Water miscible mono alcohols effect on the structural conformation of Bacillus clausii GMBAE 42 serine alkaline protease

Decitabine bioproduction using a biocatalyst with improved stability by adding nanocomposites

A novel IDA-LaNDT derivative was able to reach the highest productivity in the biosynthesis of a well-known antitumoral agent called decitabine. However, the combination of two simple and inexpensive techniques such as ionic absorption and gel entrapment with the incorporation of a bionanocomposite such as bentonite significantly improved the stability of this biocatalyst. These modifications allowed the enhancement of storage stability (for at least 18 months), reusability (400 h of successive batches without significant loss of its initial activity), and thermal and solvent stability with respect to the non-entrapped derivative. Moreover, reaction conditions were optimized by increasing the solubility of 5-aza by dilution with dimethylsulfoxide. Therefore, a scale-up of the bioprocess was assayed using the developed biocatalyst, obtaining 221 mg/L·h of DAC. Finally, green parameters were calculated using the nanostabilized biocatalyst, whose results indicated that it was able to biosynthesize DAC by a smooth, cheap, and environmentally friendly methodology.

Cloning, Expression, and Characterization of a Novel Thermostable and Alkaline-stable Esterase from Stenotrophomonas maltophilia OUC_Est10 Catalytically Active in Organic Solvents

A thermostable and alkaline-stable novel esterase (Est7) was identified through the whole genome sequencing of Stenotrophomonas maltophilia OUC_Est10. The open reading frame of this gene encoded 617 amino acid residues. After heterologous expression in Escherichia coli BL21 (DE3), the purified Est7 was separated as a single protein and presented a molecular mass of 70.6 kDa. Multiple sequence alignment indicated that Est7 had a typical catalytic triad (Ser-Asp-His) and the conserved sequence (GDSL) typical of the family II lipid hydrolase proteins. Est7 showed good stability in alkaline buffers, especially in Tris-HCl buffer at pH 9.0 (residual activity 93.8% after 96 h at 4 °C) and in the medium temperature conditions (residual activity 70.2% after 96 h at 45 °C and pH 8.0). The enzyme also retained higher stability toward several hydrophilic and hydrophobic organic solvents (e.g., after incubation in 100% acetonitrile or in n-hexane the enzyme retained about 97% and 84% of the activity in the absence of organic solvent, respectively). Furthermore, Est7 could catalyze the transesterification reaction of vinylacetate with 2-phenylethanol and cis-3-hexen-1-ol to their corresponding acetate esters in petroleum ether or tert-butyl methyl ether. These results indicate Est7 as a promising biocatalyst for applications of Est7 in non-aqueous media.

Inoculation and alkali coeffect in volatile fatty acids production and microbial community shift in the anaerobic fermentation of waste activated sludge

Batch fermentations of waste activated sludge (WAS) at alkaline pH with different inocula were performed. Paper mill anaerobic granular sludge (PAS) and dyeing mill anaerobic sludge (DAS) were used as inocula. At pH 10 the inoculation did not increase the volatile fatty acids (VFAs) production compared to the non-inoculated samples fermented in the same conditions, and the maximal VFAs yield of non-inoculated WAS was higher than inoculated WAS. However, at pH 9 the inoculation with PAS increased the sludge hydrolysis and VFAs production was 1.7-fold higher than that in non-inoculated WAS (yield 52.40mg/g of volatile solid). Denaturing gradient gel electrophoresis analysis revealed that 3 bacterial species, identified as Proteocatella, Tepidibacter, and Clostridium, disappeared when inoculated with PAS at pH 9 or at pH⩾10. The results showed that the inoculation with PAS can be helpful to achieve a relatively high VFAs production from WAS in a moderate alkaline environment.

Water miscible mono alcohols' effect on the proteolytic performance of Bacillus clausii serine alkaline protease

In this study, our investigations showed that the increasing concentrations of all examined mono alcohols caused a decrease in the Vm, kcat and kcat/Km values of Bacillus clausii GMBE 42 serine alkaline protease for casein hydrolysis. However, the Km value of the enzyme remained almost the same, which was an indicator of non-competitive inhibition. Whereas inhibition by methanol was partial non-competitive, inhibition by the rest of the alcohols tested was simple non-competitive. The inhibition constants (KI) were in the range of 1.32-3.10 M, and the order of the inhibitory effect was 1-propanol>2-propanol>methanol>ethanol. The ΔG(≠) and ΔG(≠)E-T values of the enzyme increased at increasing concentrations of all alcohols examined, but the ΔG(≠)ES value of the enzyme remained almost the same. The constant Km and ΔG(≠)ES values in the presence and absence of mono alcohols indicated the existence of different binding sites for mono alcohols and casein on enzyme the molecule. The kcat of the enzyme decreased linearly by increasing log P and decreasing dielectric constant (D) values, but the ΔG(≠) and ΔG(≠)E-T values of the enzyme increased by increasing log P and decreasing D values of the reaction medium containing mono alcohols.

One-step enzymatic synthesis of nucleosides from low water-soluble purine bases in non-conventional media

The effect of several water-miscible cosolvents on activity and stability of soluble and immobilized 2'-deoxyribosyltransferase from Lactobacillus reuteri on Sepabeads® has been studied in order to establish optimal conditions for enzymatic synthesis of nucleosides using purine bases with low solubility in aqueous buffer. As a rule of thumb, there was a general reduction of soluble enzyme activity when cosolvent content was gradually increased in reaction medium. In contrast, immobilized enzyme activity was enhanced 1.2-1.4-fold at 20% of methanol, ethanol, 2-propanol, diethylene glycol, and acetone; and at 10% and 30% acetonitrile. Likewise, highest increased activity (1.8-fold) was also obtained in presence of 20% acetonitrile. Immobilized enzyme was successfully used in the synthesis of 2'-deoxyxanthosine and 2'-deoxyguanosine using 2'-deoxyuridine as sugar donor and the corresponding poor water-soluble base in the presence of 30% of methanol, ethanol, 2-propanol, ethylene glycol, acetonitrile, and DMSO, giving high nucleoside yields at 4h.