economics improve and effluent treatment is simplified.

Purification and properties of levanase from Rhodotorula sp.

Levanase, a slime dissolving enzyme of Rhodotorula sp., was purified to approx. 26-fold by ammonium sulphate precipitation, DEAE and gel filtration (Sephacryl S-200) chromatography. The molecular mass of the enzyme was 39 kDa. The purified levanase showed maximum activity at pH 6.0 and 40 degrees C. Enzyme was quite stable at 4 degrees C and at pH 5.5 to 6.5. Hg2+ at a level of 10 mM completely inhibited the levanase activity, while 2-mercaptoethanol at the same concentration showed a 2.93-times increase in activity. In addition to levan, the enzyme also showed substrate specificity towards inulin.

Production of levanase byRhodotorula sp.

Rhodotorula sp. produced a high yield of levanase (12.5 nkat/mL) in shake flasks in basal medium containing 1% maltose as the sole carbon source. Among the different carbon sources used, maltose was found to be the best for levanase production. The optimum temperature and pH for levanase production were 30°C and 6, respectively. In a batch reactor the enzyme productivity was higher (500 nkat L−1 h−1) than in shaken flasks (347 nkat L−1 h−1).