Strategy for Rapid Recovery of Simultaneous Sulfide and Nitrite Removal under High Substrate Inhibition

The paper deals with the strategy for a quick recovery of reactor treating sulfide and nitrite simultaneously under inhibition caused by high substrate concentration. For influent sulfide concentration of 360 mg S/L, respective sulfide and nitrite removal percentages dropped to 74.19% and 14.33% due to inhibition caused by high sulfide and nitrite concentrations. It was found that reduction in the influent substrate concentration (300 mg S/L) could not revive the nitrite removal performance in 4 days’ operation, which still showed a declining tendency from 47.16–18.52%. Regulating the influent pH around 6.70 ± 0.10, it only took 4 days to recover the performance for 300 mg S/L. Furthermore, at influent sulfide concentration increased to 360 mg S/L, respective sulfide and nitrite removal percentages were 99.76 ± 0.27% and 100%. The strategy of regulating influent pH could recover the process performance in a short term, which would provide great convenience for subsequent process research.

Direct Cross-Coupling of Alcohols with O-Nucleophiles Mediated by N-Iodosuccinimide as a Precatalyst under Mild Reaction Conditions

We report N-iodosuccinimide as the most efficient and selective precatalyst among the N-halosuccinimides for dehydrative O-alkylation reactions between various alcohols under high-substrate concentration reaction conditions. The protocol is non-metal, one-pot, selective, and easily scalable, with excellent yields; enhancing the green chemical profiles of these transformations.

N-Halosuccinimides as Precatalysts for C-, N-, O-, and X-Nucleophilic Substitution Reactions of Alcohols under Mild Reaction Conditions

N-halosuccinimides (chloro, bromo, and iodo, respectively) were introduced, tested, and applied as efficient and non-metal precatalysts for C-, N-, O-, and X-nucleophilic substitution reactions of alcohols under solvent-free reaction conditions (SFRC) or under high substrate concentration reaction conditions (HCRC) efficiently and selectively, into the corresponding products.

Using Choline Chloride-Based DESs as Co-Solvent for 3,5-Bis(trifluoromethyl) Acetophenone Bioreduction with Rhodococcus erythropolis XS1012

(S)-3,5-Bistrifluoromethylphenyl ethanol((S)-BTPE) is a key pharmaceutical intermediate of the NK-1 receptor antagonist. The asymmetric bioreduction of 3,5-bis(trifluoromethyl) acetophenone (BTAP) to (S)-BTPE using Rhodococcus erythropolis XS1012 has been established in a phosphate buffer system. To overcome the problem of unsatisfactory yields at high substrate concentration, deep eutectic solvents (DESs) have been introduced to the buffer system. After screening 13 kinds of choline chloride-based DESs, [choline chloride][urea] ([ChCl][U]) showed great influence on the cell activity and significantly increased the cell membrane permeability. Subsequently, some major parameters for this reaction were determined. A remarkable (S)-BTPE yield of 91.9% was gained at 150 mM substrate concentration under optimized reaction conditions with >99.9% product enantioselectivity. Compared to reduction in a buffer system, the developed [ChCl][U]-containing system increased the yield from 82.6% to 91.9%. It maintains a yield of 80.7% with the substrate concentration up to 300 mM, compared to only 63.0% in buffer system. This study demonstrated that [ChCl][U] is a feasible co-solvent to improve the bioreduction process.

KARAKTERISTIK DAN SIFAT KINETIKA ENZIM KITINASE ASAL JAMUR ENTOMOPATOGEN Beauveria bassiana

Characteristics and Kinetics of Chitinase Enzyme from Entomopathogenic Fungus Beauveria bassianaBeauveria bassiana is one of the entomopathogenic fungi that produces chitinase when infecting the host. Chitinase is widely used as biocontrol agents because it can degrade chitin into an environmentally friendly product. This study aims to characterize and test the kinetics of chitinase from B. bassiana. This characterization includes determination of pH and optimum temperature, enzyme stability and enzyme kinetics test by determining Km and Vmax value with Lineweaver-Burk equations. The result of experiment showed that the chitinase B. bassiana had pH and optimum temperature of 5 and 40ºC respectively. This enzyme was stable until 90 minutes incubation at 40ºC. The Km and Vmax values were 0.181 mg/L and 0.022 mg/L.sec respectively. The Km value is higher than Vmax, which means the affinity of the enzyme to the lower substrate requiring high substrate concentration to increase the reaction rate. It can be concluded that the chitinase activity of B. bassiana is still low.Keywords: Beauveria bassiana, characteristics and kinetics, chitinase enzyme, entomopathogenic, Lineweaver-BurkABSTRAKBeauveria bassiana merupakan salah satu jamur entomopatogen yang memproduksi kitinase saat menginfeksi inangnya. Enzim kitinase saat ini banyak digunakan sebagai agen biokontrol karena dapat mendegradasi kitin menjadi produk yang ramah lingkungan. Penelitian ini bertujuan untuk mengkarakterisasi dan menguji kinetika enzim kitinase asal jamur B. bassiana. Metode yang digunakan dalam karakterisasi ini mencakup penentuan pH dan suhu optimum, kestabilan enzim pada suhu optimumnya, dan uji kinetika enzim yang mencakup penentuan nilai Km dan Vmaks dengan persamaan Lineweaver-Burk. Hasil penelitian karakterisasi menunjukkan bahwa enzim kitinase B. bassiana mempunyai pH dan suhu optimum masing-masing 5 dan 40ºC. Enzim ini stabil sampai pada 90 menit inkubasi pada suhu 40ºC. Nilai Km diperoleh 0,181 mg/L dan Vmaks sebesar 0,022 mg/L.detik. Nilai Km lebih tinggi daripada Vmaks, yang artinya afinitas enzim terhadap substrat rendah sehingga membutuhkan konsentrasi substrat yang tinggi untuk meningkatkan kecepatan reaksi, maka dapat disimpulkan bahwa aktivitas kitinase dari B. bassiana masih tergolong rendah.Kata kunci: Beauveria bassiana, entomopatogen, enzim kitinase, karakteristik dan kinetik, Lineweaver-Burk

Effect of Substrate Feeding Concentration on Initial Biofilm Development in Anaerobic Hybrid Reactor

To elucidate the effect of substrate concentration on biofilm development, glucose concentrations of 500 and 1,000 mg/L were used. At an early stage, biofilm development at both concentrations was not significantly different (P=0.621). After removing suspended biomass at 24 operational hours, the biofilm development at high substrate concentration was higher than at lower concentration. At 72 operational hours, the amounts of attached biomass at low and high glucose feeding were 9.04±1.17 and 28.58±2.72 g VSS/m2, respectively. The activities of acidogens, acetogens, and methanogens at the low glucose concentration were 0.334, 0.016 and 0.003 g COD/g VSS/h, and those at the high glucose concentration were 0.145, 0.003 and 0.001 g COD/g VSS/h, respectively. Moreover, the ratio of methanogenic activity at low glucose concentration was higher than at high glucose concentration. The glucose utilization at low and high feeding concentrations was 33% and 27%, respectively. These results indicated that rapid biofilm development by using high substrate concentration would be less beneficial if unbalance of methanogenic ratio was found in biofilm.