Effect of passivated iron powder on final-product distribution in Fe-supported denitrification

An integrated nitrate treatment using passivated iron powder (PIP) and Alcaligenes eutrophus, which is a kind of hydrogenotrophic denitrifying bacteria, was conducted to investigate the effect of iron oxide coating on final-product distribution in hydrogenotrophic denitrification. Based on the results, the autotrophic denitrification supported by PIP could completely remove about 50 mg·L−1 of nitrate within 4 days, and almost 80% of nitrate was changed into N2O (under acetylene blocking) without residual nitrite or ammonium. While only 53% of the nitrate was removed using acid-washed iron (AWI) instead of PIP, about 70% was converted into ammonium. Furthermore, a layer of FeOOH converted from hematite (α-Fe2O3) and magnetite (Fe3O4), which may block direct chemical nitrate reduction, was observed on the iron surface when PIP was used to support hydrogenotrophic denitrification. In addition, increasing pH from 5 to 8 increased nitrite generation from 1.19 to 4.91%, and decreased ammonium formation from 4.23 to 0%.

Novel gut bacterial fauna of Gryllotalpa africana Beau. (Orthoptera : Gryllotalpidae)

Gryllotalpa africana (Beauvois) is a successful group of detritus feeder therefore it is an important both for their roles in carbon cycling in the environment and converting organic decaying material in to biofuel. Hence, bacterial diversity and relationship were explored from the mole cricket G.africana (Beau) to show ideal symbiotic association. The analysis and characterization of gut micro biota of G.africana (Beau) revealed the presence of 10 species and two genera of bacteria viz. Acidiphilium rubrum, Dienococcus proteolyticus, Sporosarcina ureae, Micrococcus varians, Micrococcus kristinae, Acetobactrium, Alcaligenes eutrophus, Micrococcus roseus, Micrococcus lylae, Sporosarcina, Citrobacter amalonaticus and Corynebacterium xerosis. All the species and genera were confirmed by observing their morphological features of the colony and various biochemical tests. These results indicate that the presence of mole cricket specific bacterial lineages implies relationship of gut microbes and their host mole cricket. The outcome of this work indicted that the gut bacterial fauna of G.africana shows the species-rich with greater diverse communities which might be providing resistance to invasion of pathogenic bacteria. DOI: http://dx.doi.org/10.3126/ijls.v6i1.5949

Toxicity of Fe0 Nanoparticles on the Denitrifying Bacteria-Alcaligenes Eutrophus

The bio-toxicity of Fe0 nanoparticles on the denitrifying bacterial- Alcaligenes eutrophus was detected by the two methods of detecting inhibition of the growth of microorganisms and nitrification inhibition rate. The results showed that Fe0 nanoparticles had obvious toxicity on the growth and nitrification inhibition rate. Besides, there had distinct relationship between dose and toxicity of Fe0 nanoparticles. Meanwhile, we also studied effects of different kinds of Fe0 nanoparticles on microorganism, including bimetallic nanoparticles(nano Fe–Ni) and coated iron nanoparticles (sodium oleate–Fe0nanoparticles). We detected that the bio-toxicity of these three Fe0 nanoparticles followed the sequence of Ni-containing nanoparticles>unmodified NZVI>the sodium oleate–Fe0 nanoparticles. In conclusion, Fe0 nanoparticles had visible toxicity on the denitrifying bacterial, but we can decrease the toxicity of Fe nanoparticles by surface coating and decoration of nano-metal materials.

EFEKTIVITAS EKSTRAK PICUNG (P.edule Reinw) YANG DIKERINGKAN DENGAN BAHAN PENGISI SERBUK GERGAJI DALAM PENGAWETAN IKAN

Biji picung (Pangium edule Reinw) telah terbukti dapat digunakan untuk mengawetkan ikan. Namun demikian, cara penggunaan picung secara tradisional, dengan menaburkan cacahan biji picung segar dianggap kurang praktis, dan ketersediaannya terkendala oleh musim. Ekstrak biji picung juga sudah teruji dapat menghambat pertumbuhan bakteri gram negatif dan positif. Pada penelitian ini dicoba mengawetkan ikan segar menggunakan bubuk picung yang dibuat dari ekstrak picung yang telah dikeringkan menggunakan serbuk gergaji sebagai bahan pengisi. Biji picung segar yang telah dicacah dimaserasi menggunakan pelarut air, etanol 50%, dan etanol 80%. Setelah maserasi dilakukan penyaringan dan penambahan serbuk gergaji kering steril, lalu dikeringkan kembali dalam oven pada suhu 40ºC. Bubuk picung kemudian diaplikasikan pada ikan kembung segar dengan perbandingan 6% (b/b) dan disimpan pada suhu kamar untuk diamati pH, TVB, dan jumlah bakterinya. Untuk mendukung penelitian ini, dilakukan uji aktivitas antibakteri dari bubuk picung terhadap 2 jenis bakteri gram positif (Microccus luteus dan Staphylococcus aureus) serta 2 jenis bakteri gram negatif (Alcaligenes eutrophus dan Enterobacter aerogenes). Hasil penelitian menunjukkan bahwa dari nilai pH, TVB, dan jumlah bakteri yang diperoleh, ternyata bubuk picung dari semua perlakuan tidak mampu menghambat pembusukan ikan sebesar daya pengawetannya dalam bentuk segar. Dari hasil uji aktivitas antibakteri terbukti bahwa bubuk picung hanya mampu menghambat bakteri gram positif. Adapun bakteri gram negatif, yang merupakan penyebab pembusukan ikan, tidak dapat dihambat. Hal ini kemungkinan disebabkan cara pengeringan belum cukup baik sehingga zat pengawet dalam biji picung tidak mampu menembus dinding sel bakteri gram negatif yang terdiri atas dua lapisan, yaitu lipopolisakarida-protein dan peptidoglikan, yang memang lebih sulit untuk ditembus oleh antibiotika, desinfektan, dan senyawa kimia lain. Untuk itu riset masih harus diteruskan dengan cara pengeringan yang tidak menurunkan kemampuan daya antibakteri dari biji picung.