Insect gut microbiome - An unexploited reserve for biotechnological application

Metagenomics research has been developed over the past decade to elucidate the genomes of the uncultured microorganisms with an aim of understanding microbial ecology. On the other hand, it has also been provoked by the increasing biotechnological demands for novel enzymes, antibiotic and signal mimics. The gut microbiota of insects plays crucial roles in the growth, development and environmental adaptation to the host insects. Very recently, the insect microbiota and their genomes (microbiome), isolated from insects were recognized as a major genetic resources for bio-processing industry. Consequently, the exploitation of insect gut microbiome using metagenomic approaches will enable us to find novel biocatalysts and to develop innovative strategies for identifying smart molecules for biotechnological applications. In this review, we discuss the critical footstep in extraction and purification of metagenomic DNA from insect gut, construction of metagenomic libraries and screening procedure for novel gene identification. Recent innovations and potential applications in bioprocess industries are highlighted.

Proteolytic enzyme mediated antagonistic potential of Pseudomonas aeruginosa against Macrophomina phaseolina.

A new antagonistic bacterial strain PGPR2 was isolated from the mungbean rhizosphere and documented for the production of hydrolytic enzymes with antifungal activity. Based on the phylogenetic analysis of the 16S rRNA gene sequence and phenotyping, this strain was identified as Pseudomonas aeruginosa. Maximum protease activity (235 U/mL) was obtained at 24 h of fermentation. The protease was purified to homogeneity in three steps: ammonium sulphate precipitation, anion exchange chromatography on DEAE- cellulose resin and gel filtration chromatography using P6 column. The purified enzyme had a molecular weight of ~33 kDa. The purified protease exhibited maximum activity at pH 6.0 and retained 80% of activity in a pH range of 5.0 - 9.0. Proteolytic activity was maximum in a temperature range of 40–70 °C. However, the enzyme was stable at 40 °C for 60 min. Among the metals tested, Mg2+ enhanced the protease activity. Internal amino acid sequence of the protease obtained by MALDI -ToF and subsequent Mascot database search showed maximum similarity to the HtpX protease of P. aeruginosa strain PA7. Thus, by virtue of its early production time, thermostability and effective antifungal ability, the protease purified and characterized from P. aeruginosa PGPR2 has several potential applications as fungicidal agents in agriculture.

Biosynthesis and characterization of mercury sulphide nanoparticles produced by Bacillus cereus MRS-1.

Mercury is a highly toxic heavy metal accumulated in the environment, which can be detoxified by reducing Hg2+ to non toxic form. Bacteria resistant to toxic metals and capable of converting them into non toxic forms have a direct application in the bioremediation of contaminated sites. In this study, mercury resistant strain Bacillus cereus MRS-1 was isolated from electroplating industrial effluent. This strain exhibited the ability to convert mercury into extracellular sulphide nanoparticles of mercury. The recovered HgS nanoparticles have been characterized by UV-VIS spectrophotometer, FT-IR, atomic force microscopy, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, powder X-ray diffraction pattern and thermogravimetric analysis. The synthesized nanoparticles were spherical with a size range of 10–100 nm. This strain can be potentially exploited for the production of HgS nanoparticles as well as for detoxification of mercury in the environment without producing secondary pollution of mercury methylation or Hg (0) volatilization.

Differential expression of Zymomonas mobilis sucrase genes (sacB and sacC) in Escherichia coli and sucrase mutants of Zymomonas mobilis

Os genes do sacB e do sacC que codificam o levansucrase e o sucrase extracellular respectivamente foram sub-clonados independentemente no pBluescript (número elevado de cópias) e no vetor ponte para Z. mobilis-E. coli, pZA22 (baixo número de cópias). A expressão destes genes foi comparada tanto em E. coli quanto em Z. mobilis. O nível da expressão do gene sacB em E. coli foi quase dez vezes menor do que a expressão do gene sacC, independente do meio de cultivo ou da linhagem hospedeira. Em Z. mobilis, a expressão dos genes sacB e sacC mostrou regulação dependente da fonte de carbono. Os níveis dos transcritos sacB e sacC estavam três vezes mais aumentados em células cultivadas em sacarose do que aquelas cultivadas em glicose/frutose. A análise por Northern blot revelou que o nível do transcrito sacC era 2-3 vezes maior do que aquele de sacB. Esses resultados sugerem que a expressão do gene sacC foi mais pronunciada do que sacB.

Beta-fructofuranosidase production by 2-deoxyglucose resistant mutants of aspergillus niger in submerged and solid-state fermentation.

Aspergillus niger produces extracellular beta-fructofuranosidase under submerged (SmF) and solid state fermentation (SSF) conditions. After UV mutagenesis of conidiospores of A. niger, 2-deoxyglucose (10 g/l) resistant mutants were isolated on Czapek's minimal medium containing glycerol as a carbon source and the mutants were examined for improved production of beta-fructofuranosidase in SmF and SSF conditions. One of such mutant DGRA-1 overproduced beta-fructofuranosidase in both SmF and SSF conditions. In SmF, the mutant DGRA-1 showed higher beta-fructofuranosidase productivity (110.8 U/l/hr) than the wild type (48.3 U/l/hr). While in SSF the same strain produced 322 U/l/hr of beta-fructofuranosidase, 2 times higher than that of wild type (154.2 U/l/hr). In SmF, both wild type and mutants produced relatively low level of beta-fructofuranosidase in medium containing sucrose with glucose than from the sucrose medium. However in SSF, the DGRA-1 mutant grown in sucrose and sucrose+ glucose did not show any difference with respect to beta-fructofuranosidase production. These results indicate that the catabolite repression of beta-fructofuranosidase synthesis is observed in SmF whereas in SSF such regulation was not prominent.